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fOURN A OF GEOLOGY,
Serve
Vals,
Moti NAL OF GEOLOGY
A Semi-Quarterly Magazine of Geology and Related Sciences
EDITORS T. C. CHAMBERLIN, zz General Charge
R. D. SALISBURY R.A] ES PENROSE, JR.
Geographic Geology Economic Geology J. P. IDDINGS ¢, R. VAN HISE
Petrology Structural Geology STUART WELLER W. H. HOLMES
Paleontologic Geology Anthropic Geology
S. W. WILLISTON, Vertebrate Paleontology ASSOCIATE EDITORS
SIR ARCHIBALD GEIKIE G. K, GILBERT
Great Britain Washington, D. C. H. ROSENBUSCH H. S. WILLIAMS
Germany ; Cornell University CHARLES BARROIS Cy Da WALCOTT
France U.S. Geological Survey ALBRECHT PENCK J. C. BRANNER
Germany Stanford University HANS REUSCH W. B. CLARK
. Norway Johns Hopkins University
GERARD DE GEER O. A. DERBY
Sweden Brazil
T. W. E. DAVID Australia
LEE TR &~\eonlan Insti: > “eg j Utus i
WOEIIIM OES 20
CHICAGO Che Anibersity of Chicago Press 1907
Published February, March, May, June, August, September, November, December, 1907
_ Composed and Printed By | The University of Chicago Press Chicago, Illinois, U. S. A.
CONPDENLS. OF VOLUME XV
NUMBER I
A DRAINAGE PECULIARITY OF THE SANTA CLARA VALLEY AFFECTING FRESH-WATER Faunas. J. C. Branner
ON THE PROBABLE GLACIAL ORIGIN OF CERTAIN FOLDED SLATES IN SOUTH- ERN ALASKA. Eliot Blackwelder
NOTES ON GLACIATION IN THE SANGRE DE Cristo RANGE, COLORADO. C. E. Siebenthal
‘THE PLACE OF ORIGIN OF THE MOON—THE VOLCANIC PROBLEM. William H. Pickering
THe DOUBLE CREST OF SECOND WAtTCHUNG MountTaIN. J. Volney Lewis
SECTION OF THE MANtIus LIMESTONE AT THE NORTHERN END OF THE HELDERBERG PLATEAU. Charles S. Prosser
NOTES ON THE RED BEDS OF THE RIO GRANDE REGION IN CENTRAL NEW Mexico. Willis T. Lee
STUDIES IN THE DEVELOPMENT OF CERTAIN PALEozorc Corats. C. E.
Anderson EDIRORTAD. a CG, REVIEWS
NUMBER II
THE DEVONIAN SECTION OF ITHACA, N. Y. Part II. THe Discrrt- NATION OF THE NUNDA-CHEMUNG BounpbarRy. Henry Shaler Williams
ABRASION BY GLACIERS, RIVERS, AND WAVES. Lewis G. Westgate THE SKULL OF PALEORHINUS. J. H. Lees
THE CRYSTALLINE ROCKS OF THE OAK Hitt AREA NEAR SAN Toner CALI- FORNIA. E. P. Carey and W. J. Miller
SOME OBSERVATIONS ON THE MOVEMENTS OF UNDERGROUND WATER IN CONFINED Basins. A. R. Schultz
EDITORIAL REVIEWS .
PAGE
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23 39
46
52
59 70 73
93 113
121 152 170
182 187
vl CONTENTS OF VOLUME XV
NUMBER III
REPORT OF A SPECIAL COMMITTEE ON THE CORRELATION OF THE PRE-CAM- BRIAN ROCKS OF THE ADIRONDACK MOUNTAINS, THE “‘ORIGINAL LAv- RENTIAN AREA” OF CANADA AND EASTERN ONTARIO. F. D. Adams and Others
THE SEDIMENTARY BELT OF THE Coast OF BRaziL. Orville A. Derby
REDISTRIBUTION OF ELEMENTS IN THE FORMATION OF SEDIMENTARY ROCKS. Warren J. Mead
THE FoRMATION OF LEUCITE IN IGNEOUS Rocks. Henry S. Washington . Tuomas Conpon. Chester W. Washburne Rea te AEGIRITE AND RIEBECKITE RocKs FROM OKLAHOMA. Austin F. Rogers .
STUDIES FOR STUDENTS: THE RECENT ADVANCE IN SEISMOLOGY. William Herbert Hobbs
REVIEWS .
NUMBER IV
THE MetamorpHic Cycie. C. K. Leith
Nores ON THE PALEOzoIC FAUNAS AND STRATIGRAPHY OF SOUTHEASTERN AtasKa. E. M. Kindle ; ; : eis.
CONTRIBUTIONS TO THE PLEISTOCENE FLORA oF NorTH CAROLINA. Edward W. Berry .
Tue GIRDLES AND Hinp Limp oF HotosAurus ABRuUpTUS MArsH. S..R. Capps, Jr. si ames
THE ForMATION oF LEucITE IN IcNEous Rocks—Continued. Henry S. Washington go iterate Me i es tay Seamed
STUDIES FOR STUDENTS: THE RECENT ADVANCE IN SEISMOLOGY. William
Herbert Hobbs Epritormts. T.C. C. [INS NORE Shere AA RER Te Re See een ee Nat a eee eR O, REVIEW NUMBER V
GLACIAL FEATURES OF THE ALASKAN COAST BETWEEN YAKUTAT BAY AND THE ALSEK River. Eliot Blackwelder
STRATIGRAPHY AND STRUCTURE OF THE Park City Mininc District, UTAH. J. M. Boutwell
PAGE
303 314 338 350 357 396
AII
412
415
434
CONTENTS OF VOLUME XV
RESTORATIONS OF CERTAIN DEVONIAN CEPHALOPODS WITH DESCRIPTIONS or NEW SPECIES 3 : : 5
_ DISCOVERY OF CAMBRIAN ROCKS IN SOUTHEASTERN CALIFORNIA. N. H. Darton ; : : : ; ;
SomE Notes ON SCHIST-CONGLOMERATE OCCURRING IN GEORGIA. S. W. McCallie . : 5
ON AN OCCURRENCE OF CORUNDUM AND DUMORTIERITE IN PEGMATITE IN Cotorapo. George I. Finlay
GLACIAL Rock Sripinc. F. O. Jones :
VALLEY DEPENDENCIES OF THE SCIOTO ILLINOIAN ee IN wii County, Onto. Frank Carney
REVIEWS .
RECENT - PUBLICATIONS
NUMBER VI THe PrE-RICHMOND UNCONFORMITY IN THE MISSISSIPPI VALLEY. Stuart Weller
ON THE ORIGIN AND DEFINITION OF THE GEOLOGIC TERM ‘‘ LARAMIE.” A. C. Veatch
THE CHARACTERISTICS OF VARIOUS TYPES OF CONGLOMERATES. George R. Mansfield .
RESTORATION OF DIADECTES. E. C. Case DoME STRUCTURE IN CONGLOMERATE. Ralph Arnold .
PRE-WISCONSIN DRIFT IN THE FINGER LAKE REGION oF NEW YORK. - Frank Carney
THE GLENEYRIE FORMATION AND ITs BEARING ON THE AGE OF THE FOUN- TAIN FORMATION IN THE MANITOU REGION, CoLorADo. George I. Finlay sie) See Ri Sees eRe nT
THE HAMILTON IN Onto. Clinton R. Stauffer
REVIEWS .
RECENT PUBLICATIONS
NUMBER VII PERMO-CARBONIFEROUS CLIMATIC CHANGES IN SouTH AMERICA. David WHITE
STRATIGRAPHIC RESULTS OF A RECONNAISSANCE IN WESTERN COLORADO AND UTAH. Whitman Cross
vu
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479 485
488
496 511
519 526 552 556 560 571 586
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597 610
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vill CONTENTS OF VOLUME XV
NOTES ON THE GEOLOGICAL SECTION OF MICHIGAN. Part I. THE PRE- OrpoviciAN. A.C. Lane and A. E. Seaman .
NOTES ON THE JAMAICA EARTHQUAKE. Myron L. Fuller GLACIAL EROSION IN LONGITUDINAL VALLEYS. Frank Carney REVIEWS .
NUMBER VIII THE WITWATERSRAND GOLD REGION, TRANSVAAL, SOUTH AFRICA, AS SEEN IN RECENT Mininc DEVELOPMENTS. R. A. F. Penrose, Jr.
METAMORPHISM BY COMBUSTION OF THE HYDROCARBONS IN THE OIL- BEARING SHALE OF CALIFORNIA. Ralph Arnold and Robert Ander- son
THE SUDBURY LAccCOLITHIC SHEET. A. P. Coleman . THE COMPOSITION OF THE RED CLaAy. F. W. Clarke ; THE GLACIATION OF THE Urtnta Mountains. Wallace W. Atwood .
NOTES ON THE PENNSYLVANIAN FORMATIONS IN THE R10 GRANDE VALLEY, New Mexico. C.H. Gordon .
EDITORIALS REVIEWS . RECENT PUBLICATIONS
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THE
IOURNAL OF CEOLOGY
JANUARY-FEBRUARY 1907
A DRAINAGE PECULIARITY OF THE SANTA CLARA VALLEY AFFECTING FRESH-WATER FAUNAS
J. C. BRANNER
In 1890 Professor Joseph Le Conte read before the Geological Society of America an article on Tertiary and post-Tertiary changes of the Atlantic and Pacific coasts, in which he expressed the opinion that the drainage of the great valley of California formerly flowed into the Pacific Ocean, not through the Golden Gate as it does now, but by way of the Santa Clara Valley and the Bay of Monterey.‘ His reasons for this theory are: (1) that there is no submerged channel off the Golden Gate; (2) that there is a submerged valley off the Bay of Monterey, while (3) the watershed between the north end of the Santa Clara Valley and that now flowing into Monterey Bay by way of the Pajaro River is less than a hundred feet high at its lowest point. A few years later Dr. C. H. Gilbert, professor of zodlogy at Stanford University, in studying the fishes of California, observed a remarkable resemblance between certain fishes found in the Sacra- mento drainage and in the streams flowing into the Bay of San Fran- cisco, and those found in the Pajaro, Salinas, San Lorenzo, and other streams flowing into the Bay of Monterey. ‘The fishes here referred to are not of kinds that descend into salt water; their present distribution therefore cannot be explained by that kind of migration. It can only be accounted for by some ancient direct connection between the streams in question. ‘This work has been greatly extended by
t Bulletin of the Geological Society of America, Vol. II (1891), p. 326.
Vol. XV, No. 1 I
2 J. C. BRANNER
Professor Snyder, of the Department of Zodlogy, Stanford Uni- versity. ?
In accounting for the distribution of these fishes, the theory of Dr. Le Conte seemed to meet the requirements of the case fairly well. To understand the principal peculiarities of this fauna, it was only necessary to imagine the Golden Gate closed and the Sacra- mento Valley drainage flowing down the Santa Clara Valley and emptying into the Bay of Monterey. The Bay of San Francisco would thus be a body of fresh water, and the fishes of the upper Sacra- mento could ascend streams flowing into the fresh-water bay and into the Santa Clara Valley. There is some difficulty in comprehending how the fishes from the Pajaro, through which the waters are sup- posed to have entered the Bay of Monterey, could get into the Salinas a few miles to the south, and into the San Lorenzo which enters the bay twelve miles or more northwest of the mouth of the Pajaro; but no stress need be laid just now on the relation of the Pajaro to other streams flowing into the Bay of Monterey. Recent study of the geology southwest of San José has raised serious doubt regarding Dr. Le Conte’s conclusions and necessitated a closer scrutiny of the facts offered in their support.
The first two reasons brought forward by him—namely, (1) that there is no submerged channel in front of the Golden Gate, and (2) that there is such a channel in the Bay of Monterey—are sufficiently warranted by the hydrographic charts. ‘The Monterey channel is clearly exhibited in one of the charts accompanying Professor George Davidson’s ‘Submerged Valleys of the Coast of California,’ published in the Proceedings of the California Academy oj Sciences, Third Series, Vol. I, pp. 73-101, 5. F. 1897. The question is here raised, however, regarding the assumed height of the watershed in the Santa Clara Valley between the drainage into the Bay of San Francisco and the drainage into the Bay of Monterey. Dr. Le Conte says it is less than a hundred feet above sea-level, and it is apparently assumed that with the Golden Gate closed the drainage of the great valley would rise and flow over this notch and pass down the Pajaro River to the Bay ot Monterey.
2 J. O. Snyder, ‘Notes on the Fishes of the Streams Flowing into San Francisco Bay, Cal.,”” Report of the U. S. Fish Commission, 1904.
DRAINAGE OF THE SANTA CLARA VALLEY 2
The line of the Southern Pacific Railway passes over the water- shed referred to at Madrone station, and the elevation at that place, as officially published, is 345 feet.t ‘This elevation, though much greater than was supposed, would not alone, however, seriously inter- fere with Dr. Le Conte’s theory. But if we imagine the Golden Gate closed, it is necessary, in order to test the validity of the hypothesis, to know where the lowest gaps are through which the water could escape to the sea. If the Madrone saddle, even with an elevation of 345, is the lowest pass to the ocean, then of course the water would flow out that way. But the Coast Survey’s topographic map of San Francisco shows that, if the present Golden Gate were closed and the water compelled to find a new outlet, it would first flow over the divide at Colma seven miles south of the City Hall of San Fran- cisco; this gap has an elevation of only 190 feet above tide. North of San Francisco it would also flow into the sea from Richardson Bay near Sausalito by way of Elk Valley, which has a watershed only 190 feet above tide-level.
Without further inquiry into the existence of other low divides between the bay and the ocean, it is evident that, even if it were admitted that the Golden Gate be a late topographic development, the Sacramento drainage did not lately flow into the Bay of Monterey by way of the Santa Clara Valley. It is evident also that the resem- blance between the fish faunas of the Sacramento drainage and the streams flowing into Monterey Bay must be sought elsewhere.
The accompanying map shows in a general way the present drain- age of the Santa Clara Valley in the vicinity of Madrone. Attention is directed to Coyote Creek, which emerges from the Mount Hamilton range opposite Madrone station and flows northwestward into the Bay of San Francisco. This stream, above where it emerges from the hills on to the plains, drains an area of 214 square miles, much more than any other one stream that enters the Santa Clara Valley. From the mouth of the gorge where this creek debouches on the plain a great alluvial fan spreads out toward the south and west across the entire width of the Santa Clara Valley, at this place a distance of two and a half miles. This fan forms the watershed in the valley trough between the Bay of San Francisco and the Pajaro River or
t Gannett’s Dictionary of Elevation, p. 220.
4 J. C. BRANNER
fF. Hamilton.
Fic. 1.—Map showing the relations of the drainage about the Bay of San Fran- cisco and the Bay of Monterey. The more heavily shaded areas represent the flat valley lands.
DRAINAGE OF THE SANTA CLARA VALLEY 5
the Bay of Monterey. Madrone station on the Southern Pacific Railway is at the southwestern edge of this alluvial fan, and is on the watershed at its lowest point. It will be seen from the map that upon emerging from the hills Coyote Creek bends sharply to the right and flows close to Las Animas Hills for several miles. ‘The configura- tion of the materials of the alluvial fan at the mouth of the gorge shows that the Coyote has been shifting its channel of late. A ter- race south of the stream, and approximately parallel with it, shows that it formerly flowed toward the west, while another and still higher terrace farther south shows that at an earlier date it flowed toward the southwest; and the general form of the alluvial fan shows that the whole fan was built by the Coyote. It is a characteristic feature of streams, in the building-up of such deposits, that they swing from side to side, flowing down over their own deposits in every direction, and shifting their channels as they become choked up by the deposit of their excess of load. The depth and position of the channel through which the Coyote now flows after emerging from the hills show. that there has been no recent discharge of its waters toward the Pajaro. ‘The general topography of the region about the mouth of the gorge suggests that the alluvial fan was built up a long while ago, and at a period when the stream was much more active than it now is—possibly during or toward the close of the glacial epoch. During the glacial epoch the streams of the region were much more vigorous than they have been since, for the coast stood at an elevation of two thousand feet or more higher than it does at present. There was therefore a greater precipitation, and during the winter months the Mount Hamilton Range must have been covered with snow which accumulated more than it does now and went off rather suddenly with the warm rains of early spring, producing much greater floods than we now have.
It follows from the form of this alluvial fan on the plain where the stream emerges from the mountains that the Coyote must have shifted from side to side in the usual fashion, especially in the early history of the alluvial cone and during the constructive period. It flowed sometimes toward the northwest, draining into the Bay of San Francisco, and at other times toward the southeast, draining through the Pajaro into the Bay of Monterey. Such a shifting of
6 J. C. BRANNER
the Coyote at the summit of the watershed would, in this fashion, afford an opportunity for the mingling of the fauna of the Pajaro and its tributaries with that of Coyote Creek and its tributaries. Fishes from the Pajaro could ascend the stream into the mountains while the water flowed toward the Pajaro, and when the stream shifted, or its waters divided, these fish could descend the Coyote. *
But the problem of the mingling of the fish faunas is not confined to the Pajaro and Coyote alone; it extends to the Sacramento and other streams flowing into the Bay of San Francisco and to other streams flowing into the Bay of Monterey. So long as the Bay of San Francisco is filled with salt or brackish water it is an effective barrier against the passage of these fishes.
The additional requirements of the case seem to be met by the theory of a former elevation of the coast. Indeed, not only does such a theory afford a satisfactory explanation of the mingling of the fish faunas of the streams under consideration, but it is necessary for the explanation of other phenomena more or less directly con- nected with this subject. That there was such an elevation is shown not only by (1) the mingling of the fish faunas of the streams referred to, and which I am unable to account for in any other way; but also by (2) the greater activity of the streams of the coast at a period not far removed geologically; by (3) the submerged valleys along the coast; and by (4) the islands off the California coast.
It is not proposed to discuss these evidences at length, but a few words may be said of the importance of each one. ‘The evidence of greater activity of the streams is not confined to the Coyote or to the streams of any particular district, but it is common to the streams of the Coast Range and of the Sierra Nevada. The great alluvial cones of the glacial epoch are far beyond the reach of the modern
1 The topographic peculiarity here cited is not unique. In 1892 Dr. B. W. Ever- man, in connection with the work of the U. S. Fish Commission, pointed out how fish may cross over the continental divide from the Columbia River basin to the Mississippi basin by way of Two-Ocean Pass. There isa similar low alluvial fan in a meadow on the watershed between the drainage of the Paraguay and of the Amazon basin. In both of these cases the watersheds permit the mingling of the existing fauna. (The Report of the Commissioner of Fish and Fisheries respecting the Establishment of Fish Cultural Stations in the Rocky Mountain Region and Gulf States, Miscellaneous Senate Document, No. 65, pp. 22-26 [Washington, 1892].)
DRAINAGE OF THE SANTA CLARA VALLEY 7.
streams which are now cutting into them. In the Santa Clara Valley every considerable stream that enters it, whether from the Mount Hamilton or the Santa Cruz range, has a broad alluvial fan where it emerges on the plain. ‘The same thing is true of the streams flowing into the San Joaquin Valley, whether from the Mount Hamilton or from the Sierra side. It may be objected that the theory of the greater activity of the streams requires a change of climate. But no change is assumed other than such as would be produced by an elevation of the region.
The submerged valleys of the coast of California figured by Pro- fessor George Davidson in his paper on this subject? show that the coast must have stood much higher when those valleys were cut than it does at present. ‘The reduced charts published by Professor Davidson in his article upon the submerged valleys of the coast show the following minimum elevations required in order that these valleys should again become dry land.
ING aie Sate DiCSOn wwe) ek en MOY ate eapemusoW is, a2 cule MOVE 3 OOOMEeEL iNeatwoantasMionicagen pcs ymcuom Eee eras Gao cae OVET® TD 2OOnI INearaeonteMiuicerereucpees aes Ue coder sans -giietct tims en at se oats cp wee sy GOVETS2;A00W Hasiqoisanacapaislandiy aia esate neuen ge ee Wee abouta- Sool. Sancarecatalinagislandere wane ecm) yet une | ince amen 1S. NOVET Th SOO= Santa @ruz Channel 9 2 3 = TE OVET IT SOOM King Peak submerged valley, south ai Chips Mendocino © ae) OVET 23400) F5 Spanish Flat Valley, south of Cape Mendocino . . . . . over1,800 “ Punta Gorda Valley, south of Cape Mendocino .. . . over3,500 “ Near Capes Viendocinon las We, ems Oe) area ay lite ee OVELL2ACOL 4 Gammel aR aygre y errsaes Moe i ies no taint acomivey) ou smitty Gh in OVET) 31 OOONL INomteTe ye DAVE et or Wyse sec) eerie ea) ou cans over 3,600 “
The dendritic topography of these See ve shown by the hydrographic charts is so characteristic of land forms produced by stream erosions that there seems no escaping the conclusion that they were formed when the region was out of water. There are not always soundings enough to show the topography very far from the shore, and in all cases we seem to have discovered only the upper ends of these submerged valleys.
At the Bay of Monterey, Carmel Bay, and near San Diego, how-
1 Proceedings of the California Academy oj Sciences, 3d ser., ‘“Geology,” Vol. I (1897), PP. 73-103.
8 J. C. BRANNER
ever, the submarine topography is best shown, and at these places there is suggested a former elevation of the land amounting to more than 3,000 feet. In other cases the depths of the dendritic contours are only from 1,200 to 2,000 feet, but in these instances the informa- tion regarding the former edge of the land appears to be imperfect. The absence of a submarine channel off the Golden Gate is probably due tothe fact that the silts from the great valley have completely buried and obscured it.
The separation from the main land of the coast islands, Santa Catalina, Santa Rosa, etc., was produced by a recent depression that left the tops of mountains or hills in the form of islands. This is suggested by the topography of the coast islands, and is borne out by the flora and fauna’ of those islands. The finding of the remains of the mastodon upon the island of Santa Rosa marks? fairly well the period of the former elevation of the coast and of land connec- tion between the present coast and those islands—that is, the separa- tion took place in Pleistocene times.
The peculiarity of the fish faunas of certain streams referred to lies in the fact that in several cases the faunas show that streams which are now clearly separated were formerly connected. In most cases the former connection was apparently made possible by an elevation of the coast which permitted two or three streams to enter the ocean by a single mouth. It is assumed that at such time there was a single fauna in the entire river system. The later depression has submerged the mouth of the stream, and there are now two or three or more separate streams entering the sea through as many mouths, in place of a single system entering the ocean through one mouth.
In the theoretical case suggested by the accompanying figure
t John Van Denburgh, “The Reptiles and Amphibians of the Islands of the Pacific Coast of North America,” Proceedings of the California Academy of Sciences, 3d ser., “ Zodlogy,” Vol. IV, No. 1. The author reports four amphibians, nineteen lizards, and six snakes (twenty-nine in all) on the islands, of which fifteen live on the mainland.
2 Joseph Le Conte, “The Flora of the Coast Islands of California, etc.,” American Geologist, Vol. I (1888), pp. 76-81; Proceedings of the California Academy of Sciences, Vol. V (1873), p. 152; American Journal of Science, 3d ser., Vol. XXXIV (1887), pp. 457-60. L.G. Yates, American Geologist, January, 1890, pp. 51, 52.
DRAINAGE OF THE SANTA CLARA VALLEY 9
it is clear that when the sea came up to the “old shore” line, fish could mingle throughout the entire drainage system represented. A depression that would place the “later shore” line as indicated would cut off the southernmost branch, but would leave the fishes free to move through the other branch of the river system. A depres- sion bringing the water up to the “present shore”? would separate the original single drainage system into five different systems, while the faunas would remain more or less the same as the one that occu- pied the ramifications of the streams when the drainage all entered the sea through a single mouth. It is to be expected that in time the faunas diverge, and that the longer they are separated, the greater
Fic. 2.—Theoretical case to illustrate the effect of coast depression on the fauna of streams that originally belonged to one system, but became separated by submergence.
the difference will be. The Coyote and Pajaro drainages have been separated since the streams ceased to be so active, and it seems quite reasonable to suppose that that period was at the close of the glacial epoch. The ichthyologists state that the fishes in the separate streams are already showing perceptible differences—differences that could only be expected after a long period of separation.
Mention should be made of the finding of marine shells in wells put dowa on the plain northwest of San José. In the Tenth Annual Report of the State Mineralogist of California for 1890, p. 610, Mr. Watt says that “marine organisms have also frequently been met
10 Joe CSB RAUNGINIEDR:
with.” ‘Oyster shells” were obtained in a stratum of bluish sand, and a stratum of blue clay containing numerous “clam shells”’ is said to have been bored through about two miles north of Alviso. The finding of these marine deposits seems to show that the materials in the valley bottom are not of land origin. ‘The deposits referred to might be either preglacial or postglacial without interfering with the theory of the elevation of the coast during the glacial epoch. In every instance, however, these marine shells have been found so near the present Bay of San Francisco that I am disposed to believe that the deposits containing them belong to the late history of the Bay and not to the more remote period.
Résumé.—The theory of the postglacial age of the Golden Gate does not appear tenable. ‘The watershed at Madrone in the Santa Clara Valley between Coyote Creek and Pajaro River is not the lowest one between the Bay of San Francisco and the Pacific; the one at Colma is 155 feet lower, and another in Elk Valley is also 155 feet lower. The mingling of the fish faunas of streams flowing into the Bay of Monterey with those of streams entering the Bay of San Fran- cisco is explained by the fact that Coyote Creek, descending into the Santa Clara Valley from the Mount Hamilton range at the crest of the watershed between the San Francisco Bay and the Bay of Mont- erey, formed an alluvial cone and swung from side to side, emptying part of the time into the Pajaro and part of the time into the Coyote. The passage of fishes between the various streams entering the Bay of San Francisco must have taken place at a time when the coast stood enough higher than it does at present to have emptied the Bay of San Francisco, and thus to have permitted fishes to descend from the Sacramento and ascend the Coyote and other streams without entering salt water. ‘This same elevation would permit the passage of fishes between streams entering the Bay of Monterey.
It is believed that the elevation that united these streams occurred during the glacial epoch, and that it was the larger run-off of waters of that epoch that built up the alluvial cone where the Coyote debouches on the flat floor of the Santa Clara Valley.
ON THE PROBABLE GLACIAL ORIGIN OF CERTAIN FOLDED SLATES IN SOUTHERN ALASKA
ELIOT BLACKWELDER University of Wisconsin
In the mountains east of Yakutat Bay, on the southeast coast of Alaska, a bowlder-shale terrane of unusual character has been noted by Tarr,' and was observed by the writer with some minuteness last summer. ‘There is reason to believe that glaciers were instru- mental in the formation of this deposit. If the supposition is correct a certain novelty attaches to the occurrence because the formation is not only old but is highly folded and slightly metamorphosed.
The rocks are well exposed in the canyons of Moser? and Miller Creeks and in the high bench west of them. A terrane, which is apparently the same, is that reported by Tarr from the shores of Russell Fiord.
The strata in question are several hundred feet thick and constitute a member of the Yakutat series. Typically they are conglomeratic shales, or slates, according as secondary cleavage has been developed or has not. The body of the rock is a black or dark-gray shale of relatively gritty and heterogeneous composition. In many places the matrix is definitely stratified, but elsewhere this structure is obscure or not visible.
The pebbles and bowlders in the conglomerate are the features of chief interest. Lithologically they include a large variety of rocks, some of which are known to occur not far away, while the source of others is unknown. Among them are such varieties as greenstone, gray limestone, granite, quartzite, graywacke, black slate, and flint. In size the bodies range from pebbles to bowlders of large dimensions. At least two which were more than fifty feet in length were seen imbedded in the shale, while blocks five to ten
t He mentions shale-conglomerate as a member of the Yakutat series. Bulletin, No. 284 (1906), p. 62, U. S. Geol. Surv.
2 See map in Bull., No. XXI, U.S. Fish Com.
it J
I2 ELIOT BLACKWELDER
feet in diameter are common. These pebbles and bowlders are not sorted or arranged in any way whatever. Large and small are inti-
mately mingled and are not deposited in layers as in ordinary current- laid conglomerates. The long diameters of the bowlders are not more often parallel to the stratification than oblique to it. The shape of the pebbles and bowlders is significant, since waterworn forms were seldom observed and sharply angular bodies are even less com-
Fic. 1.—Glaciated exposure of bowlder shale in the Yakutat series. The largest bowlder is about 6 feet in diameter. mon. The great majority of the bowlders have rounded corners and edges, but are otherwise rather irregular.
The beds of conglomerate appear to form the lower part of the Yakutat series, but the base on which they rest has not been found. Above, they seem to grade into stratified shales which are devoid of pebbles, and these in turn are followed by alternate dark shales and graywackes. ‘The entire series has been intensely folded and broken by numerous faults. Locally, the deformation has been sufficiently
ORIGIN OF CERTAIN FOLDED SLATES IN ALASKA 13
severe to distort pebbles in the conglomerate and to develop secondary cleavage in the shales. A number of the pebbles and small bowlders were dug out of the matrix, and carefully examined for surface mark- ings, such as glacial striae, but without success. ‘The shale usually adheres more or less closely to the pebbles imbedded in it, as if it had been actually welded to their surfaces. On this account no favorable exteriors were obtained.
The age of the formation is not yet definitely known. The Yak- utat series has been assigned to the Jurassic by Ulrich, on the basis of fossils found in rocks near Kodiak which are thought to be the same age; but Wright? is inclined to regard it as somewhat older—probably late Carboniferous.
The interpretation of the shale conglomerate is beset with some difficulties arising from insufficient data, but the facts at hand seem, nevertheless, to indicate that the deposits are of glacial origin. The lack of striations on the bowlders is believed to be largely due to subsequent deformation which has defaced or obscured the original surfaces on which such markings may have been made. ‘The large size and the variations in both size and composition among the bowlders seem incompatible with the hypothesis that the beds have been formed entirely by aqueous currents. The subangular yet irregular shapes of the bodies are also more suggestive of glacial origin than of any other. ‘There is one feature of the formation which is sufficient, however, to prove that even if glacial it is not an ancient deposit of till or moraine, namely, the distinct stratification. ‘The shale matrix was evidently accumulated in quiet waters where condi- tions favored the settling of clays and silts in successive horizontal layers. A suggestive condition now prevails in this very region: in the broad estuary called Yakutat Bay, fine sediments are doubtless now accumulating; at the same time abundant icebergs drift out from the glaciers at the head of the bay and eventually melt before they reach the Pacific. Obviously the bowlders and finer débris enclosed in this floating ice are strewn over the bottom of the bay, and it may be supposed that the result is a stratified argillaceous
tE. O. Uhlrich, Harriman Alaska Expedition (1904), Vol. IV. 2C. W. Wright, in conversation with the writer at the close of the field season of 1906.
14 ELIOT BLACKWELDER
formation containing in random arrangement an abundance of bowl- ders and smaller fragments of rocks of various sizes, shapes, and com- positions. It seems probable that the shale conglomerate of the Yakutat series had a similar origin—that it is in fact a marine shale enclosing the contributions of icebergs derived from local glaciers of late Paleozoic or early Mesozoic age.
NOTES ON GLACIATION IN THE SANGRE DE CRISTO RANGE, COLORADO’
C. E. SIEBENTHAL
In connection with an examination of the artesian basin of the San Luis Valley, Colorado, In 1903, several opportunities were had to make observations in the Sangre de Cristo Mountains, and various notes on the glaciation of that range are here recorded.
Attention has heretofore been called to glaciation on the eastern slope of these mountains by J. J. Stevenson,” who describes and figures the well-developed Grape Creek moraine, about midway of the range north and south. F. M. Endlich? also alludes to small indications, of glaciation, so uncertain in their character that he prefers to disregard them altogether. As a matter of fact, not only has the range suffered general glaciation, but even at present contains two living glaciers.
No pretense is made to completeness, individually or collectively, for the following notes. ‘The observations were for the most part confined to the western side of the range. The sharp precipitous western slope merges into the great alluvial slope which skirts the western base of the range. Each stream valley which heads against the crest-line has its valley trains of glacial débris, which ordinarily reach down to and, at an elevation of about g,o0o to 9,500 feet above tide, crown the alluvial cones making up the alluvial slope.
The northernmost glaciation observed is in Black Canyon, just east of Orient Station on the Denver & Rio Grande Railway. Here are lateral moraines on each side of the creek 100-200 feet in height, and reaching nearly or quite to the lower end of the canyon.
The next canyon to the south in which morainic deposits came to the notice of the writer is Willow Creek, east of the village of Crestone.
1 Published by permission of the Director of the United States Geological Survey.
2U. S. Geographical and Geological Survey West of the tooth Meridian, Vol. III (1875), PP- 434) 435-
3 U. S. Geological and Geographical Survey of the Territories, Annual Report, 1875, p. 220.
15
C. E. SIEBENT HAL
16
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GLACIATION IN SANGRE DE CRISTO RANGE 17
The view looking up this creek (Fig. 1) shows Willow Creek Park in the immediate foreground. This is a natural meadow, 80 or 100 acres in extent, formed by the draining of a glacial lake. Two existing lakes are found in Willow Creek Valley above the park—one a beauti- ful, clear, deep pool half-way between the Park and the summit, and the other a smaller one in the cirque at the head of the creek. Polished surfaces, striae, and other evidences of glaciation are common all along the valley.
The next moraine visited was that of South Zapata Creek, the northernmost of the circle of radial streams which head in the Blanca massif. ‘This moraine, as seen in the distance, just crowns the crest of the great alluvial fan which Zapata Creek has built. ‘The foot of the moraine has an elevation of about 9,000 feet, and is 1,400 feet above the level of the valley at the foot of the fan in the vicinity of Za- pata ranch house. ‘There are two concentric moraines, the outer one about 50 feet the higher. The front of the outer moraine is about 350 feet in height. Both are covered with large bowlders. The inner one formerly inclosed a small lake, the outlet of which cut through the moraine where it adjoined the canyon wall on the north side and, once incised in the rock, has continued to cut back a narrow winding cleft, sometimes not more than two or three feet wide, down through which the water pours, forming the picturesque Zapata Falls. A lake also exists near the head of the creek.
Middle Creek, the next stream to the south, exhibits a similar crescentic moraine crowning the great spreading alluvial fan over which large bowlders are scattered from crest to base.
Bear Creek heads against the crest of the range just north of Blanca Peak. ‘There is a very small lake in the cirque at the head of the creek, two or three small ponds down the creek some distance, and a fine little lake about 2,500 feet below the summit in altitude. There is little morainic material to be seen in the valley above the elevation of 10,000 feet. The valley is rounded and glaciated up the sides to the overhanging cliffs, but in places the glaciated portion is covered by “‘slide rock”’ or talus from the cliff. A light fall of snow will hang on the unglaciated slope and on the talus, but not on the cliffs, and after such snows the height to which the ice occupied the various creek valleys can be plainly seen from the center of San Luis Valley. At
18 C. E. SIEBENTHAL
10,000 feet elevation the trail up the creek crosses over the upper mo- raine on the south side, and the view shown (Fig.2) is from this point. There are here inner and outer moraines, the latter 125-150 feet the higher. The inner moraine extends the farther out on the fan, differ- ing in this respect from the Zapata moraines. The height of the moraine from its foot on the fan to the top of the outer ridge is approxi- mately 500 feet. | Landslides in the moraine show its constitution to be true glacial débris.
The various streams descending the south slope of Sierra Blanca likewise held their appropriate glaciers. The moraine in Little Bear
Fic. 2.—Moraines on north side of Bear Creek. Inner moraine forms a bench covered with a growth of pines.
Creek reaches barely to the mouth of the canyon at the apex of the fan. Blanca Creek has a pronounced moraine, extending beyond the mouth of the canyon and down the slope of the fan, the older, outer moraine reaching the farther, and the inner one being the higher. The two branches of Ute Creek both exhibit moraines and glaciated contours, and contain several lakes in their upper courses. ‘The various streams which head in the Blanca massif number in their valleys some thirty lakelets, large and small.
The valley of the Huerfano, heading on the northeast side of Blanca Peak, is distinguished from the others by the presence of living glaciers—small, it is true, but characteristic. The valley of the Huerfano, up to the base of the steep north side of Blanca peak,
GLACIATION IN SANGRE DE CRISTO RANGE 19
is a U-shaped valley with meadows and grassy patches, the lower slopes well rounded and glaciated. The lower limit of glaciation is beyond the region of the writer’s observations.
On the north side of the valley, at the junction of the granite and the quartz conglomerate, a small valley has been cut out, and in this has formed the very pretty example of talus glacier shown (Fig. 3.). This mass of débris is about a third of a mile long and about 150
Fic. 3.—Talus glacier in small valley entering Huerfano Valley from the north, three miles north of Blanca Peak.
feet high at its lower termination. In the valley below several morainic trains may be seen emerging from beneath the talus glacier, showing that true glaciation preceded the formation of the talus glacier, which, from its bareness of vegetation and steep slopes, seems to be relatively recent in age. Streams of rocky material can be seen descending on to the débris, which has a remarkably smooth outline to have been formed through the agency of avalanches alone. Intermingled snow and ice must have played an important part in its formation.
20 C. E. SIEBENTHAL
The Blanca glaciers lie snugly under the steep north face of Blanca Peak as will be seen in Fig. 4, taken from a point about a half-mile north of McMillan’s mine, which appears in the foreground. The glacier on the left, mostly covered with fresh snow, is the smaller. The surface of this glacier shows many small longitudinal gullies and another system running transversely. These seem to be largely due to
Fic. 4.—Blanca glaciers from the northeast.
original wind ripple-marks in the snow into which dust has settled, melting them deeper.
The north glacier, the one on the right, is shown in a nearer view (Fig. 5), taken from the moraine immediately below it with the camera tilted upward somewhat. Figure 6 is a view northward across the same glacier from a point near the southern one. ‘These two views display the glacier very well. The width of the glacier is about 800 feet, and its greatest length is about 1,000 feet, although the ice probably extends a considerable distance farther beneath the terminal moraine. The glacier lies in a pocket on the mountain side, and the ice is prob-
+
GLACIATION IN SANGRE DE CRISTO RANGE AAT
ably quite thick. A prospecting tunnel, starting in the moraine below the edge of the visible ice, went horizontally in the clear ice
Fic. 6.—Blanca glacier, looking north.
for a distance of 115 feet without reaching rock, which, taking into account the slope of the surface, demonstrates a vertical thickness of
22 CoE. SLE BENGIREVAL
over 80 feet. ‘The slope of the ice surface is very steep, about 42°— quite too steep for climbing without alpinestock and_ice-creepers. Two embryonic terminal morainic ridges are visible, the lower and larger one some 400 feet below the present edge of visible ice. The ice, as will be noted, shows the characteristic upturned dirt bands looped concentrically about the point of supply, and the surface of the lower half of the glacier is for the most part covered with fine black gravelly dirt, residual from the dirt bands. Many small longitu- dinal rivulets have cut gullies down the otherwise notably smooth surface of the ice, exposing the banded ice beneath the dirt covering. The ice itself displays characteristic gletscherkérne about one-tenth inch in diameter. Because of the conformation of the pocket in which the ice accumulates, the production of crevasses is impossible, with the exception of a definite bergschrunde which marks the line where the upper edge of the ice pulls away from the rock wall in the wasting season. The precipice above and the steep face of the glacier cause loose fragments falling upon the ice to attain great velocity in their passage across if, so that examination of the glacier is attended by considerable danger from these flying rocks.
The Blanca glaciers possess an added interest in being the southern- most existing glaciers yet reported in the Rocky Mountains, and, so far as known to the writer, the southernmost in the United States, Their latitude is 37° 35’ N., their longitude 105° 28’ W., and their elevation about 12,000 feet.
Summary.—The various stream valleys heading against the crest of the Sangre de Cristo Range held Pleistocene glaciers, the morainic remains of which fall into two systems, showing the existence of two periods of glaciation. The moraines of both systems are com- paratively fresh-looking, and the outer, older ones are not noticeably more eroded than, or different topographically from, the inner, later ones. The inner moraines are sometimes lower, sometimes higher, than the outer ones, and while they usually are shorter than the older moraines, sometimes, as in Bear Creek valley, they transgress the older moraine and extend farther out upon the alluvial slope, these irregularities being due presumably to variable local conditions in Pleistocene time.
THE PLACE OF ORIGIN OF THE MOON—THE VOL- CANIC PROBLEM
WILLIAM H. PICKERING
In 1879 Professor George H. Darwin propounded the view that the Moon formerly formed a part of the Earth. That it was origi- nally much nearer to the Earth than it is at present, and is now slowly receding from us, was clearly shown by his equations. After considerable discussion, his conclusions have been accepted by the great majority of astronomers, although many of the geologists do not view them with favor. Assuming the correctness of his hypoth- esis, it will be of interest to determine, first, if possible, from what part of the Earth the Moon originated, and, second, to follow out our conclusions on this point and see to what results they may lead.
_ When the separation took place, it has been shown that the com- bined planet was not very much larger than is the Earth at present. It must therefore have been mostly in the solid or liquid condition. If in the latter state, it is obvious that no indication of the Moon’s former place could be found at the present time. Very few astron- omers or geologists today, however, believe that the Earth ever was completely liquid. It has probably always been partly solid, partly liquid, and partly gaseous. It is composed of such diverse materials, and these are exposed at different points throughout its volume to such diverse pressures, that, unless we assume it to have condensed from a highly ineandescent nebula, which is unlikely, we should scarcely expect it ever to have presented a uniform liquid surface.
The surface was probably hot, but how hot we have no means of knowing. Beneath the surface, however, where radiation was impossible, much higher temperatures were found, as is still the case and in what follows we shall assume that the interior was practically liquid, or was ready to become actually so where relieved of the pressure due to the gravity of the outer layers; that is, where the centrifugal force became sufficiently high, as in the equatorial regions. Precisely how the Earth came into its present form, whether by
23
24 WILLIAM H. PICKERING
planetesimal condensation or otherwise, does not concern us here. We merely assume that in these early days the Earth was in much the same condition that we find it at present, except that it was hotter. We also assume that it was slowly condensing from a more bulky form, rendering fission possible.
These processes of fission and condensation we see going on all around us at the present time in the stellar universe, as indicated by the variable stars of short period and the spectroscopic binaries. It therefore requires no great stretch of the imagination to conceive that it may also have occurred on a smaller scale in the case of our Earth and Moon.
It does not follow, however, that our combined planet was ever incandescent. Indeed, this seems to be unlikely. A cold nebula which is later to condense into a sun must almost necessarily be com- posed largely of solid matter. The electric disturbances by which we see it, illumine only the gaseous portions, but the metallic elements must be there nevertheless, all the time unseen.
Assuming then a hot, solid, ellipsoidal Earth, with an interior more or less liquid, at least beneath the Equator, revolving on its ‘axis once in about four or five hours, we have a picture of our as yet moonless planet as conceived by the astronomer. As it continued to cool, vast volumes of steam and other gases escaped from its interior, increasing its density and diminishing its volume.
As its volume diminished, its speed of rotation increased, until by centrifugal force, as explained by Darwin, the Moon was born. If the crust was solid, and if the Moon escaped from it, it is almost certain that a scar of some sort would have been left, and it is of interest to see if we can find it.
The specific gravity of the Earth as a whole is 5.6. That of the surface material ranges in general between 2.2 and 3.2, with an average of 2.7. Ihe specific gravity of the Moon is 3.4. his indicates clearly that the Moon is composed of material scraped off from the outer surface of the Earth, rather than of matter obtained from a considerable depth. At the same time, the specific gravity 3.4 indicates that the layer of material removed had an appreciable thickness.
As is well known, the land and water are very irregularly dis-
PLACE OF ORIGIN OF THE MOON ANS
tributed over the surface of our globe. If we erect a perpendicular from a point situated one thousand miles to the northeast of New Zealand and view the Earth from a distance in this direction, we shall find that very little land will be visible, while the outline of the Pacific will approach the form of a circle.
BIG
Figure 1 is a map of the globe on zenithal projection, where the radii are proportional to the actual distances represented. ‘There 1s no distortion, therefore, in the radial direction, and the exact shape of the Pacific with regard to a great circle is clearly shown. The inner circle represents the circumference of the globe, and is there-
26 WILLIAM H. PICKERING
fore go° from the central point. The latitude of this point is 25° S. Away from the center the tangential distances necessarily become more and more distorted, the distortion at the circumference making
them appear = , or 1.6 times too large.
: CONTINENTAL \ PLATEAU
OCEANIC PLATEAU
Figure 2 is taken from Gilbert’s Continental Problems of Geology (Smithsonian Report, 1892), p. 164, and is founded on the results of the Challenger Expedition as deduced by Murray. In it ordinates represent feet, and abscissas areas, the extreme abscissa representing the total area of the Earth’s surface. This area is composed chiefly of two plateaus: one the continental, whose mean altitude is 1,000 © feet above sea-level; the other the oceanic, whose mean altitude is = 14,000 feet.
It will be noticed that the edge of the continental plateau is below sea-level, but not more than 1,000 feet below it. This contour may be taken, therefore, as the true boundary more properly than the water-line itself. In Fig. 1 it is indicated by a dotted line. Its position near the Antarctic continent is unknown. The location of the latter, excepting where indicated by the full line, has not been determined. The line composed of dashes therefore indicates its maximum possible area. :
If we travel north go° from the central point of Fig. 1, to the immediate vicinity of Bering Strait, and erect another perpendicular, from which we again examine the globe, we shall obtain a view resem-
PLACE OF ORIGIN OF THE MOON 27
bling Fig. 3. In this map, which is drawn in orthographic projection, there is no tangential distortion, and the appearance is that which the Earth would have if seen from a great distance. The vertical line is a meridian; the horizontal is a projection of the inner circle shown in Fig. 1. The continents and islands at the edges of the disk have
Fic. 3 been allowed to project out beyond the ocean beds in order to make more evident the systematic grouping of the continental masses on one side of the globe. With the exception of Australia, the Antarctic continent, and a small part of South America, all represented in the lower half of Fig. 1, there is no important land on the water side of the globe, not shown in Fig. 3.
28 WILLIAM H. PICKERING
An inspection of this figure shows that the Earth’s center of grav- ity, which is the center of the circular arcs, does not coincide with its center of volume, and this deviation would be still more marked were the mobile portions of the surface—i. e., the oceans—drawn off. ‘The center of gravity would then be slightly raised in the figure, and the center of volume still more so. The ocean side of the solid Earth has obviously a higher specific gravity than the continental side.
It is the general opinion among geologists that the continental forms have always existed—that they are indestructible. How, then, could they have originated ? We know something of the permanent surface features of three bodies in the universe besides the Earth; namely, the Moon, Mars, and Mercury. None of these shows us anything resembling the irregular terrestrial distribution of the high-and low-level plains, of our continents and oceans.
If we examine more minutely the coasts of our great oceans, we shall find the Pacific bounded by a nearly continuous line of active or extinct. volcanoes, and this is true whether in North or South America, Asia, the East Indies, New Zealand, or Antarctica. The only possible break is the east coast of Australia, but even here there is a line of volcanic islands, lying a short distance off the coast, stretching from New Guinea more than half-way to New Zealand. The coasts of the Pacific are generally mountainous and abrupt, and composed of curves convex toward the ocean.
The Atlantic coasts, on the other hand, are generally low, flat, and composed of curves as often concave as convex. As to vol- canoes, they are few and scattering. The only conspicuous exception to the general rule is the range of the Lesser Antilles, which both in form and volcanic nature reminds us of the Pacific coast of Asia. The Indian Ocean resembles the Atlantic, except where it approaches the vicinity of the Pacific, and there the characteristic volcanoes again appear.
A curious feature of the Atlantic Ocean is that the two sides have in places a strong similarity. Figure 4 is drawn in globular projection, which is used so frequently for the hemispheres in ordinary atlases, except that in this instance the projection is carried over the Pole onto the other side. This projection gives very little distortion
PLACE OF ORIGIN OF THE MOON
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30 WILLIAM H. PICKERING
in the vicinity of the central meridian, which is the portion of the map to which we shall especially refer. ‘The shaded areas represent those parts of the ocean that are more than 1,000 feet in depth. Regarding the unshaded area between America and Asia we have no information.
When the Earth-Moon planet condensed from the original nebula, its denser materials collected at the lower levels, while the lighter ones were distributed with considerable uniformity over its surface. At the present day we find the lighter materials missing from one hemisphere. ‘The mean surface density of the continents is about 2.7. ‘Their mean density is certainly greater. We find a large mass of material now up in the sky, which it is generally believed by astron- omers formerly formed part of our Earth, and the density of this material, after some compression by its own gravity, we find to be 3.4, or not far from that of the missing continents. From this we conclude that this mass of material formerly covered that part of the Earth where the continents are lacking, and which is now occupied by the Pacific Ocean. In fact, there is no other place from which it could have come.
Who it was that first suggested that the Moon originated in the Pacific is unknown. The idea seems to be a very old one. The object of the present paper is to find what support for this hypothesis is afforded by the results of modern science, when examined both qualitatively and quantitatively.
The volume of the Moon is equivalent to a solid whose surface is equal to that of all our terrestrial oceans, and whose depth is thirty- six miles. It seems probable, therefore, that at this time the Earth had a solid crust averaging thirty-six miles in thickness, beneath which the temperature was so high that the materials were in places liquid, and in other places only kept solid by the enormous pressure of the superincumbent material. When the Moon separated from us, three-quarters of this crust was carried away, and it is suggested that the remainder was torn in two to form the eastern and western continents. These then floated on the liquid surface like two large ice-floes.
If their specific gravity was the same as that of the Moon, 3.4, since the continental plateau averages nearly three miles higher
PLACE OF ORIGIN OF THE MOON BT
than the ocean bed, the specific gravity of the liquid in which they floated must have been 3.7. Later, when this liquid surface cooled, the huge depression thus formed was occupied by our present oceans.
The volcanic islands in the oceans, such as Hawaii, were obviously formed after the withdrawal of the Moon, and are analogous to the small craters scattered over the lunar maria. While their surface material presents no extraordinary density, the lava being full of bubbles and small cavities, interesting results have been obtained by the Coast Survey with the pendulum. Observations were made by E. D. Preston near the summit, and on the slopes of Mauna Kea, Hawaii, at altitudes of 13,060, 6,660, and 8 feet. He writes:
It appears that the lower half of Mauna Kea is of a very much greater density than the upper. The former gives a value of 3.7 and the latter 2.1, the mean density of the whole mountain being 2.9. ‘This is somewhat greater than that found for Haleakala [a neighboring volcano] and is notably larger than the density of the surface rocks. Indeed, this appears to be the highest value yet deduced from pendulum work.
The remark of Major Dutton? is interesting in this connection, that a part of the bulk of these mountains is due to accumulation, and a part to uplifting. The upper half is clearly due to matter, chiefly scoria, which has been expelled from the various vents. ‘The lower half is probably due to the slow uplifting of the former ocean bed.
It would seem as if borings carried on in this vicinity to a depth of only a few hundred feet would bring to the surface the same kind of rock material that, beneath the continents, would only be found at a depth of many miles. Presumably this material would turn out to be lava similar to that found on the surface, save that under the great pressure the innumerable little cavities, rendering the material generally so porous, would have practically disappeared. The fact that its density, 3.7, as determined by Preston, coincides with the theoretical value just deduced is of interest.
Turning now to Fig. 4, six points indicated by circles have been marked along the coast-line of the eastern continent. Correspond- ing to these, six similar points have been marked along the American
1 American Journal of Science, Vol. CXLV (1893), p. 256. 2U. S. Geological Report, 1882-83, p. 195.
32 WILLIAM H. PICKERING
coast. ‘The two broken lines joining these various points are slightly inclined to one another, but the other small differences in relative position and distance are apparent and not real, being due to the necessary slight distortion of the map. The South American con- tinent does not fit well into this arrangement, and does not appear to have remained perfectly parallel to North America during its transit across the fiery ocean, in obedience to the pull of the Moon. Instead, it seems to have rotated slightly, as shown, about a point somewhat to the east of the Isthmus of Panama.
In trying thus to match the continents together, we must take the outline of the continental plateau rather than the coast-line. Five- sixths of the area of the Altantic basin is thus very well accounted for, but there still remains a considerable area east of the United States, together with the Gulf of Mexico, and the Caribbean and Medi- terranean Seas, not explained. The eastern outline of the Atlantic area is indicated by the dotted line.
The antipodes of the central spot in the map of the Pacific is indicated by the cross in northern Africa. If the ultimate releasing force which caused the disruption of the Moon was, as has been supposed, the solar tides, we should expect that a certain amount of material might escape from both sides of the Earth. If the Sun were overhead at the central point in the Pacific, then within less than an hour, using Darwin’s rate of rotation, it would have been exactly opposite to the area in question in the Atlantic, Gulf, and Caribbean Sea.
The similarity of the Lesser Antilles to the Asiatic islands, already pointed out, corroborates this explanation. It is also to be noted that the greatest depths in the Atlantic, 21,000 feet, are found along the eastern boundary of this region. Similarly, one of the deepest parts of the Pacific, 31,000 feet, is indicated by the X close to the central point on the map, Fig. 1. Around this deep portion on the east, north, and west is a shallower area from 15,000 to 20,000 feet in depth, and then, as we approach the continents, again a deeper area.
All those who have studied the stratification of the Appalachian region have concluded that the sediments came chiefly from the east. Such extensive deposits require a larger land area than now exists;
PLACE OF ORIGIN OF THE MOON 33
in fact, one is needed of continental proportions. Whether these deposits are sufficiently ancient to be explained by the lunar hypoth- esis the writer is not prepared to say.
There are several coincidences relating to the position of the central point of the Pacific which may or may not be accidental. The close coincidence with the very deep area above noted is the first of these. The second relates to its latitude, -25°. This is within a degree and a half of the tropic of Capricorn. ‘The tropics are the lines on a uniform sphere where the direct solar tidal pull acts for the greatest length of time on any particular area of rock. Here also the leverage of the tidal pull on the Earth’s crust would be greatest in displacing a protuberant equatorial ring. If the Moon were generated from the Earth by centrifugal force, liberated by the tides, we should expect the central point to coincide with one of the tropics of that time. The coincidence with the present tropic would indicate that the axis of the Earth can have changed very little in the meantime. The third and fourth coincidences are more likely to be accidental. The third is that the central point coincides in longitude with Bering Strait, where the two continents are supposed to have slipped past one another. The fourth is that the strait is almost exactly go°, more accurately g1°, in latitude from the central point.
If the greater continents were split apart, we should by the same analogy conclude that Antarctica and Australia were drawn from the Indian Ocean; the former from the vicinity of the Cape of Good Hope, the latter farther east.
If it is true, as here suggested, that we owe our continents to the Moon, then the human race owes far more to that body than we have ever before placed to its credit. If the Moon had not been formed, or if it had carried away the whole of the terrestrial crust, our Earth would have been completely enveloped by its oceans, as is presumably the case with Venus at present, and our race could hardly have advanced much beyond the intelligence of the present deep sea fish. If the Moon had been of but half its present bulk or had been slightly larger than it is at present, our continents would have been greatly diminished in area, and our numbers decimated, or our lands overpopulated.
34 WILLIAM H. PICKERING
Connected intimately with the origin of the continents is the problem as to the cause of volcanoes, and why they are at present always situated near the sea. A point that is of the utmost conse- quence in its bearing on this question is the fact, noted by Charles Darwin, that active volcanoes are found only where the coast-line is rising. Clearly the same cause produces both effects.
A rising region, as pointed out by Dutton, must evidently be increasing its volume. This increase may occur either with or without an increase of mass. In the latter case the increase must be due toarise of temperature. It has been shown that, if a part of the Earth’s crust fifty miles in thickness were to have its temperature raised 200° F., its surface would be raised to the extent of 1,000 to 1,500 feet.‘ The Bolivian plateau has an elevation of two and a half miles. That of the Himalayas is about a mile higher. It is improbable that these elevations are due to this cause.
The alternative is that in the rising regions we have an increase of mass. If the mass were increased materially, it has been shown by Gilbert? that the hot subterranean region should yield to the added pressure, thus neutralizing the elevation. An added column of rock two miles in height could not possibly be supported. Appar- ently our last resort is to introduce some lighter material, such as water or steam. ‘The pressure on the steam, if its temperature were above the critical point, would be so great that its density would be but little less than the equivalent extrapolated value for water. It might have one-fourth of the weight of an equal column of rock.
Liquid lava is full of water, and as the lava cools the water is expelled from it. The lava at Hilo, Hawaii, contains innumerable bubbles, indicating the presence of steam, which had been retained by it within its structure for many days, ever since it had left the crater of Mauna Loa, fifty miles distant.
Since volcanoes are intermittent in action, the charging process must still be going on at the present time; otherwise there would have been one long discharge in the distant past, which would have ren- dered all our present volcanoes extinct.
Since volcanoes are active only near the oceans, it has been sug-
t Judd, Volcanoes, p. 347.
2 Continental Problems of Geology, Smithsonian Report, 1892, p. 165.
PLACE OF ORIGIN OF THE MOON 35
gested that the eruption is due to sea water that has entered by cracks in the Earth’s crust and is subsequently discharged from the volcano. Volcanoes do discharge salt water, but the solid ingre- dients of the water do not occur in the same proportions that they do in the sea. Some of the sea salts are often found to be absent, while other salts are often found that do not occur at all in sea water. This fact, together with the inherent improbability that sea water should be sucked in at a low level and pumped out at a high one, renders this explanation improbable.
Another explanation of the universal presence of water in vol- canic products is that it is derived from rain water, which has per- colated down through the soil. This theory, however, does not account for the fact that volcanoes are always found near the sea. Neither of these theories account for the gradual elevation of the land in volcanic regions.
Since the process of charging volcanoes with steam is still going on, and since it appears that the necessary water is not derived from either the sea or the atmosphere, the only alternative seems to be that it comes from the heavy stony material forming the ocean beds, and does not come in appreciable quantities, at present, from the lighter material forming the continents. It is evident, however, that this lighter material is sometimes cracked, permitting the discharge to take place through it. This was the case with the extinct volcanoes in central Europe, and those near the Yellowstone Park and Arizona in this country. The volcanoes at present active in North and South America seem to rise from what was probably formerly the edge of the continental plateau. |
The next question that arises is: From what depth does the lava come? Judged by its temperature at the vent, unless it becomes heated by friction, by compression, or by radio-activity, on its way to the surface, which seems improbable, it must have come from a considerable distance. The rate of increase of temperature with the depth varies in different parts of the world from 20 to too feet per degree Fahrenheit. It may fairly be taken near the surface at too° per mile of depth. From its surface temperature, Bonney estimates? that ‘‘the lava is generally supplied from a zone situated
t Volcanoes, p. 284. :
36 WILLIAM H. PICKERING
at a depth of from 20 to 25, or possibly to 30 miles, in the crust of the Earth.”’ The total thickness of the crust has been estimated by Fisher’ at 30 miles. These values agree very well with that just computed from the volume of the Moon.
Daubrée has shown? that water separated from a chamber filled with steam at a temperature of about 160°C. by a close, fine- grained sandstone, passed through the slab with ease, against the outward pressure of the steam. He also found that the facility with which the water found a passage was increased by heat. There is therefore no difficulty in understanding the transmission of water through hot rocks at considerable depths. Its presence, moreover, would tend to lower the melting-point of the rock, and make it more VISCOUS.
A certain amount of water may even be transmitted in this manner down through the ocean floors; but when we consider that the transmitting medium consists of cold rock several miles in thickness, the water advancing against a constantly increasing pressure, it does not seem that the amount transmitted per year in this manner can be very large.
In our hypothesis explaining the origin of the continents, it was stated that they were composed of the crust which was either originally solid or else had already cooled sufficiently to become so. They had therefore expelled a large part of any water which they may originally have contained. The ocean beds at the time of the great catastrophe were liquid. They therefore absorbed all the water available, if indeed they were not already saturated with it. They had a much higher temperature, having come from a greater depth, and contained much more water at this period, than the continents, and, it is believed, have been giving it out as they cooled ever since.
Doubtless the hot bases of the continents have absorbed some water from the ocean beds as the latter cooled, and the expansion and diminished, specific gravity thus caused would tend to elevate them in the vicinity of the oceans. This has occurred notably in the vicinity of the Pacific, the whole of whose coasts are at the present time in a state of elevation. We can understand also that the sys-
t Milne, Sezsmology, p. 120.
t Geological Experiments, Vol. I, p. 237.
PLACE OF ORIGIN OF THE MOON 37
tematic difference in material and density, extending over large areas, would render the boundaries of the continents more subject to cracks, with their resulting volcanoes and earthquakes, than other portions of the Earth’s surface. A zone of territory subject to earthquakes extends around the Pacific.
As is known from its rigidity, the interior of the Earth as a whole is solid. There cannot even be at present a continuous liquid sur- face between the center and the crust. Beneath every active volcano, however, there must be an area from which its lava is derived. In some way, without doubt by the contraction of the Earth, this lava is caused to approach the surface, and on the way it gradually changes from a viscous solid to a viscous liquid. There are only two ways in which this change can take place: one is by an increase in tem- perature, the other by a decrease in pressure. The latter is probably the actual one.
Tangentially considered, the lower portions of what we may for convenience call the Earth’s crust are in a state of compression, the upper portions in a state of tension. Radially all are in a state of compression. Between the upper and lower portions is a neutral sur- face of no tangential strain. When a crack caused by the tangential tension reaches this neutral surface, the viscous rock oozes up through it, becoming more and more liquid as it approaches the surface and the pressure is diminished. As it melts and is relieved of pressure, its density diminishes, and, if it finally reaches the surface, the erupted lava will continue to flow till the pressure at its source is reduced to equality with the hydrostatic pressure at the base of the crack. The larger the opening and the shorter the distance from the surface, the sooner will this equality of pressure occur, and the shorter be the duration of the eruption. The expansion of the bubbles of steam near the top of the crack diminishes the hydrostatic pressure, and their escape obviously causes the explosions usually noticed. The violent manifestations are therefore all generated near the surface, as is the case of a geyser.
The uprush and escape of all this material broaden the crack into a tube several hundred feet in diameter. After the lava has ceased to flow, the steam working its way up to the vent still keeps a somewhat narrowed passage open. It thus continues as a line of
38 WILLIAM H. PICKERING
weakness; and when the flow of steam and viscous rock from below on all sides toward the area of diminished pressure again increases this pressure beyond the breaking strength of the resisting material, the eruption will be renewed.
Volcanoes frequently lie along arcs of circles, which, if complete, would resemble the lunar maria both in size and shape. One of the most complete of these series of arcs has the China Sea for its center, while the volcanoes are found in the Philippines, Celebes, Java, Sumatra, the Malay peninsula, and southern China to the west of Canton. The diameter of this circle is 2,000 miles. The Japan and Bering Seas are similarly partly surrounded by incom- plete arcs. The shape of the latter is decidedly elliptical.
THE DOUBLE CREST OF SECOND WATCHUNG MOUNTAIN.*
J. VOLNEY LEWIS Rutgers College, New Brunswick, N. J.
Twenty miles west of the Palisades of the Hudson River rise the prominent ridges of the Watchung Mountains, which extend south- westward from a point ten miles north of Paterson, N. J., almost to Somerville, a distance of forty miles. The parallel ridges of these mountains are the outcropping edges of extrusive trap sheets imbedded in a series of red shales and sandstones which constitute the upper (Brunswick) member of the Newark system in New Jersey. In general these strata have an average northwesterly dip of 12 tors degrees. It has long been known, however, that the recurved ends of the Watch- ung Mountains swing around the extremities of the boat shaped Passaic Basin syncline, which has been cut off on the northwest by a fault along the border of the crystalline rocks of the Highlands.
The hook-shaped southwestern portion of Second Mountain (see maps, Figs. 1 and 2) is much broader than elsewhere and for a distance of seventeen miles the crest is distinctly double. This condition has been explained? as the result of a curved longitudinal fault parallel to the present outcrop of the trap sheet. While entirely consistent with the facts, so far as at present known, the probability of such a coinci- dence is so extremely small that, in the absence of positive proof of faulting, this hypothesis must be regarded as exceedingly doubtful,
It is the object of the present paper to explain the observed con- ditions upon an altogether different basis, and in a manner requirmg no assumptions that are in any way improbable in the light of our present understanding of the geologic history of the region. For this purpose brief discussions are here given of (1) the facts requiring explanation, (2) the interbedded shale hypothesis, (3) the curved longitudinal fault hypothesis, (4) the hypothesis of double flow with
« Published by permission of the State Geologist of New Jersey.
2 Darton, Bull. U. S. Geological Survey No. 67, p. 22; Kiimmel, Ann. Report Geol. Survey of N. J., 1897, p. 125.
39
J. VOLNEY LEWIS
DOUBLE CREST OF SECOND WATCHUNG MOUNTAIN 41
NTAINS
= 3 HE a
z
aorotnin| sn | L ’ ll (
42 J. VOENEYV LEWIS
intercurrent warping here advocated. ‘The last is somewhat more fully presented and its bearings upon subsequent geologic history discussed. ‘The others are summarized from Kiimmel’s report.?
1. Conditions requiring explanation.—The width of outcrop of trap along Second Mountain varies greatly. Along much of its course the crest is double, as pointed out above, and in the intervening valley shale has been found at a number of places either in wells or at the surface. At both ends of the ridge, however, the crest is single, and no shales appear within the trap area in the gorge of the Passaic River at Little Falls. In a well at Mount St. Dominic Acad- emy, Caldwell, the following section was found: Glacial drift, too feet; trap rock, 775 feet; total 875 feet; shale at the bottom. A well bored for Mr. Keane on the inner crest. of Second Mountain, near East Livingston, and but three miles from the well at Caldwell, furnished the following section: soil, 5 feet; trap rock, 90 feet; brown sandstone, 51 feet; trap rock, 381 feet; total, 527 feet. Both wells are in such location as to pass through an interbedded layer of sediments, if such existed. Over the country between the two crests Darton found red shale fragments which he regarded as portions of underlying sediments.
2. The interbedded shale hypothesis.—Kiimmel considered the hypothesis that Second Mountain consists of two successive flows of lava separated by a stratum of sediments, but rejected it for the fol- lowing reasons: (1) the crest is single at both ends of the ridge; (2) no trace of shale is found at either locality; (3) the gorge at Little Falls and the deep well at Caldwell show no shale. The “brown sandstone” reported from Mr. Keane’s well he regarded as probably a red-brown variety of trap.
3. The hypothesis of a “curved longitudinal jault.”—Under the seeming necessity of choosing between the interbedded shale hypothe- sis above referred to and that of a fault which possesses the remark- able property of conforming exactly with the present outcrop around the sharply recurved southwestern extremity of Second Mountain, both Darton and Kiimmel accepted the latter, in spite of the fact that “no direct evidence of faulting beyond that furnished by the topog- raphy—the repetition of the beds—was found..... Indirect
1 Loc. cit., pp. 125 ff.
nn i
eo _wa eer SaaS
DOUBLE CREST OF SECOND WATCHUNG MOUNTAIN 43
evidence derived from a study of the width of the outcrop of the trap and the apparent thickness along different section lines” may be summarized as follows: On the assumption (1) that there was no deformation in the intervals between the various lava flows of the Watchung ridges (nor accompanying the flows); (2) that sedimenta- tion was uniform throughout the area; (3) that the lava sheets are approximately of uniform thickness, their bases must have been originally parallel. Allowing for known faults this is still true of First and Second mountains; but from the base of the Second Mountain sheet to that of the third (Long Hill) is a distance that varies greatly in different sections, and the apparent differences are greater where the double crests of Second Mountain are most marked. ‘This variation is ascribed to faulting which Darton assumed further to be confined to the areas of the present trap outcrop.
Kiimmel points out several very obvious defects in the above reasoning: (1) that any or all of these various assumptions may be incorrect; (2) that there is no conclusive reason for supposing that faulting is restricted to the trap areas of the present surface; (3) that variations in thickness of either the trap of Second Mountain or of the overlying shales would vitiate the conclusions. Notwithstanding these elements of uncertainty and improbability, however, the estimates based on the above assumptions are regarded as “indicating quite clearly that some faulting has occurred,” and as ‘‘strengthening the argument derived from the double crest.’’ Hence the conclusion that “‘it is safe to assume that Second Mountain is traversed for much of its extent by a curved longitudinal fault.”
4. The hypothesis of double flow with intercurrent war ping.—The explanation here advanced is believed to be entirely consistent with all ascertainable facts and to be free from improbable assumptions. It is practically the interbedded shale hypothesis described above, freed from the restrictions of stability and uniform sedimentation in the intervals between the lava flows.
The present condition of the Newark rocks throughout eastern North America shows that they have been subjected to universal deformation, and as yet there has been discovered no means of defining the exact stage in their history at which the disturbing movements began. ‘The slightest warping of the surface at any stage
44 J. VOLNEY LEWIS
of the sedimentation would have its inevitable effect upon the thick- ness and distribution of the subsequent deposits. This is particularly true of shallow water and continental formations, in one or both of which categories the Newark beds must be placed.
The proposed hypothesis to account for the conditions above enumerated in Second Mountain may be stated as follows: After the eruption of the trap sheet of First Mountain and the deposition of some 600 feet of overlying sandstones and shales, a second eruption occurred, forming a lava flow averaging probably 500 feet thick over the same region. This is the trap of the outer crest of Second Moun- tain. With this outflow began a gradual depression of the southern axial region of the great Passaic Basin syncline, the region northeastward from Somerville. In consequence of this warping, subsequent deposits were concentrated in this region, tending to build it up to the level of the adjoining area, but before this condition was finally attained depo-
SD Wane WD ZA SITEEZEZ ZI. WNW Fi
Sediments AQ Trap Fic. 3
sition was again interrupted by eruption. Another lava sheet of about 500 feet average thickness was spread over the region, but not uniformly nor even approximately so, as the preceding flow had been. Over the shales in the area of subsidence the maximum thickness was at least 800 feet, while in the adjoining regions where it rested on the unburied flanks of the preceding flow it probably did not exceed 200 feet in thickness. ‘Thus the two flows, separated by a brief interval of deposition, merged into one on the sides of the incipient syncline, but were elsewhere separated by a thin stratum of shale. (See section Fig. 3.) This refers, of course, to the portions of these sheets still preserved to us, all of which are involved in the Passaic Basin syn- cline.
When by later movements their upturned edges were exposed to the forces of weathering and erosion, the soft interbedded shales quick- ly wore away to a lower level, thus forming the continuous valley curving conformably with the outcropping edges of the adjacent trap sheets above and below. ‘The valley between the crests of Second Mountain
eT
DOUBLE CREST OF SECOND WATCHUNG MOUNTAIN 45
is therefore considered to be exactly comparable to Washington Valley, between First and Second mountains. It is shallower and the escarp- ment of the overlying trap outcrop is less pronounced because of the limited thickness of the interbedded shales.
Evidence of continued depression in the same synclinal region is found in the sediments between Second Mountain and the overlying trap sheet of Long Hill. There is a decrease of one-fourth in the thickness of the intervening shales at Madison, as compared with those at Millington, and a much more rapid thinning out toward the west. The trap sheet of Long Hill is also thicker about Millington, but this may be due in part only to the original inequality of the sur- face upon which it was laid.
SECTION OF) TEE MANETUS: -EIMESTONED Xie edb, NORTHERN END OF THE HELDERBERG PLATEAU
CHARLES S. PROSSER Ohio State University
The Helderberg Mountains, or more properly plateau, form a prominent topographic feature of eastern New York the northern escarpment of which is very conspicuous to the south when traveling by electric or steam car between Schenectady and Albany.
Stratigraphic geology in America had its beginning in Albany and Schoharie counties, New York, so that for many years the Helderbergs have been classic ground for geologists. Near the northern end, about south of Meadowdale on the Delaware & Hudson railroad, a highway known as the Indian Ladder road climbs the steep escarpment and this section has been visited and studied by many geologists. Several years ago the writer described this section;* but at that time the limestones forming the conspicuous cliff were known as the Tentaculite and Pentamerus. It was attempted to separate these two formations according to the original definition of Gebhard and later description of Mather; but since the line of division was not very clearly indicated in the original description perhaps the writer was not altogether successful in locating the line of separation used by those early geologists. After the preparation of my paper, geographic names were substituted for those based upon the generic names of inclosed fossils and Vanuxem’s ‘‘ Manlius water-lime group,”’ shortened to Manlius lmestone, replaced the Tentaculite limestone, and the new name of Coeymans limestone was proposed to replace the Pentamerus.? Later, Professor G. D. Harris studied the Helderbergs and published a general section, ‘based largely on the outcrops near Indian Ladder,” together with four special sections. Mr. Christopher A. Hartnagel, assistant
« Kighteenth Ann. Rept. State Geologist [N. Y.], pp. 53-50.
2 Science, IN. S., Vol. X,; Dec, 1890, pp. 876, 377.
3 Bull. Am. Paleontology, No. 19, 1904, Pl. 1, and pp. 24-26.
46
ee
MANLIUS LIMESTONE OF HELDERBERG PLATEAU 47
geologist of the Geological Survey of New York, also studied the Indian Ladder cliff and sent me a detailed section from the top of the ‘‘Hudson River” sandstone to the base of the Coeymans lime- stone, and recently the writer spent a day in a re-examination of that part of the section. The typical section near Manlius has also been examined and after this study it is apparent that the line of division between the Manlius and Coeymans limestones in the Indian Ladder section ought to be drawn higher than it was in the section published by the writer in his article of 1901. This probable change was indicated by the writer in a footnote on p. 290 of Pro- fessor Amadeus W. Grabau’s “‘Guide to the Geology and Paleon- tology of the Schoharie Valley in eastern New York.”!
The following section is based to some extent on one furnished by Mr. Hartnagel, but it has all been remeasured and verified by the writer and on account of the importance of the Helderberg section in geological literature it is considered worthy of publication.
Thickness Total
No. of Zone— Thickness— Feet Feet eye Bluish-gray, coarser-grained limestone than 36+ 95+
the subjacent beds which is limited at the base by a rather marked bedding plane. In the lower 13 feet Mr. Hartnagel reported Stroph- onella punctulifera (Con.) Hall, Spirifer van- uxemi Hall, and Leperditia alta (Con.) Hall. Gypidula galeata (Dal.) H. and C. appears above the 1}-foot zone and within 5 feet becomes abundant. At the base is a coral resembling Cyathophyllum. ‘The lower 2 feet of this divi- sion Professor Harris called “‘ Transition layers,’’? and this name for the zone is quite appropriate since, lithologically, the rock is bluish-gray in color and coarser grained than the subjacent Manlius limestone; but on the other hand it con- tains Spirifer vanuxemi Hall and Leperditia alta (Con.) Hall, which are generaily considered as characteristic of the Manlius limestone, while
t New Vork State Museum, Bull. 92, 1906, 386 pages, 225 figs., 24 pls., and
“Geologic Map"of the Schoharie and Cobleskill Valleys.’”” This comprehensive hand-
book on the geology of the Schoharie valley and northern Helderbergs will prove of inestimable value to students of this classic region.
2 Bull. Am. Pal., No. 19, p. 25.
48
No.
12.
If.
CHARLES S. PROSSER
Gypidula galeata (Dal.) H. and C., the charac- teristic fossil of the Coeymans limestone, was not noted until just above this zone. In this cliff it is evident that the line of division between the Manlius and Coeymans limestones is not sharply marked. The most clearly marked physical change is at the above-noted bedding plane, where Mr. Hartnagel prefers to draw the line of division between these two formations which, in some respects, appears to be the most satisfactory line of division. In the Indian Ladder highway cut from this bedding plane 36+ feet of Coeymans limestone was measured.
Manlius limestone.—From this horizon the subjacent rock undoubtedly belongs in the Man- lius. At the top is frequently a blue, thin- bedded limestone about 6 in. thick, which con- tains Leperditia alta (Con.) Hall. The color is dark blue like that of the Tentaculite limestone. This is No. 2 of Professor Harris’ section. Be- low is a Stromatopora bed which, on the cliff some rods to the east of the “‘ladder,’”’ varies in thickness from 13 to 24 feet. This is No. 3 of Professor Harris’ section which is 3.1 feet in thickness where he measured it, a quarter of a mile west of the ‘‘ladder,”’ while in the cut on the highway 4 feet was obtained and Spirijer van- uxemt Hall was noted.
Dark blue, somewhat irregularly bedded limestone, the lower part of which is generally quite massive, but the upper 13 to 2 feet is thinner bedded and contains Leperditia alta (Con.) Hall. The thickness of this zone varies along the cliff from 5 feet, some distance east of the “‘ladder,” to 54 feet in Hartnagel’s section, 6 feet in Harris’, where it is No. 4, and 6} feet in the highway cut. The most conspicuous lithologic break in this portion of the cliff occurs at the base of this zone; but the color of the rock and its fauna ally it more closely with the Tent- aculite than the Pentamerus limestone.
Thickness of Zone— Feet
ian
Total
' Thickness—
Feet
59+
56
Io.
MANLIUS LIMESTONE OF HELDERBERG PLATEAU 49
Cement beds which are compact, even bedded, and generally weathered back a foot or two, and sometimes several feet within the face of the cliff. This zone, as a rule, is conspicu- ously shown on the face of the escarpment. Its thickness is somewhat variable, ranging from 4 feet, 9 inches, at the first spring east of the high- way to 3 feet in Harris’ section. It is given as 44 feet by Hartnagel and on the Indian Ladder road it is 3 feet, 9 inches. In my former paper this zone formed the upper part of what was termed the transitional beds from the Tentacu- lite to the Pentamerus limestone; but it was included in the Tentaculite limestone. They were termed transitional because Tentaculites gyracanthus Eaton, the characteristic fossil of the Tentaculite limestone, was not found in them, while some of the other Tentaculite fossils were found well toward their top and the marked lithologic break at the top of the cement zone was thought to represent the line of division be- tween these two limestones as used by the older geologists. At the base of the cement rock is generally a shaly limestone, about 6 inches thick, which frequently shows ripple marks. The dis- tance from the top of this zone to the base of the Manlius limestone may be easily measured in the cliff near the first spring east of the Indian Ladder road.
Massive rough limestone containing Strom- atopora in which Mr. Hartnagel reported Spirijer vanuxemt Hall and Leperditia alta (Con.) Hall.
Thin-bedded limestone with Stromatopora layer at base. These two zones correspond to No. 6 of Harris’ section with the same thickness.
Massive compact layer.
Thin-bedded, dark-blue limestone which has a metallic ring. Many of the layers contain immense numbers of Tentaculites gyracanthus Eaton.
Thick and thin layers of dark-blue lime-
Thickness of Zone— Feet
4it
Total Thickness— Feet
5 Ors
50 CHARLES S. PROSSER
Thickness Total No. of Zone— Thickness— Feet Feet
stone with a thickness of 6% feet and perhaps it it may reach 74 feet. A massive layer near the middle of this zone, according to Mr. Hartnagel, contains abundant specimens of Modiolopsis dubius Hall and Leperditia alta (Con.) Hall while Spirijer vanuxemi Hall is common. The base of this zone marks the bottom of the Man- lius limestone with a total thickness of 544+ feet in the above section.
4 Soft seam of shaly, much-decomposed mate- rial about $-inch thick. This layer appears all along the exposure at the first fall and the second spring west of the ‘‘ladder.”’ The overlying layers are all regular, so that this one marks a change in deposition and, apparently, a forma- tional line of division.
3° Dark, contorted, seamy limestone with ap- 1o+in. 4h
pearance of gypsum rock which, on examination, Mr. Hartnagel reports to be a sandy limestone with some clayey material; but no gypsum. This zone has a variable thickness and is more or less irregular.
2 Layer containing much pyrite and many 33 ft. 34 seams of calcite, where pyrite is abundant, weath- ering to a dirty yellow color. The rock contains frequent cavities, is broken, or has irregular structure.
Te “Hudson River” sandstone, thickly bedded and very quartzose at top, dark olive-gray color, with pyrite scattered through the rock in small crystals.
3+
nie me 5
ay
w
In my former section the rocks corresponding to Nos. 2 and 3 of the above section were referred to the Waterlime (Rondout)? which was accepted by Professor Schuchert in his discussion of the same section.? Professor Harris, however, stated that at this locality “there are four or five feet of gypsiferous and pyritiferous shales, resembling in many ways the Salina beds beneath the Cobleskill
t Kighteenth Ann. Rept. State Geol. (N. Y.], p. 54. 2 Am. Geol., Vol. XXXI, 1903, p. 172. :
MANLIUS LIMESTONE OF HELDERBERG PLATEAU 51
at Howe’s Cave.”* Mr. Hartnagel carefully examined these beds, failed to find gypsum, stated that the association is quite different from that of the pyrite layer (Salina) at Howe’s Cave, and concluded that it was more in harmony with known facts to refer these layers (Nos. 2 and 3) to the Rondout.
The Manlius limestone is regarded as beginning with the base of No. 5 and extending at least to the top of No. 12, and perhaps a foot and a half higher, with a total thickness of 544+feet. This thickness is 84 feet greater than the sum of the Tentaculite and transitional beds as given in my paper of rgot, due to the addition of Nos. 11 and 12 of the above section which have a united thickness of about 9 feet. If to the 544+ feet which I have given as the thickness of the Manlius there be added the overlying transition layer of Harris, which he gives as 2 feet, then the thickness of the Manlius limestone will become 564+feet and the measurements of Harris and myself identical in the Indian Ladder cliff.
The thickness of the Pentamerus limestone in the t9o01 paper was given as from 49 to 52 feet along the Indian Ladder cliff and subtracting the lower 9 feet, which is now put in the Manlius, there remains between 4o and 43 feet for the Coeymans limestone.
It is also probably true that in the Countryman Hill section by Pros- ser and Rowe? a similar 9 feet ought to be taken from the base of the Pentamerus limestone and added to that of the Tentaculite to make the total thickness of the Manlius limestone, in accordance with the section of that hill given by Professor Harris.3 The writer has not been able to re-examine this section, but if the above change be made then the thickness of the Manlius limestone in the Prosser and Rowe section will become 55 feet and that of the Coeymans limestone, 41 feet.
t Bull. Am. Pal. No. 19, p. 25.
2 Seventeenth Ann. Rept. State Geol. [N. Y.], 1899 [1900], pp. 329-42.
3 Bull. Am. Pal., No. 19, p. 26.
NOTE ON THE RED BEDS OF THE RIO GRANDE REGION IN CENTRAL NEW MEXICO:
WILLIS T. LEE
During the summers of 1904 and 1905 the writer was engaged in geologic investigations in the Rio Grande valley in central New Mexico. The results will be set forth in detail in the near future, but a preliminary statement is here given of certain facts which throw some light on the complex problems of the Red beds.
There are exceptional opportunities for geologic observations in the Rio Grande valley. The region is one in which many monoclinal or block mountains occur, having precipitous, scarp-like faces in which the various geologic formations, ranging in age from pre- Cambrian to Quaternary, are conspicuously exposed. The Red beds here described outcrop at the surface with minor interruptions from Galisteo Creek at the southern end of the Rocky Mountains, southward to Rincon, a distance of about 200 miles. They were examined with care in many places east of the Rio Grande, notably in Galisteo canyon; at the northern end of Sandia mountains; in Abo canyon east of Belen; in the mountains east of Socorro; in San Andreas mountains east of Engle; and in the Caballos-Fra Cristobal range north of Rincon.
Throughout this distance the Red beds are uniform in character, consisting usually of three more or less distinct divisions. The lowest division is composed principally of massive, dark red sandstone, with a maximum observed thickness of about 800 feet. The middle division consists of pink and white shale and gypsum, with a sub- ordinate amount of limestone. ‘The limestone is not always present, and the gypsum varies in thickness. In some places, as in Galisteo canyon at the northern end of the region, the massive gypsum is about 140 feet thick, with the accompanying shale inconspicuous and the limestone practically absent. In other places the gypsum is distributed in thin beds through a considerable thickness of shale
t Published by permission of the Director of the U. S. Geological Survey. 52
RED BEDS OF RIO GRANDE REGION 53
and limestone, as is the case in San Andreas Mountains east of Engle, where the gypsiferous division is nearly 1,000 feet thick. The upper division, consisting of alternating layers of yellow, pink, and white sandstones and shales, has an observed thickness of many hundreds of feet, but is not always clearly differentiated from the middle or gypsiferous division.
The Red beds of the Rio Grande region are similar in general appearance and lithologic character to the red sandstone formation occurring along the eastern base of the Rocky Mountains, and extending thence eastward across southern Colorado and New Mexico. In other words the red sandstones and shales of the Rio Grande region form part of the complex which is frequently called ‘“‘the Red beds” of the Rocky Mountain region.
In the Rio Grande region the Red beds rest unconformably upon an extensive series of Upper Carboniferous limestones. At the base. of the red strata occurs a limestone conglomerate, the pebbles of which contain fossils identical with those of the limestones upon which the conglomerate rests. ‘This was observed in the hills east of Socorro, in Abo canyon east of Belen, and at the northern end of Sandia Mountains. ‘Twenty-five to seventy-five feet above this basal conglomerate occurs a persistent limestone member containing a rich fauna. Collections were made from this limestone in several localities.
Many of the limestones of the middle or gypsiferous division are also very fossiliferous, and large collections were obtained from them in widely separated localities. ‘The upper division, so far as observed, is sparingly fossiliferous, and not faunally different from the under- lying or middle division. But overlying it in the southern half of the region occurs a limestone several hundred feet thick, which yielded an abundant fauna. This overlying limestone is absent in the northern part of the region, but occurs in the central part and apparently thickens toward the south. It is well-developed in the mountains east of Socorro, in the San Andreas Mountains east of | Engle, in the Caballos-Fra Cristobal Range, and elsewhere. On account of its important bearing on the age of the underlying Red beds, fossils were collected from it in about thirty separate localities.
The fossil collections from the various horizons are too voluminous
54 WILLIS T. LEE
to be described in this note, and discussion of them is reserved for the more extended report to follow. Dr. G. H. Girty,* of the Geo- logical Survey, who has examined them, states that the faunas from the Red beds are Upper Carboniferous, although they are sharply distinct from those of the underlying limestones which are also Upper Carboniferous. He states further that the fauna of the limestone overlying the Red beds is also clearly Carboniferous and probably older than the Guadalupian fauna. In other words, all of the 2,000 feet or more of the Red beds just described in the Rio Grande region are Carboniferous, and probably older than the Guadalupian or so-called Permian of western Texas.
No red sediments were observed immediately overlying the upper- most Carboniferous limestone. In some of the southernmost expos- ures, particularly in the Caballos Mountains, this limestone is over= lain by dark-colored shales in which Benton fossils‘ were found about 200 feet above the Carboniferous limestone.
At the northern end of the region in Galisteo canyon the triple division of the Carboniferous Red beds is characteristically developed, although the exposed thickness is much less than it is farther south. Only the upper 250 feet of the lower or massive sandstone division is exposed. The gypsum is here about rqo feet thick; and the upper or pink division, consisting mainly of sandstone, is 300 feet or more in thickness. No fossils were found in the Red beds at this place, but large collections were obtained from the lower division near Tejon, about 12 miles south of Galisteo Creek.
The limestone which overlies the pink sandstones in the southern part of the region, and which has just been described as the highest horizon at which Carboniferous fossils were found, does not occur in Galisteo canyon. About 200 feet of variegated shales and sand- stones, having the same general appearance as the Morrison forma- tion, overlie the pink sandstones and are separated from them by what appears to be an unconformity of erosion. This was seen in only one place. The variegated shales are overlain by a massive white friable sandstone about 60 feet thick and similar in appear-
t Personal communication. t The Cretaceous fossils referred to here and elsewhere in this paper have been identified by Dr. T. W. Stanton.
RED BEDS OF RIO GRANDE REGION 55
ance to the sandstone which, in eastern Colorado and New Mexico, has frequently been called the lower Dakota, but which, as Stanton" has shown, underlies fossiliferous Comanche in the plains region, and in the foothills of the Rocky Mountains at Canyon City, Colo. This sandstone is followed in turn by fossiliferous sandstones, shales, and limestones representing the principal subdivisions of the Upper Cretaceous section of the eastern Rocky Mountain region, with the possible exception of the Dakota.
In the central part of the region described, although known Car- boniferous Red beds were observed in several places with fossiliferous Benton in the same section, no red sediments were observed which could be referred to the Triassic. This fact is significant, since Triassic Red beds are known to occur in the Gallinas Mountains,? about 60 miles northwest of Galisteo canyon, and in the plains region of eastern Colorado and New Mexico, ‘Triassic vertebrates have been reported by Darton’ in the Red beds of Purgatory canyon in southeastern Colorado, and by Stanton‘ in the Rio Cimarron canyon of eastern New Mexico. The writer has also found them in the northern breaks of the Staked Plains in eastern New Mexico.
The latter occurrence has not heretofore been described. The fossil bones were found at E, O. Davis’ ranch, about 20 miles south- east of Tucumcari. They occur at the top of the Red beds, overlain at this point by plains-Tertiary, but covered half a mile farther north by yellow sandstones and shales containing Gryphaea corrugata Say and other characteristic Comanche fossils.
Invertebrates of probable Triassic affinities have been reported from the red beds of the Canadian valley by Stanton,5 who in com- pany with the writer obtained a collection of them at Henry Hunikes ranch on the Rio Concho, about 30 miles southeast of Las Vegas.
tT. W. Stanton, ‘‘The Morrison Formation and Its Relations with the Comanche: Series of the Dakota Formation,” Journal of Geology, Vol. XIII (1905), pp. 657-69.
2 E. D. Cope, Monographs, U. S. Geographical and Geological Surveys West of tooth Meridian, Vol. IV, Part II, “Report upon the Extinct Vertebrata Obtained in New Mexico by Parties of the Expedition of 1874, 1877,” pp. 5-13.
3N. H. Darton, ‘‘Preliminary Report on the Geology and Underground Water Resources of the Central Great Plains,”’ U. S. Geological Survey, Professional Paper No. 32, 1905, p. 159.
4 Op. cit., p. 665. 5 Ibid., p. 666.
56 WILLIS T. LEE
The shells occur about 500 feet below the top of the Red beds as exposed in the Canadian escarpment 5 miles to the west. Stanton? states that the collection contains two species belonging probably to the genus Unio and comparable, though apparently not identical, with the species of Unio described by Meek from the Triassic of Gallinas Creek, New Mexico, and by Simpson from the Dockum beds in western Texas. Regarding the age relations of these inver- tebrates, Stanton states that “the occurrence of Unio in these Red beds is considered sufficient evidence of their post-Paleozoic age, from the fact that the genus is not known to range elsewhere below the Mesozoic, and, with the exception of these forms described by Meek and Simpson, it has not been recorded in beds older than the Jurassic.”
_ Since the Red beds at no great distance both east and west of the Rio Grande region are in part at least Triassic, it is somewhat surprising that all of the 2,000 feet or more of the Rio Grande Red beds (except the late Cretaceous red series described below) should prove to be older than the Permian. It is possible that further investigation may reveal the presence of younger Red beds in locali- ties not yet examined in the Rio Grande region, but, judging from the evidence at hand, it is more probable that, in case Triassic and Permian beds were ever deposited in this region, they were eroded away prior to the deposition of the Upper Cretaceous sediments.
A second or younger red series occurs in the Rio Grande valley which has sometimes been confused with the Carboniferous Red beds just described. It is perhaps best exposed near Elephant Butte, west of Engle, N. M., where it consists of shale, sandstone, and conglomerate more or less highly colored and several hundred feet thick. It is well exposed only where the Rio Grande and its tributary streams have eroded into it between the Caballos and Fra Cristobal Moun- tains. It is exposed close to a zone of intense faulting, and probably for this reason has been erroneously interpreted as a part of the older or Carboniferous Red beds brought to the surface by faulting.
The red sediments at Elephant Butte are very similar in general appearance to the Carboniferous Red beds, and might be easily mistaken for that formation until examined closely, when they are
Personal communication.
RED BEDS OF RIO GRANDE REGION 57
found to differ in composition from the older beds and to lie strati- graphically above fossiliferous limestones and shales of Upper Cre- taceous age. At the northern end of Caballos mountains, two miles south of Elephant Butte, the Upper Carboniferous formations, including the older Red beds, together with their underlying and overlying limestones, occur overlain by fossiliferous strata of the Benton formation, which in turn is followed by an extensive series of Cretaceous sandstones, containing beds of coal at its base, and great quantities of fossil wood at higher horizons. ‘The leaves and tree trunks of both monocotyledonous and dicotyledonous varieties are numerous. Palm wood is particularly abundant.
The red sandstones and shales constitute the uppermost exposed member of the coal-bearing sandstones and, in addition to the fossil plants, contain Dinosaur bones. No excavations were made in order to secure satisfactory material for specific determination, but Mr. J. W. Gidley, of the National Museum, who examined the collections, states that the Dinosaurs belong to the genus Tviceratops, clearly indicating that these red beds are of late Cretaceous age.
A similar series of red sandstones and conglomerates occurs at the northern end of the region, and was observed above the coal- bearing sandstones near Cerillos, and again near the Hagan coal- fields, a few miles south of Cerillos. In both of these localities the red sediments occur at the top of the Upper Cretaceous section and contain great quantities of petrified wood, but are otherwise unfos- silferous, so far as known.
The conglomerates of this formation are made up of pebbles, of various igneous and metamorphic rocks, together with limestones containing Carboniferous fossils, and red sandstones similar to those of the older or Carboniferous Red beds. Many of the pebbles are only slightly rounded and were apparently transported but short distances. The upper part of the formation, throughout an exposed thickness of about 200 feet near Hagan, is a conglomerate composed mainly of fragments of andesite.
This formation was originally described by Hayden? as the Galisteo sands. On account of the strong resemblance in physical character,
t F. H. Hayden, U. S. Geological Survey of the Territories for 1867, 1868, and 1869, reprint 1873, p. 166.
58 WILLIS T. LEE
stratigraphic position, and general appearance, the Galisteo forma- tion is here regarded as probably a time equivalent of the Triceratops or late Cretaceous red beds of the Elephant Butte region.
In concluding I would emphasize the fact that there are two red formations in the Rio Grande region, which resemble each other so closely in places that careful observation is sometimes necessary in order to distinguish between them; and that neither of these forma- tions belongs to the Jura-Trias or Permian, to which they have frequently been referred, the older one belonging to the Pennsylvanian system, and the younger one to the Upper Cretaceous.
U. S. GEOLOGICAL SURVEY, WASHINGTON, D. C., June 28, 1906
STUDIES IN THE DEVELOPMENT OF CERTAIN PALEO- ZOIC CORALS
G. E. ANDERSON Columbia University, New York
ON THE ORIGIN AND DEVELOPMENT OF THE INNER WALL
Certain Paleozoic corals have been characterized by their authors as containing an inner wall which divides the corallite into an inner central and an outer annular area, the latter extending between the two walls. It has also been observed that in a number of these genera the septa extend to the center, penetrating the supposed inner wall, while in others the septa terminate in the inner wall itself. ‘The genus Acervularia is a type of the former and Craspedophyllum' of the latter. The character of the inner wall in the two types is such that they can readily be differentiated even in a very cursory examination. While both genera have been considered to contain an inner wall, Edwards and Haimes as early as 1850 (Polyp. Foss. des Terr. Paleoz.) differentiated the two types by noting that the internal structure of Eridophyllum, which is of the Craspedophyllum type, differed from Acervularia in that the septa terminated in the inner wall, while in the latter the septa extended through the inner wall into the inner central area. ‘They do not record having noted any difference in the structure of the inner walls themselves in the two genera.
Thin sections reveal the fact that the structure of the two types of wall are quite different and that they have an entirely different origin. The inner wall in the Craspedophyllum-Eridophyllum type is of a similar nature in texture and thickness to the septa, and occupies but a small central circular portion of the corallite.
In Craspedophyllum the diameter of the inner wall is about one- sixth to one-fifth that of the corallite. In the normal adult of this genus the inner wall has one opening, connecting the central area with the cardinal fossula. This gives to the inner wall the shape
z Equivalent to Thomson’s Crepidophyllum, which term is used by Canadian paleontologists.
59
60 G. E. ANDERSON
of a horseshoe, but in more specialized individuals a bridge span- ning the cardinal fossula gives the inner wall a circular outline and completely separates the inner circular and the outer annular areas. In the Acervularia type* the supposed inner wall is much thicker than the septa and in size about one-half the diameter of the corallite, so that even the tertiary septa take part in its formation and these as well as the secondary septa may extend into the inner central area. The supposed inner wall thus formed is not of uniform thickness, being thicker at the intersection of the septa: in some individuals the thickening from each septum is not sufficient to be in contact with the thickening from the neighboring septum, thus giving a number of openings in the wall. This is readily accounted for when it is seen that the apparent wall is formed by the lateral thickening of the septa at or near the end of the tertiary septa. When sufficient thickening of the septa occurs, they will be brought in contact, giving the appear- ance of an inner wall. It is evident that the supposed inner wall of this type is rather of the nature of a pseudotheca, the portion of the septa between. the region of the septal thicken- ing and the outer wall corresponding to the costae, thus differing greatly from the corals containing a true inner wall. We may now inquire into the nature of the inner wall itself as present in such Fic. 1.—Cross-section of a % S€Nus as Craspedophy llum. The young corallite of Craspedo- Devonic species, Craspedophyllum sub- phyllum subcaespitosum Diam- ges pitosum, from the Hamilton of Thed- eter ann. a. ‘The alar septa. ford, Ontario, is here chosen, as it is one c. The cardinal septum. D d y Showing the early grouping of Which is especially distinguished as show-
the septa. Four openings are jing the typical structure of the true inner shown but the normal condi- wall
tion is three, the two alar and aie the one at the cardinal fossula. The mode of origin and development
can be understood by comparing a series of figures (Figs. 1-5) representing the development of the inner wall
1 This refers to description of the type of Acervularia. In some specimens of Acervularia in this country there is no lateral thickening of the septa, and hence no indication of the supposed inner wall.
DEVELOPMENT OF PALEOZOIC CORALS 61
as revealed in successive sections of a single corallite. It is seen that each alar region is that at which new septa are successively added to the primary septa (Fig. 1).
The addition of new septa takes place in such a manner that the new short septa are inclined toward the older, with which they are permanently fused with their inner borders, never being detached even in the most developed stages. It is to this persistent fusion of the inner borders of the long septa that the inner wall is directly due, as will be explained presently. It is evident that the addition of new septa is the same as Duerden has found to be true in the genus Streptelasma (Biological Bulletin, Vol. IX, No. 1, p. 30), but that genus differs from Craspedophyllum in that the septa become free toward the close of development. It differs from the genus Hadrophyl- lum, as in the latter the alar pseudofossulae’ and the pinnate arrange- ment of the septa are maintained in the most developed stages, whereas in Craspedophyllum the alar pseudo-fossulae become obliterated very early in the life of the individual by the formation of a dissepi- mental bridge, and the pinnate arrangement of the septa, with the exception of one or two septa on either side of the cardinal fossula, gives place to the more specialized radial arrangement.
The growth of septa in the early stages is very rapid, but the central -area is always left intact never being invaded by them. This gives the septa an irregular appearance which greatly adds to the difficulty of detect- ing the Streptelasma mode of arrange- ment; the difficulty being further ‘augmented by the tendency of the septa to arrange themselves radially Fic. 2.—Section of same coral- andeyvet to) nemaimvattached withthe lcyo0 ) seh UP. Diameter 9 : ; 3mm, a. The alar septa.- The innem borders: aplt_issevidentsthat ior a. ap pcay. con iecicg oath the septa to remain attached in this the inner central area. -manner, only the peripheral portion can become radial at first, but this portion gradually extends inward until
t Grabau and Shimer, North-American Index Fossils, p. 48.
62 G. E. ANDERSON
finally it reaches a point where it will be nearly at right angles to the inner part or attached border, which is at this time about parallel in position to the outer wall. This inner portion of each septum in this manner forms a part of the inner wall as fast as the septa become radially directed (Figs. 2, 3).
In a later section (Fig. 2) the alar pseudo-fossulae have been spanned by a dissepimental bridge which is here slightly thinner than the normal width of the inner wall. The inner wall ends in two septa, one on each side of the cardinal septum as would be expected, unless the latter should take part in the formation of the inner wall which, however, has not been observed.
In a section of a later stage (Fig. 3) the inner wallisof uniform thickness and ends in the septa nearest the cardinal fossula, as in Fig. 2. The neck between the cardinal fossula and the inner central area has become more narrow. ‘The cardinal septum has been reduced in size to that of a tertiary septum.
This mode of development of the inner wall extends from the
: alar septa as initial points
taken 5™™ higher up than section of 5 z Fig. 2. a. Thealarsepta. Diameter towards the cardinal eo and of corallite, 4m™, simultaneously from either side of the counter septum as another initial point toward the two alar regions. There would, therefore, be a break in the inner wall in the region of the cardinal septum, and two breaks, one at each of the alar regions where growth from the counter quadrants ceased. The two latter are early spanned by the deposi- tion of material of a similar nature to that of the septa, thus uniting the groups and making the septal structure more firm. In Fig. 2 this growth is in the course of construction and is completed before the stage in Fig. 3 is reached, as here the wall is of uniform thickness throughout—and the “bridges” spanning the pseudo-fossulae in Fig. 2 are thoroughly incorporated. This eliminates the last trace of the
Fic. 3.—Section of same corallite
DEVELOPMENT OF PALEOZOIC CORALS 63
alar pseudo-fossulae, and all the septa have assumed their complete radial direction with the exception of one on either side of the cardinal fossula.
The opening in the inner wall in the region of the cardinal fossula is very persistent and remains permanently in normal individuals of the species, constituting the character of the horseshoe shaped inner wall of Craspedophyllum (Fig. 4.) In normal types it persists into the adult, but in the last stages of accelerated types it is closed. While this opening remains, the two septa on either side of the car- dinal septum remain pinnate and form the ends of the incomplete wall (Fig. 3). The septa very slowly arrange themsvlves radially and in a similar manner to the earlier ones contribute their por- tion to the ends of the inner wall (compare Figs. 3 and 4). ‘The septa on either side of the car- dinal septum are now more radially arranged than in Fig. 3, and the connection between the inner central areaand the cardinal fossula is more constricted. It is seen in Fig. 4 that as these two septa become radially directed, the neck connecting the cardinal fossula with the inner central Fic. 4.——Cross-section of the same area is gradually constricted until corallite taken 5mm higher up than
: : Fig. 3. Diameter 4™™. a. The alar a stage 1s reached, as shown in septa. A slight irregularity of growth Fig. 5, when this neck is spanned on the left. by a similar dissepimental bridge which early in the life of the individual cut off the connection between the alar pseudo-fossulae and the inner central area. It is evident that in further development of the individual, the cardinal fossula cannot be distinguished and to all appearance becomes similar to one of the interseptal spaces. The septa on either side of the cardinal septum have now assumed a nearly radial direction and the dissepimental bridge spans the cardinal fossula making the inner wall complete. In Fig. 5 one can clearly trace the
64 G. E. ANDERSON
order of development of the septa by their inner borders retaining a slight indication of the pinnate arrangement in the early stages. Further development of the corallite will tend to make the septa per- fectly radial in direction and the inner wall, to which the primary and secondary septa are still firmly fused, assume a circular outline which is better illustrated in more specialized individuals than is shown in Fig. 5. At such a stage the true relation which exists between the inner wall and the long septa is not so evident. The former now develops quite independently of the septa, the inner borders of which may be considered as fused with the inner wall itself. The inner wall becomes circular at this stage, and it is evident that the cardinal fossula is no longer prominent. The cardinal septum has been reduced in size so as to be equal in length to a tertiary septum.
The tertiary septa do not appear until the secondary septa are well developed (Fig.-1. shows no tertiary septa). These differ from the primary or secondary septa in being radially arranged
Fic. 5.—Cross-section of same corallite from their first appearance in the taken 2™™ above section of Fig. 4. a. The outer wall, and consequently their inner borders are free and can, therefore, easily be distinguished from the secondary septa. They extend one-half the distance to the inner wall before the latter is closed in the region of the cardinal septum, and this constitutes their full growth.
So far only the transverse sections at different stages have been discussed, though the longitudinal section (Fig. 6) is equally interest- ing. The central area is occupied by a series of tabulae the outer
alar septa. c. The cardinal septum. Diameter 5™™.
borders of which are fused in the inner wall, which is circumscribed by a second series of tabulae distinguished from the first series in being more delicate and more crowded. ‘The second series of tabulae are fused with their inner borders in the inner wall, but have no con-
DEVELOPMENT. OF PALEOZOIC CORALS 6
nection with the first series.
UL
Their outer borders extend to the inner-
most series of interseptal dissepiments and these dissepiments occupy
the remainder of the interior to the outer wall.
at irregular intervals, as parallel bars extending inward and up- ward in an arching manner.
The essential characteristics, with the exception of the com- pleted inner wall, are more specialized in the species C. archiact from the Hamilton of Thunder Bay, Michigan. In a single corallum are found indi- viduals representing the several stages of development. Thus are found individuals, in the young stages of which the inner wall has not appeared, others in which it is open at the cardinal septum, and still others in which it is completely closed, which is a rarer feature in this species than in C. subcaes pitosum. When the inner wall is incomplete, the car- dinal septum often extends into the inner central area (Fig. 7). This peculiarity has not been observed in any other species containing a true inner wall. When the wall is completely closed in this species, the cardinal septum extends to the dissepti-
The carinae appear,
C,
TD —
TIT.
Ie Lh
y. @
os SN
oD eee as
MIT) paw myn (| ((
04 a
» ))
Fic. 6.—Longitudinal section cf Cras pedophyllum subcaes pitosum showing the slight tapering of the corallite; and, from the margin toward the center: the interseptal dissepiment; the carinae; the second tabulate area; a section of the inner wall and the central tabulate area.
mental bridge which spans the cardinal fossula, becoming identical with a secondary septum with tertiary septa separating it from the
other secondary septa.
Closely allied to C. archiaci from above locality, is Eridophvllum verneuilanum from Columbus, Ohio, the difference in internal structure
66 G. E. ANDERSON
between the two being such as might readily be expected of different individuals in the same species. This difference lies in the epithecal projections characteristic of Eridophyllum which are entirely want- ing in Craspedophyllum. It seems not unlikely, therefore, that a generic relationship exists between these types. If this be so, Craspedophyllum must be considered as the ancestor. This is further substantiated in the greater specialization of Eridophyllum ver- neuilanum when com- pared with Cras pedo phyl- lum subcaespitosum. Thus the Eridophyllum is more specialized in the early expansion to normal size; in the com- plete inner wall which appears earlier in the life of the individual; and in the additional feature of epithecal projections. If the relationship outlined proves true, it is evident
Fic. 7 = Cross-section of mature specimen of that Erido phyllum ver- Craspedophyllum archiaci, showing the incom- neuilanum cannot be
plete inner wall with the cardinal septum extend- genetically related to the ing into the inner central area.
oe Hee ey
Siluric species, Erido-— phyllum rugosum as the latter makes its appearance before the pos- tulated ancestor of Eridophyllum verneuilanum, i.e.,Craspedophyllum. The characters now relied on for generic distinction being homoeo- morphic, these would represent entirely distinct genera, and not as now generally considered, species of one genus. LEridophyllum rugo- sum requires further investigation, which is rendered very difficult as most material is silicified and the delicate internal structure destroyed.
Other corals with true inner wall.—Hapsiphyllum (Simpson) and Laccophyllum (Simpson) both contain an inner wall; in the former it
DEVELOPMENT OF PALEOZOIC CORALS 67
is incomplete and in the latter complete. They have, however, scarcely any characteristics in common with the corals above considered. In Laccophyllum the wall is very massive and much thicker than the septa, and in both it is conical in shape, decreasing in diameter toward the tip of the corallite. This feature is reversed in the Craspedophyl- lum type, as in the latter the inner wall becomes smaller in diameter as the corallite develops. They are good examples of individuals in remote parallel series.
Carinae.—The carinae are not present at the early stage repre- sented in Fig. 1, but the first series is well indicated in Fig. 2. ‘These are formed by bar-like growths ex- tending upward and inward in an arching manner (Fig. 6), and on cor- responding sides of the septum. In transverse sections they appear as short cross-bars through the septum (Figs. 2,5, 7). The mode of growth and the order of appearance of the carinae will be understood from the diagrammatic section, Fig. 8. The difficulty of obtaining a complete longitudinal section of a septum from a specimen is apparent as these seldom if ever develop in a true plane. The 1. 8.—A longitudinal dia- diagrammatic section is therefore based omen oe ee
with ideal development of the upon the development of the carinae carinz. at different. stages as they are revealed by several longitudinal sections. A general idea is, however, obtained from Fig. 6, where the carinae are revealed in several places. In Fig. 8 it is seen that the tip of the corallite contains no carinae and this would therefore, represent a stage of Fig. 1, or earlier. ‘The first carina appears at the outer wall and grows upward and inward until it finally fades away in the region of the inner wall. As soon as the room is sufficiently large between the first carina and the outer wall, the second carina begins and takes a path similar to the first. A similar direction is taken by each successive carina; all terminating in a like manner, and new ones take their places at the outer wall.
68 G. LE. ANDERSON
It is evident that if AB (Fig. 8) represents a transverse section, there will be four carinae cut and in the order of their appearance these are 9, 10, II, 12, carina number g being the oldest of the four, and carina number 12 the youngest. Hence the oldest carina in any transverse section is the one nearest the center, and they become successively younger toward the outer wall.
Corals with the appearance of an inner wall.—To Strombodes is attributed a rudimentary inner wall by Edwards and Haime (Brit. Foss. Corals, Intr., p. \xx). It does not possess a true inner wall, however, as the coral is composed of superposed lamellae, and the fact that it contains no septa renders the presence of an inner wall impossible. ‘The appearance of an inner wall in Phillipsastrea is the same as that in Acervularia, being formed by pseudo-thecae, and not as the true inner wall. Aulophyllum is considered by Edwards and Haime (Polyp. Foss. des Terr. Palaeoz., p. 413) to contain an inner wall similar to that of Acervularia; hence, it also must be considered as not containing a true inner wall.
In Synaptophyllum (Simp.) and Schoenophyllum (Simp.) the appearance of an inner wall is attributed by their author (Bull. 30, New York State Museum, Vol. VIII, p. 212), to a thickening of the margin of the inner row of dissepiment through which the septa pass and extend with free inner borders nearly to the center. In Depaso- phyllum!* the upturned outer borders of the tabulae, are fused into the lateral area of the short septa forming what appears to be an inner wall which is about two-thirds the diameter of the corallite. The septa are in no way otherwise connected with the inner wall thus formed by the tabulae, and the septa often extend with free inner borders into the central area. The wall is thus formed by the tabulae and not by the inner borders of the septa which is essential in the true inner wall.
The inner wall, as found in the coral containing a true inner wall, which I shall call “‘bimural corals,’’ is defined as formed originally by the inner borders of the long septa. For this reason the long septa, with the exception of the cardinal septum, cannot extend into the inner central area in “‘bimural corals,” by penetrating the inner wall; herein lies the distinction which differentiates it from the Acer- vularia type. A longitudinal thin section through the central region
t Grabau, Geol. and Paleon. of the Devonic Formation of N. Michigan (in press).
DEVELOPMENT OF PALEOZOIC CORALS 69
of the corallite will always disclose the two sides of the inner wall in the “bimural corals” (Fig. 6), which feature also is wanting in the Acervularia type.
BIBLIOGRAPHY
ACERVULARIA (Schweig) Edwards and Haimes, Polyp. Foss. des Terr. Palaeoz., p. 419, Pl. 9, Figs. 4, 4a, 4b, 1851. Brit. Foss. Corals, 1850, p. Ixx. Hall, Report Geol. Surv. Ohio, 1875, Vol. II, Pt. II, p. 476. Nicholson, Geol. Surv. Ohio, 1875, Vol. II, Pt. Il, p. 240. Schweigger, Handb. der Naturg., p. 418, 1820. AULOPHYLLUM (E. and H.) Edwards and Haimes, Brit. Foss. Corals, p. \xx, 1850, Pl. 3. Polyp. Foss. des Terr. Palaeoz., p. 413. CRASPEDOPHYLLUM (Dybowsky) Billings, ““Diphyphyllum archiact.” Can. Jour., Vol. V. p. 260, Fig. 8. Nicholson, “Heliophyllum subcaespitosum,” Geol. Mag., London, 1874, Volsitpa ss Pins hig 0: Nicholson and Thomson, ‘‘Crepidophyllum,’”’ Proc. Roy. Soc. Edinburgh, Vol. IX, p. 149. Thomson, ‘“‘Crepidophyllum,” Ann. Mag. Nat Hist., p. 51, 1878. DIPHYPHYLLUM (Lonsdale) Lonsdale, Murch., Vern., Keys., Russia and the Urals, 1845, Vol. I, pp. 623-24, PI. A, Fig. 4. Clarke and Ruedemann, New York State Museum Mem. V, p. 25. Edwards and Haimes, Polyp. Foss. des Terr. Palaeoz., p. 446. Thomson, J., Quarterly Journal of the Geol. Soc., 1887, p. 33. Hall, “‘Diplophyllum,” Pal. of New York, 1852, Vol. Il, p. 115. Lambe, “Can. Paleoz. Corals,’ Contributions to Canadian Paleontology, Vole Pts We iphans7: ERIDOPHYLLUM (Verneuilanum) Edwards and Haimes, Brit. Foss. Corals, 1850, p. 1xxi. Polyp. Foss. des Terr. Palaeoz., p. 424, Pl. 8, Figs. 6, 6a. HApsIPHYLLUM (Simpson) Simpson, Bull. 39, New York State Museum, Vol. VIII, p. 203, Fig. 10. LAccOPHYLLUM (Simpson) Simpson, Bull. 39, New York State Museum, Vol. VIII, p. 221, Figs. 7, 8, 9. PHILLIPSASTREA (D’Orbigny) D’Orbigny, Note sur des Poypiers fossiles, 1849, p. 2. Edwards and Haimes, Brit. Foss. Corals, Intr., p. xx. SCHOENOPHYLLUM (Simpson) Simpson, Bull. 39, New York State Museum, Vol. VIII, p. 214, Figs. 39, 40. STROMBODES (Schweig) Edwards and Haimes, Brit. Foss. Corals, p. 1xx. SYNAPTOPHYLLUM (Simpson) Simpson, Bull. 39, New York State Museum, Vol. VIII, p. 212, Figs. 33, 34, 35, 36; 37.
V DIELGORAE
The opinion is gaining some currency in geological circles that the official geological surveys, national and state, are likely to become, at no distant day, little more than economic bureaus administered for their immediate serviceability to industrial enterprises. It is even apprehended that they may drift so far in this direction that they will fall short of being, in the highest, broadest, and truest sense, economic, since this involves the development of the deeper scientific values which are the foundation of the sounder economics.
Running as the mate to this forecast is the complementary proph- ecy that the evolution of geological science and of its educational economics will be relegated essentially to the universities.
It must be acknowledged that there is some ground in current drift for these twin forecasts. If it were possible to find an abso- lutely impartial and thoroughly competent jury to pass upon the work of the past decade, its verdict would possibly be that the larger and more far-reaching contributions to the science of geology have come from the universities, and that their relative productive- ness in this field has been markedly increasing. It might even be decided that the most valuable contributions to the working methods of the science, especially those of the more searching and refined class, have also come from the universities. At the same time it would doubtless be decided that the economic efficiency of the gov- ernmental surveys has been notably increased and the adaptability of their results to immediate commercial demands has been markedly enhanced. Very likely a perfectly impartial judge, surveying criti- cally the appropriate function of the official surveys, on the one hand, and of the universities, on the other, would give his approval to some notable divergence of effort along the lines that have thus been realized in recent practice, if it were controlled by appropriate limita- tions. At the same time he would doubtless recognize that no small restraint upon excessive tendencies in either direction is quite essential to the permanent success of the surveys, if not also of the
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universities. If the surveys become narrowly economic and concern themselves chiefly with conventional descriptions and mappings, interpreted along inherited lines, without the inspiration and regen- erative influence of profound investigation, it is not difficult to foresee that in a very short period their products would fall so far below those of the progressive geologists who are engaged in advancing the science that discredit would be brought upon the surveys and their overthrow or reorganization invited. The ultimate good standing of official work is intimately dependent upon a constant revision of basal ideas and a persistent improvement of methods founded upon an ever-increasing command of the fundamental principles that underlie the science, and stimulated by a perpetual search for more complete knowledge. This is as true of the economic phases of the science as of any other. Besides this, it is impossible to foresee accurately what may and what may not come to have economic value. It may be predicted with much confidence that not a few new aspects of the science whose economic relations are as yet wholly unrecognized will prove to be among the most valuable contributions to the broader and deeper economics of the future.
If the universities were supplied with the requisite means, they might be disposed to accept complacently the foreshadowed alter- native assigned them. To come into an essential monopoly of the immeasurable riches that lie scarcely concealed beneath the surface of existing geological science might well be regarded by them, from the narrow point of view, as a boon to be welcomed with ardor. To be thus -left free to rework the relatively raw results of surveys made for immediate industrial ends, and to bring forth from them by supplementary inquiry their true scientific riches, might, speaking again narrowly, be a source of great seeming advantage to the uni- versities. The universities, however, are not now supplied with adequate means for cultivating this great field. They are gaining these rapidly, and might doubtless attain them at an early day, if so inviting a field is to be thus measurably vacated for them.
But, from the higher point of view, it seems clear that any sharp differentiation of the kind foreshadowed, if it were permitted to go beyond the most moderate and restrained limits, would be injurious to the sum-total of results, and to the larger interests of both univer-
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sities and surveys. That it would be little less than fatal to the official surveys, in the long run, is scarcely to be questioned, as they and their results would fall into disrepute unless constantly fed by new science, new methods, and new men broadly and thoroughly equipped. That it would be unwholesome for the universities to be dissevered from industrial work for the common good and to be out of sympathy with official surveys is scarcely less obvious. The higher interests of the surveys and the universities alike will be conserved by a harmoni- ous co-operation in which both shall strive to reach at once scientific and economic results. Differences in the relative stresses and pro- portions of immediate effort, in the one direction or the other, are obviously appropriate and laudable; but no university can wisely neglect the useful side of the science it cultivates, nor can any official organization, without jeopardy, ignore the profounder scientific aspects of the field it cultivates.
But, above all, intellectual economics should not escape recogni- tion. The intellectual wealth of the nation is its greatest wealth. The contribution which intellectuality has made to the present mate- rial prosperity, even if we weigh nothing higher, is perhaps its greatest contribution. Large as are our native resources, they would yield a relatively small return to our people, were it not for that acute mental activity, that signal intellectual power, and that abounding sagacity which so distinctly characterize the present industrial evolu- tion. This intellectuality lies not so much in the mere possession of technical knowledge as of insight, constructive genius, and aggres- sive mental energy; and these are fostered more effectually perhaps by the influence of independent original research, by the modes of thought and the spirit of investigation, than by any other single agency.
By as much as these intellectual possessions are our greatest assets, by so much would a failure to promote them in the most effective manner be the greatest of economic shortcomings, whether on the part of an official organization or of a university.
Ce:
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Geodetic Operations in the United States 1903-1906. A Report to the Fifteenth General Conference of the International Geodetic Association. By O. H. Tirrmann and J. H. Havrorp. Washington, 1906. Pp. 45.
While this paper embraces, as indicated, a statement of the principal operations of the Coast and Geodetic Survey for 1903-6, its chief contri- bution zelates to the figure of the earth. The part of special interest to geologists is that which deals with the relation of variations of density in the outer part of the lithosphere to the great surface reliefs. The investigation bearing upon this point was based wholly on the deflections of the vertical, no use being made of determinations of force of gravity. The area treated extends over 18° 51’ in latitude and 50° 7’ in longitude. Astronomic determinations of the deflection of the vertical to the number of 507, all connected by continuous primary triangulation, were used.
It has long been known that the force of gravity on the surface of the earth is not distributed as though the sub-surface material were either homogeneous, gravitatively, or symmetrical. The investigation set forth in this paper, while fully confirming this, goes much beyond any previous inquiry in determining the nature of the inequalities in the distribution of gravity and their correlation with topography. It thus constitutes a very notable advance in this important line of research. The deflections of the vertical that are assignable to variations in the topography, con- sidered by itself alone, were first determined in a very comprehensive way, the effect of the reliefs within a radius of 4126.4 kilometers being computed for each station. The results clearly indicated that the material of the protuberances, viewed largely, has less inherent gravity than that of the basins—a conclusion in accord with the general tenor of previous inquiries in different periods of the world. It remained therefore to deter- mine the distribution of the internal inequalities of density thus disclosed.
The essential feature of the problem was to find out whether the differ- ences of density are so distributed that the continental and oceanic columns balance one another or not, and, if they do, at what depth the equation is established. A series of hypotheses relative to this were adopted as the bases of trial solutions. While these hypotheses, so far as they enter
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into the real inquiry, related solely to the distribution of gravity, they have been associated by the authors with ideas of rigidity and isostasy, the purpose of this undoubtedly being to give to the inquiry a definite relation to geophysical problems. While this purpose is eminently laud- able, it is not clear to the reviewer that this particular association with questions of rigidity and isostasy is altogether happy, as will be indicated later. These terms will therefore be omitted from the following state- ment of the hypotheses on which the trial solutions were based, though the term ‘‘isostatic compensation”? will be retained as a convenient expres- sion of gravitative equilibrium reached by variation in density.
Five trial solutions by the method of the least squares were made on the basis of five hypotheses of the distribution of density, as follows:
Solution A was based on the assumption that there is a complete isostatic compensation at the depth zero beneath the ocean floor; that there exists immediately below every elevation a defect of density fully compensating for the elevation, and that at the very surface of the ocean floor there lies material of the excessive density necessary to compensate for the depres- sion of this floor.
Solution B was made on the assumption that the portions of the con- tinent above the sea-level are excesses of mass, and that the oceans repre- sent deficiencies of mass, and that no isostatic compensation exists; or, in other words, the solution was based upon the supposition that, if iso- static compensation exists, it is uniformly distributed through an indefinite depth.
Solution E was made on the assumption that isostatic compensation is complete and uniformly distributed throughout a depth of 162.2 kilo- meters.
Solutions H and G were of the same type as E, but based on the assumptions that the depths of compensation are 120.9 and 113.7 kilometers respectively.
The sums of the squares of the residuals of these different solutions were as follows:
Solution A, depth of compensation zero) 52". nee) 2 13,937, Solution B, depth of compensation infinity . . . . . . 65,104 Solution E, depth of compensation 162.2 kilometers . . . 8,174 Solution H, depth of compensation 1207 Oukilometers eae) 67,087, Solution G, depth of compensation 113.7 kilometers . . .. 7,983
It is to be noted that in Solutions E, H, and G the density compensa- tion is assumed to be uniformly distributed to the depths named measured from the varying surface of the lithosphere. Of these solutions, G, having
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the smallest sum of the squares of the residuals, is regarded as the closest approximation to the truth.
It thus appears that the inferior densities and greater protuberances of the continental reliefs are such that their joint gravitative effects are balanced by the greater densities and negative protuberances of the oceanic basins at a depth of about 114 kilometers, or 71 miles, if the deficiencies and excesses of density respectively remain uniform to this depth. It was not found possible, however, to determine, from the observations on the deflection of the vertical now available in the United States, whether this or some other was the actual mode of distribution of the compensating densities. The authors recognize, as a possible alternative, a distribution in which the compensating differences of density are greatest at the sur- face and decline uniformly to a vanishing point, which would be reached at a depth of about 109 miles. ‘The authors speak of the former mode of distribution as more probable than the latter, but whether this is based upon considerations growing out of the reduction of the observations or upon geophysical views is not indicated. From the geological point of view, it seems to the reviewer that a decline in differences of density from the surface to a vanishing point is much more probable than uniform differences ceasing suddenly at a given horizon. It seems, furthermore, that a varying decline from a maximum near the surface to a vanishing point in depth is more probable than either. Especially does it appear probable that a vanishing differentiation below represents the true con- dition when account is taken of the great depth to which the compensating densities reach as disclosed by this investigation.
A vanishing differentiation of density, rather than a uniform one ceasing abruptly, would seem to be probable under any recognized hypoth- esis of the origin and mode of formation of the earth that is built upon consistent and plausible grounds. None of the older current hypotheses respecting the mode of formation of the earth, so far as we know, postulates a lateral differentiation of densities at so great a depth as 70 to too miles; but if these hypotheses are modified so as to be brought into conformity with these new determinations in the matter of depth, it would seem that, to be consistent with the conditions of the case, they must, in all probability, involve increasing horizontal differentiations from the lowest horizon at which these were developed to the surface, and that these would most probably have a differentially varying value.
The theory of accretion from planetesimals is perhaps the only one which has definitely postulated a horizontal differentiation of densities at horizons of so great depth. It specifically assigns to the continental and
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oceanic sectors differences of specific gravity reaching to these and greater depths, and attributes them to differential weathering supposed to have
A A A A B Cc FIG. I
BC
begun at a relatively early stage in the growth of the earth, and to have increased upward at more than a simple ratio until the surface was reached. The effects of the original differentiation by weathering are sup- posed to have been subsequently modified by vulcanism in such a way that the lighter portions of the differen- tiated material were brought to or toward the surface in larger percentage than the heavier material, the effect of which was to concentrate the differences of density previously developed toward the surface. The final differentiations of density thus postulated would there- fore be greatest at the surface, and would decline down- ward at a varying rate, whose nature may be roughly indicated by the curve C-C in Fig. 1, where it may be compared with the rectangle AAA and with the triangle ABB which represent the two modes of compensatory distribution referred to above. So far as the reviewer can judge from an inspection of the data furnished by the paper, a distribution of densities such as is repre- sented by the curve C—C would satisfy the requirements of the observations as well as either of the others. It would seem, therefore, to be a matter of some felicity that the accretion hypothesis should have assigned, on its own grounds and as the inevitable result of the processes it postulates, a specific differentiation and distribution of densities in fairly close accord with these new determinations based on wholly independent con- siderations. *
The authors speak of Solution B as being based on the supposition that the earth is rigid, and of Solutions E, G, and H as though they represent isostasy. They say that the investigation ‘‘/eads to a definite and positive conclusion as to rigidity versus tsostasy.”’? They add:
For the United States and adjacent areas, the assumption
of extreme rigidity is far from the truth. On the contrary, the assumption that the earth is in the condition called isostasy is a comparatively close approxima-
t Chamberlin and Salisbury, Geology, Vol. I], pp. 107-11.
2 P. 10; italics theirs.
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tion to the truth. In other words the United States is not maintained in its position above sea-level by the rigidity of the earth, but is, in the main, buoyed up, floated, because it is composed of material of deficient density.*
So far as the reviewer can see, that which is really determined does not extend beyond the distribution of density, and all that is added to this is inference or interpretation. It is therefore consistent with the very highest appreciation of the value of the determinations to question the validity of these superimposed interpretations.
The authors are probably entirely correct in assuming that the distri- bution of specific gravities postulated in Solution B could not be maintained without great rigidity in the deeper portion of the earth. It is equally beyond the probabilities that such a distribution of matter could ever have arisen under any tenable hypothesis of the mode of the earth’s forma- tion. But, while the maintenance of this unrealizable condition of things is excluded by the investigation, it is not apparent that it excludes rigidity under more tenable conceptions of the formation of the earth. The exclu- sion of an extreme and indefensible hypothesis does not logically cover all other hypotheses. It is possible that the authors did not really intend to convey the impression that the conceptions of rigidity held by certain physicists and geologists were incompatible with their determinations, but their language seems to imply this.
So, on the other hand, when the authors say ‘‘The United States is not maintained in its position above sea-level by the rigidity of the earth, but is, in the main, buoyed up, floated, because it is composed of material of deficient density,”’ their language carries the impression of a positive affirmation of liquidity or viscousness at the base of the crust in which the differentiated densities reside. Such is the usual conception that goes with the term “‘isostasy”’ as it has been used in geological literature. Now, that which is really demonstrated in this important investigation is simply that the compensation of densities becomes approximately complete some- where between 50 and 150 miles below the surface. The agencies which have produced this differentiation of densities and the physical conditions which now maintain it do not seem to be really touched by the investi- gation, but to be matters of inference or interpretation based upon other considerations. In the judgment of the reviewer, this differentiation may have arisen and may be now maintained without involving any nearer approach to fluidity than that which is manifested by bodies whose rigid- ities range from the best granite to the best steel and beyond. Deforma- tions by molecular transfers from crystal to crystal without essentially
TERT Os
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affecting the state of rigidity ought now to be regarded as at least a plausible, if not an established, geophysical process, as urged by Van Hise and others in relation to the so-called flowage of crystalline rock, and by Chamberlin and others in relation to the so-called flowage of glaciers. A condition of gravitative balance essentially equivalent to that arising from isostatic flotation may thus be reached in great masses of matter which are at every instant and in all parts affected by a high degree of rigidity. Under this conception the protuberant area of the United States may be supported by a base which is rigid in the truest sense of the term. In this case it could be said to float on its base in no more appropriate sense than the Greenland ice-fields may be said to float on their rock bottom.
There is a specific objection to entertaining the conception of a crust of 70 or 100 miles floating on a mobile substratum. A crust of that thick- ness, if formed of the firmest granite, would still have but a limited power of accumulating lateral stresses, and hence must yield to such stresses as fast as they reach a moderate magnitude and give rise to practically con- tinuous folding. It is, however, quite certain that most mountain foldings took place in relatively short periods. We seem therefore to be shut up to the alternative of supposing either that the agencies which produced mountain foldings came into play for short periods only and then ceased, or that the body of the earth is capable of accumulating stresses for a long period until, having attained large magnitude, they reach the limits of resistance and deformation ensues in a comparatively short period- The former hypothesis does not seem to the reviewer to have been assigned a competent basis and a working method, while the latter appears to find such a basis in the pervasive rigidity of the outer half of the earth implied by various astronomical and physical data, provided depths of several hundred miles, affected by high rigidities throughout, are assumed to act in strict co-ordination in withstanding deformation during the period of stress accumulation. ‘There are, therefore, serious grounds for hesitating to accept conclusions involving fluidal or viscous mobility beneath a shallow sub-crust, unless the evidence is direct and specific.
If that portion of the paper which relates to rigidity and isostasy be put into the category of inferential and interpretative matter, to which there are at least recognized, if not plausible, alternatives, the positive determinations, standing as they seem to do on a firm basis, may well be regarded as constituting a contribution of the first order of importance.
Mace:
To anticipate any misapprehension that might have crept into the foregoing review or that might grow out of it, the manuscript was submitted to the authors of
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the paper with an invitation to suggest points of revision or to add a statement to go with it. In response to this, the following comments have been prepared by Mr. Hayford. In the light of these, the review might well be modified at some points, but to avoid disturbing the basis of Mr. Hayford’s comments it is left precisely as submitted:—T. €- C:
COMMENT ON THE ABOVE REVIEW BY MR. JOHN F. HAYFORD
The Report reviewed on the preceding pages by Professor Chamberlin, is essentially a preliminary statement. It was necessarily short, being one of many presented by various countries to the International Geodetic Association for publication in its triennial report. Another short pre- liminary statement in regard to the same investigation is also available in print, in the Proceedings of the Washington Academy of Sciences. Both of these statements are subject to defects due to brevity. So, also, must the statement here made be brief and defective. It is hoped that a much more complete statement of the investigation may be published by the Coast and Geodetic Survey within a year from date.
The fair and clear review by Professor Chamberlin is welcomed by the undersigned. A few statements seem to be necessary, in justice to the geodetic investigation under discussion, in order that there may be no misunderstanding. :
Professor Chamberlin’s distinction between demonstration and inter- pretation, in connection with this investigation, is correct. _The investi- gation demonstrates that the present distribution of densities follows a certain law. The statement of the meaning of this law in terms of rigidity is interpretation, and this interpretation depends, in part, on considera- tions outside the scope of the geodetic investigation. It seems to the writer, however, that the interpretation, given in terms of rigidity, is reasonably safe. When the interrelations of the geodetic and geologic evidence are more fully appreciated than at present, it is believed that others will reach the same conclusion.
Before discussing isostasy, it is necessary to get a clear conception of what the word means. It is stated in the review that certain language in the Report ‘carries the impression of a positive affirmation of liquidity or viscousness at the base of the crust in which the differentiated densities reside. Such is the usual conception that goes with the term ‘isostasy,’
t John F, Hayford, C.E., “The Geodetic Evidence of Isostasy, with a Considera- tion of the Depth and Completeness of the Isostatic Compensation and of the Bearing of the Evidence upon Some of the Greater Problems of Geology,”’ Proc. Wash. Acad. Sci., Vol. VIII, pp. 25-40 (May, 1906). The writer will be glad to furnish copies of this paper to interested persons.
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as it has been used in geological literature.”” The language used in the Report was not intended to give the impression stated in the words just quoted. The writer, being aware that the word ‘“‘isostasy’”’ has been frequently misunderstood and used inaccurately, carefully defined it at considerable length in both his preliminary statements before the Wash- ington Academy and the Geodetic Association. The idea of a crust composed of relatively rigid material, floating upon a liquid or viscous substratum, is not necessarily implied in these definitions. Nor is it necessarily implied in the original definition of isostasy by Dutton.t The floating crust represents one possible method of isostatic adjustment. Dutton does not believe in a floating crust, nor does the writer. The geodetic investigation under discussion contains strong evidence, not set forth fully in either preliminary statement because of lack of space, which is against the crust hypothesis. The condition of approximate equilibrium called isostasy may exist in materials in which there are no sudden changes in viscosity.
In his review Professor Chamberlin states that, under the accretion hypothesis, an initial arrangement of densities might be produced such that the condition of approximate equilibrium called isostasy would exist, and that therefore the present existence of isostasy does not necessarily prove any- thing in regard to the rigidity or lack of rigidity of the earth. The follow- ing quotation? shows that the writer recognizes that such an initial con- dition may have existed, but that he also recognizes that, even if it did exist, the present facts still constitute a proof of low rigidity and of iso- static readjustment:
It is possible that the continents and oceans are in their present positions because light materials accumulated at the outset in the places now occupied by the continents, and heavier material accumulated where the deep oceans now lie. This would constitute an initial isostatic adjustment. But the geologic evidence is overwhelming that within the interval covered by the geologic record many thousands of feet of thickness have been eroded from some parts of the earth, and have been transported to and deposited upon other parts. If isostatic readjustment had not also been in progress during this interval, it would be impossible for the isostatic compensation to be so nearly complete as it is at present.
The writer believes the degree of completeness of the isostatic adjust- ment to be a measure of the degree of effective rigidity, under forces con-
1 C. E. Dutton, ‘On Some of the Greater Problems of Physical Geology,” Bul- letin of the Philosophical Society of Washington, Vol. XI, p. 53.
2 Hayford, The Geodetic Evidence of Isostasy, p. 35.
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tinuously applied for a long time, of the material composing the outer part of the earth. A flowage of rocks, of the character referred to in Professor Chamberlin’s review, may be one of the ways in which the material yields to forces continuously applied for a long time, even though those forces are not sufficiently great to produce motion if applied for a short time only.
Professor Chamberlin has, in the curve C—C, furnished a statement of the manner of distribution of the isostatic compensation with respect to depth corresponding to the accretion hypothesis. Since writing this review, Professor Chamberlin has been assured that a sub-solution upon that basis will be added to the geodetic investigation before the final publi- cation is made.
Joun F. Hayrorp
Inspector of Geodetic Work Chief of Computing Division, Coast and Geodetic Survey
The Geology of South Africa. By F. H. Hatcu and G. S. CorRstRo- PHINE. London and New York: The Macmillan Co., 1905. Pp. 348, 2 maps, 89 figures.
The authors have attempted in this work to put within the limits of a small volume the essentials of the geology of South Africa. Their long experience in South African geology, both in the Transvaal and Cape Colony, has fitted them well for their task. The literature of South African geology is especially burdened with a great mass of semi-scientific writings which deal with isolated areas, without any attempt at correla- tion with neighboring regions, and only recently by the work of the Cape Colony and Transvaal surveys, has geological work been carried to a stage that would warrant the treatment of South Africa as a unit. The book contains some details that were hardly intended for the student so far away as America, and, on the other hand, many general points of vital interest are passed over all too briefly. This is especially true of the physical history and dynamical problems of the region. Nevertheless, the volume is a valuable and welcome summary of the geology of this distant land.
The “pre-Karroo” (pre-Permo-Carboniferous) rocks are treated in two sections: Section I describes those of south Cape Colony; Section II those of the Transvaal and neighboring regions. At the base, in both regions, is a series of micaceous slates and quartzites with occasional conglomerates and crystalline limestones, into which were intruded granite
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masses, causing considerable metamorphism, and resulting in a great variety of schists. ‘This series is classed as Archean.
The great group of rocks resting unconformably on the Archean, and below the Cape System (the upper part of the pre-Karroo group), has not yet been correlated with the formations of other countries. ‘They consist of slates, quartzites, grits, conglomerates, and dolomites. In the Transvaal the group has a thickness of 35,000-40,000 feet, and includes three unconformable systems; the lower one of which, the Witwatersrand,. consists of twelve formations and has a thickness of 20,000 feet. ‘The conglomerate beds of the Witwatersrand contain valuable gold deposits, having an output, in 1904, of about $70,000,000. ‘The second system of the group is largely volcanic; the third is made up of clastics and dolo- mites.
The Cape system consists in its best development (south Cape Colony) of three conformable series of slates, quartzites, shales, and sandstones. The middle series, the Bokkeveld, contains the oldest recognizable fossils found in South Africa. ‘They are of Devonian age.
The ‘‘Karroo system” is a conformable series beginning with Permo- Carboniferous strata, and extending to the end of the Triassic. The system has a thickness of about 20,000 feet, and is composed of sand- stones, shales, and conglomerates. It outcrops in an elliptical north- east-to-southwest area covering three-fourths of South Africa. In south Cape Colony it rests conformably upon the Cape system, but elsewhere it is unconformable on older rocks. At the base of the system is the Dwyka glacial conglomerate of Permian age.
The ‘Coastal system’? (Cretaceous) consists of two series occurring in different regions; one is of Lower, the other of Upper Cretaceous age.
Post-Cretaceous beds are represented by superficial deposits, usually cemented, which probably range from Tertiary to quite recent, but in the absence of fossils they are not classified.
The igneous rocks of known age are discussed along with the sedi- mentary series and chap. 1 of Part IV treats some volcanic rocks of doubtful stratigraphical position.
Chap. ii of Part IV is devoted to the occurrence and origin of the diamond bearing deposits.
In Part V the authors discuss the correlations of the strata of the various regions of South Africa and their position in the geological column. The correlation tables here and in other parts of the book are especially valuable.
The chief subdivisions are here reproduced.
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CORRELATION TABLE OF SOUTH AFRICAN STRATA
European Southern Northern : Equivalents Cape Colony Cape Colony Natal Transvaal Superficial Deposits | Superficial Deposits | Superficial Deposits | Superficial Deposits Umtamvuna Umtam- Series , vuna Cretaceous.. coast Coastal Series ¥ Uitenhage y Series Rhaetic.... Stormberg Stormberg Series Series Karroo ) Beaufort Karroo Karroo ) Beaufort | Karroo System Series | System System Series | System Permo-Car- Ecca Ecca Ecca Ecca boniferous. Series Series Series Series Devonian ..| Cape System Cape System Cape System Waterberg System Congo System Griqualand System Potchefstroom x System Tbiquas? Amygdaloids of Ventersdorp the Vaal River System Witwatersrand System Archean ....| Malmesburg System Namaqualand Swaziland System Swaziland System ystem
iene:
New York State Museum, Bulletin 99. Quadrangle. By D. D. LUTHER, map.
Geologic Map of the Buffalo 1906. Pp. 29 and geologic
This bulletin is the latest one, prepared under the direction of Dr. John M. Clarke and published by the New York State Museum, devoted to the mapping and description of the geologic formations of a quadrangle. As is customary with this series of bulletins, it contains a map on which the areal distribution of the various formations is shown, accompanied by a text giving an account of their occurrence and characters together with lists of their common and diagnostic fossils. As stated by Dr. Clarke, “students of geology in Buffalo will find the map and its accompanying text a detailed guide to the rock sections of the region and to the scattered and often obscure outcrops of the formations, and, since this is the second largest city in the state, the bulletin will be of special service to a large number of people.
The strata composing the surface rocks of this quadrangle have an aggregate thickness of over 800 feet and are of Devonian age, with the
84 REVIEWS
exception of the Salina beds and Cobleskill waterlime which are in the Upper Silurian. From an economic standpoint the Bertie waterlime at the top of the Salina beds is the most important division of the Silurian rocks, since it is extensively quarried in North Buffalo and Williamsville for the production of natural cement. Paleontologically, the Bertie water- lime is characterized by an “abundant and peculiar crustacean fauna’’ of lobster-like forms belonging in the extinct orders of Eurypterida and Phyllocarida. ‘The highest bed of the Upper Silurian in the Buffalo region, in somewhat earlier papers, had been referred either to the Onondaga or Manlius limestones, but recently has been correctly correlated by Hart- nagel with the Cobleskill limestone (formerly Coralline) of eastern New York. The Rondout waterlime and Manlius limestone of the Upper Silurian and the Helderbergian limestones of the Paleo-Devonian do not reach western New York, so that the oldest Devonian rocks rest unconformably by erosion upon the Cobleskill waterlime. The quartz sand filling the fissures in the Cobleskill waterlime, which infrequently extend down into the Bertie, is considered Oriskany sediment and, consequently, the oldest Devonian deposit. The oldest well-represented Devonian formation is the Onondaga limestone, with a thickness of about 160 feet, which is quar- ried extensively for building-stone and the production of quicklime. This limestone contains a considerable amount of carbonaceous matter, nodular layers of chert, and large numbers of fossils.
The Onondaga limestone is followed by the Marcellus beds which are divided into the Marcellus black shale, representing the typical shales occurring at Marcellus, the Stafford limestone, and the Cardiff shale. The Hamilton beds are well shown at various localities on the southern part of the quadrangle and are divided in ascending order into the Skaneateles and Ludlowville shales, Tichenor limestone, and Moscow shale. Fossils are abundant in all of these divisions, with the exception of the lowest one— the Skaneateles shale. The Hamilton beds are succeeded by the Genesee beds of which the typical Genesee black shale is practically absent. The Genundewah limestone, an irregular concretionary stratum, I to 2 feet thick, and the West River shale, about 12 feet in thickness, are well shown. The limestone in many places is composed largely of the shells of the minute Pteropod, Styliolina fissurella, and, on that account, has also been called the Styliola limestone. The Portage beds are the youngest ones described and on this quadrangle the subdivisions of the Middlesex black shale, the Cashaqua shale, and the Rhinestreet black shale occur. The two black shales of the Portage contain comparatively few fossils; but they are fairly common in the Cashaqua shale and its interbedded calcareous, concretionary layers. CSc
REVIEWS 85
PERIDOTITES AND CORUNDUM [AUTHOR’S ABSTRACT]
Corundum and the Basic Magnesian Rocks oj Western North Caro- lina. By J. Votney Lewis. Bulletin, North Carolina Geologi- cal Survey, No. 11, 1896.
Corundum and the Peridotites of Western North Carolina, By JosEpH HyprE Pratt and JosepH VoLNEyY Lewis. Reports, North Carolina Geological Survey, Vol. I, 1906.
Corundum and its Occurrence and Distribution in the United States. By JosrepH Hyper Pratt. Bulletin, U. S. Geological Survey No. 269, 1906.
Although a decade elapsed between the appearance of the first and the last two of the above publications they are so intimately connected that they should be reviewed together.
The first is a record of the distribution and the modes of occurrence of the peridotites and the associated corundum deposits of western North Carolina, with briefer descriptions of similar occurrences throughout the eastern crystalline belt of the continent.
The second is an elaboration and revision of the first, particularly as regards the petrography of the peridotites and the mineralogy of corundum and the associated minerals. It differs essentially from this, however, in that it takes up quite fully the theoretical questions of origin and relation- ships of the various rocks and minerals concerned.
The third publication listed above, although bearing the name of but one of the authors, is essentially a rearrangement of the subject-matter of the other two, with the omission of most of the petrography and a slight enlargement upon important localities outside of North Carolina. It is, in the main, a reprint, both in text and illustrations, although this fact is nowhere indicated. A footnote on p. 28 merely refers to the North Caro- lina report, without naming the authors or intimating that the text is the same. Joint authorship for four pages of text is acknowledged, however, in a footnote on p. 62, and the reader is left to infer that the remainder is the work of the author whose name appears on the title-page.
This review is therefore chiefly concerned with the second, Corundum and the Peridotites of Western North Carolina, which constitutes the first volume of a new series of reports of the North Carolina Geological Survey. It is a volume of 464 pages, is illustrated by 45 plates and 35 figures in the
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text, and is in many respects a work of much broader scope than the title indicates.
As stated in the preface, the petrography was chiefly the work of Lewis, and the mineralogy was in charge of Pratt. Other portions of the work are the result of collaboration, and there was a constant interchange of all manuscript for criticism and revision. The individual work of the authors was done, for the most part, at different times and places, each working independently. Notwithstanding this fact, each was led to essen- tially the same conclusions in regard to the origin and relations of both the peridotites and corundum. Concerning corundum in the basic magne- sian rocks, very similar, and in some respects supplementary, hypotheses were deduced by the one from a study of the mines in the peridotites and by the other from the petrology of the corundum-bearing amphibolites and anorthosites. (Cf. pp. 144 and 344.)
A brief sketch of the geology of the state is given in chapter i, with a somewhat fuller account of the belt of gneisses, granites, and schists con- stituting the rugged mountainous section in which the peridotites and the corundum deposits occur.
Chapter ii deals with the peridotites and the associated basic magne- sian rocks. ‘These include four varieties of peridotite, four pyroxenites, four gabbroic rocks, an amphibolite, and three diorites. These are chiefly well-known types. An exception is the pyroxenite composed of the ortho- rhombic pyroxene, enstatite. This rock occurs somewhat commonly throughout the region, and forms many masses of considerable extent. The name enstatolite is proposed for this type, in conformity with the terms “‘bronzitite” and ‘‘hypersthenite.” All of these rocks are shown to be a part of the great series of basic magnesian rocks which extends through- out the whole length of the eastern crystalline belt from central Alabama to the Maritime Provinces of Quebec, and again reappears in Newfound- land. ‘Together they constitute a petrologic unit of remarkable persist- ence and uniformity of characters and association.
Maps show the distribution and relations of these rocks to the crystal- lines in eastern North America and in western North Carolina, besides several detailed maps of portions of the belt of particular interest. The contoured geological map of western North Carolina (Plate II) is the largest and most detailed yet published of this region. The scale is eight miles to the inch and the base is printed in three colors. On this the pre- Cambrian gneisses and schists and the Cambrian (?) metamorphic sedi- ments are represented by tints, while the peridotite dikes and localities of corundum, chromite, and asbestos are shown in bright red.
REVIEWS 87
Following the descriptions of these rocks throughout the Appalachian region, the distribution and petrographic characters are given in detail for western North Carolina. Sixty photomicrographs illustrate the mineral- ogic and structural varieties and modes of alteration of the rocks described, and their chemical relations are shown by Hobbs-Broégger diagrams.
Two classes of secondary rocks are described: namely, (1) the mechanic- ally derived schists, gneisses, and gabbrodiorites, and (2) a series of hydrous alteration products, chiefly steatite, chloritite (chlorite-rock), and serpen- tine.
The vast majority of occurrences, while more or less altered, are essen- tially fresh primary rocks. This is especially true of the pure olivine- rock, dunite, which is the most common type. Steatite and chloritite are pretty widely found, but serpentine is practically confined to a region within fifteen miles of the French Broad River. Even here remnants of unaltered peridotite are abundant.
The various modes of alteration and decomposition are described in chapter iv. Five distinct processes are recognized, and are designated, except the first, by the prevailing product; namely, (1) weathering, (2) serpentinization, (3) steatitization, (4) chloritization, (5) amphibolization. All of these processes occur more or less together over wide areas, but one or another usually greatly predominates. Hence various areas are char- acterized by ocherous weathering products or by the abundance of one of the minerals, serpentine, talc, chlorite, and amphibole, with smaller proportions of the others.
The long-vexed question of the origin of the peridotites is discussed in chapter v. A historical sketch shows the kaleidoscopic variety of opinions and hypotheses that have been advanced to account for these rocks since 1875, the date of Professor Kerr’s first report on this region. By various authors they have been regarded as unaltered sediments, metamorphic sediments, chemical deposits, metasomatized limestones and schists, and as igneous intrusions. Opinions have been divided chiefly, however, into. two groups, corresponding closely to the old Neptunian and Plutonic schools of geology. The strong modern tendency toward the igneous. theory of origin is clearly shown, and the correctness of this view is abun- dantly substantiated by this report. The data presented on this point are grouped under five heads, as follows: (1) mineralogic characters, (2) microscopic characters, (3) gross structures, (4) modes of occurrence, (5) relations to the gneisses and schists.
In the discussion of the general petrology of the basic magnesian rocks, the genetic unity of the series throughout the eastern crystalline belt is.
88 REVIEWS
strongly emphasized. It is noteworthy that a closely similar association of rock types is found in almost every peridotite locality, although some one usually preponderates in every case. Thus peridotites, particularly dunite, prevail in North Carolina and Quebec, pyroxenites in Pennsyl- vania, while gabbros are abundant in Delaware and parts of Maryland. The types represented in the various regions, however, are almost identical, and the petrology is closely similar, except in the relative abundance of the various types and in mode and degree of alteration.
Two generations of corundum are recognized. The greater part, including all deposits of commercial value, belongs to the first generation and represents the excess of alumina in the original magma. Another part, occurring in microscopic grains, is an excess of alumina arising from the corrosion of anorthite crystals by the still molten magma. This pro- cess has produced sheaths of minerals which form the corrosion mantles, so greatly developed in some localities, and in other cases entirely replacing the anorthite, or the corroding magma, as the case may be, by nestlike aggregates of intermediate silicates.
In discussing the age of the peridotites (pp. 152-59), it is recalled that until recently it has been the custom of geologists to refer the whole of the Appalachian crystalline belt to the Archaean, or at least to pre-Cambrian. Recent work in several regions makes it impossible longer to accept these old correlations without other than merely lithologic evidence. ‘Tables are given showing possible correlations of the crystallines in areas recently investigated, from North Carolina to Massachusetts and the Green Moun- tains, and summaries are given of the various conclusions as to age arrived at by geologists in different parts of the field. The conclusions of the authors of this report may be briefly stated as follows: The intrusion of the peridotites was probably contemporaneous, or practically so, for the whole region under consideration, from Alabama to Newfoundland. These rocks now form a belt of remarkable unity through a region of great oro- genic disturbance and intense metamorphism. ‘These facts, together with the geologic relations that have been deciphered in some northern portions of the belt, suggest the hypothesis that the chief period of intrusion may be correlated with the folding movements of closing Ordovician. The peridotite belt doubtless marks the axis of most intense disturbance. The later orogenic movements, at the close of the Carboniferous, produced the widespread lamination of these rocks, and probably gave occasion for additional minor intrusions. Much painstaking work yet remains to be done, however, in many parts of the field, before any hypothesis concerning the age of the peridotites can be satisfactorily established.
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Chapter v closes with a discussion of the secondary rocks. ‘The authors undertake to trace back to their original types the various laminated and hydrated derivatives. The question arises whether the amphibolites, diorites, hornblende-schists, and hornblende-gneisses, may not themselves have been derived from corresponding pyroxenic types, such as occur in the Maryland and Delaware gabbro areas. The fact that undoubted gabbrodiorites do occur in portions of the belt in North Carolina makes it quite probable that many, if not all, of these amphiboliferous types have had a like origin.
Chapter vi deals with the mineralogy and technology of corundum, including its crystallography, its physical and chemical properties, its applications in the arts, and an outline of the process of manufacture of the several types of corundum and emery wheels on the market.
Chapter vii, on modes of occurrence, shows corundum to be a constit- uent of a remarkable number and variety of rocks, including nineteen igneous types, nine metamorphic, and one unaltered sedimentary. These corundum-bearing rocks are distributed as follows:
CORUNDUM-BEARING IGNEOUS ROCKS
North Carolina Other American Localities Elsewhere Peridotite Granite Kyschtymite Pyroxenite Syenite Diorite Amphibolite Nephelite-syenite Tonalite Anorthosite Plumasite Gabbro Pegmatite Norite Trachyte
Andesite Quartz-porphyry
Monchiquite Basalt
CORUNDUM-BEARING METAMORPHIC ROCKS
Serpentine Crystalline limestone Corundum-schist Gneiss Corundum-porphyroid Mica-schist Graphite Quartz-schist Igneous contacts Amphibole-schist Inclusions Chlorite-schist
OTHER CORUNDUM-BEARING ROCKS
Alluvial gravels Undetermined (emery)
The American occurrences, particularly those of North Carolina, are described in detail and compared with similar deposits, when known, in other parts of the world. Those of chief commercial importance in North Carolina are in peridotites, and to a less extent in amphibolites and pyroxenites. The gravel deposits are of interest on account of the corun- dum gems (rubies) and the garnet gems (rhodolite) that occur in some of them.
In peridotites corundum occurs chiefly (1) in peripheral or border
go REVIEWS
“veins” which skirt along the borders of many of the massive outcrops, and (2) in interior ‘ extending from the borders toward the center of the peridotite mass. The mode is similar in the pyroxenites and in certain amphibolites. In other amphibolites, the corundum is irregularly disseminated in grains, plates, and nodular aggregates throughout large masses of the rock. Corundiferous pegmatite forms small dikes accom- panying and penetrating both peridotites and amphibolites in some locali- ties. ‘The corundum-bearing serpentines, amphibolites, and _ chlorite- schists are simply derivatives of the foregoing types, with more or less dynamic and chemical alteration and rearrangement. Corundum-bearing gneisses and mica schists, which sometimes pass into quartz-schists, have no relation with the peridotites, although occurring in the same region and sometimes near the outcrops of these rocks. The chief localities of corundiferous peridotites, gneisses, and schists are in Clay, Macon, and Jackson Counties, North Carolina, near the southwestern corner of the state. Scattering occurrences in amphibolites and gneisses are also found east of the mountains, particularly in Iredell County.
The distribution of corundum is considered in chapter viii. First the Appalachian localities are described, including Alabama, Georgia, South Carolina, North Carolina, Virginia, Pennsylvania, New Jersey, New York, Connecticut, and Massachusetts. Occurrences in Montana, Colorado, and California are also described, as well as the corundum and emery deposits of Canada, India, Turkey, and the Grecian islands. North Carolina localities are described in detail, by counties.
The alterations of corundum and the minerals associated with it are described in chapter ix. The list of associated minerals from North Carolina localities includes 62 species, each of which is described, with its mode of occurrence and its relations to the corundum. Chemical analy- ses and crystallographic characters of many are also given. From other American and foreign localities the number of associated minerals is increased to seventy-four.
The origin of corundum is considered in chapter x. The discussion is prefaced by an account of the artificial production of the mineral and a summary of the various hypotheses that have been advanced during the last twenty-five years. From a consideration of field relations and the later experiments with silicate magmas, the conclusion is reached that the corundum of the peridotites was held in solution in the magma when it was injected into the gneisses, and that it crystallized out among the first minerals formed, as the mass began to solidify. Corundum in quart- schists and gneisses, on the other hand, is the result of metamorphism of
‘veins,”’
REVIEWS QI
sandstones and shales rich in alumina, which was probably in the form of bauxite.
Methods of prospecting, mining, and milling are described in chapter xi. It is prefaced by a historical sketch of corundum in the East and an account of discoveries and mining in the United States and Canada.
Chapter xii deals with the various other economic minerals of the peridotite belt—chromite, asbestos, genthite, serpentine, and limonite. Chromite in promising quantities has been found at a number of localities in North Carolina, particularly in Yancey and Jackson Counties. Asbestos (chrysotile) of good quality frequently occurs, but no mining has yet devel- oped in North Carolina. The well-known Canadian deposits, however, are in the northward extension of this belt. The nickel ores (genthite and related silicates) occur widely, and are unquestionably derived from the decomposing peridotites, in the joints of which they are found. Serpen- tine in large bodies is a direct alteration product of the peridotites in North Carolina, but its occurrence is extremely limited, as compared with the abundance of the latter. Residual limonite beds have sometimes been formed from decomposing peridotites, and these have been utilized as iron ores in some portions of the belt in New York and Pennsylvania.
An appendix of twenty pages consists of a bibliography of American peridotites, corundum, and associated minerals. Copious references to both American and foreign literature are also given in footnotes throughout the report.
J. VoLNEY LEWIS RUTGERS COLLEGE
New Brunswick, N. J.
Lower Paleozoic Formations in New Mexico. By C. H. GORDON and L. C. Graton. (American Journal of Science, Vol. XXI, PP- 390-95, 1906.)
In Science for April 13, 1906, announcement was made of the discovery in Sierra and Grant counties, New Mexico, of formations belonging to the Cambrian, Ordovician, Silurian, and Devonian series. A more extended account of these formations by C. H. Gordon and L. C. Graton of the U. S. Geological Survey appeared in the American Journal oj Science for May, 1906. A full account of the investigations upon which these announcements are based will appear in a forthcoming report of the U. S. Geological Survey, on the mining districts of New Mexico.
The Cambrian rocks consist of quartzites, sandstones, and shales, with occasional beds of limestone. They range in thickness from 50
92 REVIEWS
feet, in the Caballos Mountains, to about 1,100 feet in the vicinity of Silver City. ‘To these beds in the forthcoming report the name ‘‘Shandon quartzite” is applied. They contain Upper Cambrian fossils.
Resting with apparent conformity upon the Cambrian is a series of limestones goo to 1,200 feet thick. The greater part of these limestones contain a fauna allied to that of the Richmond division of the Upper Ordovician. In some localities a Silurian fauna appears, but no strati- graphic break between these beds and the Ordovician has been recog- nized, and the indications are that the Silurian beds do not exceed 100 feet in thickness. The data at hand are insufficient to warrant the sepa- ration of these strata, and the name ‘“‘Mimbres” is given to the whole limestone formation.
Resting upon the Mimbres limestones are shales varying in thickness from less than 200 feet in Sierra County to 500 or more in Grant County. The abundant fauna of the lower half of the formation is Upper Devonian. It is of peculiar interest, as it is the same which was discovered years ago in the Ouray limestone in southwestern Colorado by Endlich. It is characterized by Camerotoechia endlichi Meek, not heretofore recognized outside of the San Juan Mountains. For this shale formation the name “Percha”’ has been adopted.
Lower Carboniferous strata have long been known about Lake Val- ley, Sierra County. They have not been found at other localities, notably at Hillsboro, Kingston, Cooks, and in the Silver City district. The name ‘“‘Lake Valley limestones,” formerly applied to these beds, has been adopted by the U. S. Geological Survey.
The Post-Tertiary stratified deposits of gravels and sands have great development in the Rio Grande Valley, where their thickness is some- times 1,500 to 2,000 feet. They occupy old valleys, and the materials are of local origin. The constituents, which are coarse and angular along the borders of the containing depressions, become finer toward the axes of the valleys; and where the valleys are wide, as in the case of the Rio Grande, the axial portions consist principally of sands and inco- herent sandstones. In western Sierra County the coarse gravels are in places cemented into a firm conglomerate comparable to that to which the name Gila Conglomerate is given in Arizona. Extensive exposures of the gravels occur along the Palomas River, and the name ‘‘ Palomas” has been adopted for the formation.
[AuTHORS’ ABSTRACT]
femRNAL OF GEOLOGY
FEBRUARY-MARCH 1907
Ete DEVONIAN SECTION OF ITHACA, N.Y... PART Ti
THE DISCRIMINATION OF THE NUNDA-CHEMUNG BOUNDARY
HENRY SHALER WILLIAMS ithacas Ne Ye
[Concluded from page 598] THE CHEMUNG GROUP OF HALL
The name Chemung group was originally proposed by James Hall in the Third Annual Report of the New York State Geological Sur- vey (p. 324), published as “Assembly Document No. 275” in 1830. The formation was described and lithologically distinguished from the rocks of the immediately underlying formation by the following characteristics:
The tops of the hills and high grounds in the towns of Erie, Veteran, and Catlin, display a group of rocks and fossils very distinct from those last described. The essential difference is the lithological characters of the sandstone of this group in the absence of argillaceous matter in most of the layers, these being merely a pure siliceous rock, harsh to the touch, and generally of a porous texture; while still a large proportion of the mass consists of compact shales and argil- laceous sandstones of a softer texture than those below. The surface of the sand- stones is rough, while those below are smooth and glossy, and being never rippled, prove that the rocks were deposited in a quiet sea. (P. 322.)
This definition gives a fair idea of the most conspicuous differ- ences separating the higher from the lower rocks of these sections,
t Published by permission of the Director of the United States Geological Survey. Concluded from p. 598 of Vol. XIV, No. 7 (1906).
Vol. XV, No. 2 93
94 HENRY SHALER WILLIAMS
though it would be difficult to draw a sharp line at the horizon where the change takes place.
The shales of the Nunda and Chemung are similar, but the sand- stones of the Nunda are smooth surfaced, often ripple marked, thin and tough in texture; while they are soft, rough surfaced, breaking up with vertical rather than splintery fracture (“blocky” as I have called them), in the Chemung and are often of a lighter color.
In Hall’s original definition of the formation certain fossils are mentioned as charactersitic: ‘The principal ones are a species of Delthyris the shell on each side extending into a wing (D. alata?) a Leptaena, Orthis, and a species of Avicula or Pterinea,” etc., but we find a fuller list given in the final report published in 1844. Still more important than this citation of fossils for the purpose of iden- tifying the typical characteristics of the formation is the following statement:
Between Elmira and Chemung they are seen at numerous points, but nowhere in the county [Chemung] so well as at the Chemung upper Narrows, about eleven miles below Elmira. Here the excavation for the road along the margin of the river has exposed more than too feet of rocks, containing abundance of the characteristic fossils, and in their greatest beauty and perfection. (P. 323.)
This quotation indicates where may be found the typical repre- sentation of the fauna and, since in later papers the author [James Hall] lessened his belief in the separateness of the faunas of the Ithaca and Chemung, this standard section is important as it enables us now to scrutinize it more closely than Hall did and to discover the paleontologic marks by which it may be distinguished from the fauna underlying it.
Adopting therefore this section at the upper Chemung Narrows as containing the typical Chemung fauna, as recognized at the time of the original recognition and naming of the Chemung group by James Hall, we may select from the fossils named as characteristic of the Chemung group in the final report (1843) those which are known to belong to the section of rocks exposed at Chemung Nar- rows (Geol. of Fourth Dist., N. Y., pp. 262 ff.).
The species originally mentioned by Hall as coming from the rocks at Chemung and Cayuta Creek? (the latter has been found by
t Ch.=Chemung; Cy.—Cayuta Creek.
DEVONIAN SECTION. OF ITHACA, N.Y. 95
later investigations to represent the same portion of the section as that seen at the cliff at the Narrows above Chemung) are the fol- lowing, viz.:
Calymene nupera (Fig. 116, p. 262, Ch.) =Phacops nupera.
Avicula pectenformis (Fig. 117, 1, 2, p. 262, Ch., Cy.) =Pterinea chemungen- sis (Con.).
Avicula spinigera (Fig. 117, 4, p. 262, Ch.) =Leptodesma spiningerum.
Strophomena bifurcata (Fig. 120-2, Ch.) =Orthothetes chemungensis.
Strophomena arctostriata (Fig. 120, 3, Ch.) =Orthothetes chemungensis.
Strophemena interstrialis (Fig. 120, 5, Ch.) =Dovillina mucronata (Con.).
Orthis carinata (Fig. 121, 1, Ch.) =Dalmanella carinata.
Orthis interlineata (Fig. 121, 3, 4, Ch., Cy.) =Dalmanella tioga (Hall).
Delthyris mesastrialis (Fig. 122, 1, 1a, Cy.) =Spirifer mesistrialis.
Delthyris disjuncta ? H. (Fig. 122, 3, Ch.) =Spirifer disjunctus Sowerby.
Delthyris cuspidata H. (Fig. 123, 1, Ch., Cy.) =Sp. disjunctus Sow.
Delthyris acanthota H. (Fig. 123, 2, 2a, Ch., Cy.) =Sp. disjunctus Sow.
Delthyris acuminata H. (Fig. 123, 5, 5a, Ch., Cy.) =Delthyris mesicostalis.
Atrypa dumosa (Fig. 124, 1, 1a, Ch., Cy.) =Atrypa spinosa (Hall).
Atrypa tribulis (Fig. 124, 3, Ch.) =Atrypa reticularis (Lin).
Cyathophyllum p. (Fig. 273, Ch.) =?
Conrad* in 1842 described several species, the locality of which is sufficiently well certified to refer them to this fauna. The species are (all from Chemung Narrows):
Avicula spinigera (p. 237, Pl. 12, Fig. 3) =Leptodesma spinigerum (Con.).
Avicula protexa (p. 238, Pl. 12, Fig. 6) =Leptodesma protextum (Con.).
Avicula multilineata (p. 241, Pl. 13, Fig. 1) =Avicula multilineata (Con.).
Avicula chemungensis (p. 243) =Pterinea Chemungensis (Con.).
Cypricardites carinifera (p. 245, Pl. 13, Fig. 14) =Goniophora chemungensis.
Inoceramus chemungensis (p. 246, Pl. 13, Fig. 9) =Mytilarca chemungensis (Con.). 2 Nuculites chemungensis (p. 247, Pl. 13, Fig. 13) =Schizodus chemungensis (Con.).
Strophomena lachrymosa (p. 256, Pl. 14, Fig. 9) =Productella lachrymosa (Con.).
Strophomena lima (p. 256) P. lachrymosa var. lima (Con.).
Strophomena mucronata (p. 257, Pl. 14, Fig. 1o)=Douvillina mucronata (Con.).
Strophomena chemungensis (p. 257, Pl. 14, Fig. 12) =Orthothetes chemungen- sis.
t “Observations on the Silurian and Devonian systems of the United States with Descriptions of New Organic Remains,” Jour. Acad. Nat. Sci., VIII (Jan. 18, 1842), pp. 228, etc.
96 HENRY SHALER WILLIAMS
Strophomena delthyris (p. 258, Pl. 14, Fig. 19) =(?) Leptostrophia perplana.
Delthyris chemungensis (p. 263) =Spirifer disjunctus.
Atrypa chemungensis (p. 265)=Atrypa reticularis.
In the Final Reports on Paleontology,’ a large number of species were added to these lists, but for the purpose of determining the typical Chemung fauna and settling its lower boundary these species should furnish conclusive evidence. Those of the list which are restricted in range in this original section may fairly be regarded as
diagnostic of the Chemung formation at its typical outcrop. The two lists contain the following twenty species:
. Phacops nupera (Hall). . Pterinea chemungensis (Hall).
Il. I2.
P. lachrymosa var. lima (Hall). Stropheodonta (Douvillina) muconata (Vanuxem)-
3. Leptodesma spinigerum (Conrad). 13. Leptostrophia (? perplana) 4. L. protextum (Conrad). delthyris (Conrad)- 5. Avicula multilineata (Conrad). 14. Dalmanella carinata (Hall). 6. Goniophora chemungensis 15. Dalmanella tioga (Hall). (Conrad) 16. Spirifer disjunctus (Sowerby).
oOo own
. Mytilarca chemungensis (Conrad). . Schizodus chemungensis (Conrad). . Orthothetes chemungensis (Hall). Io.
Productella lachrymosa (Hall).
. Spirifer mesistrialis (Hall).
. Delthyris mesicostalis (Hall). . Atrypa spinosa (Hall).
. Atrypa reticularis (Linn).
Of these species No. 1, Phacops nu pera, is a variety of the common species P. rana, if not identical; but it was obtained from a loose block, as we are told in Paleontology, Vol. VII, p. 27, so that it is not certainly a part of the original Chemung fauna.
No. 5, Avicula multilineata, is not referred to in later literature, and for correlation purposes it is too rare to serve as a diagnostic species.
No. 8, Schizodus chemungensis, is reported as from “near Ithaca and Cortland,’’? and as the rocks of these localities are now known to lie at a horizon lower than the rocks of Chemung Narrows, the species ceases to be diagnostic of the latter formation.
No. 9, Orthothetes chemungensis, as a species has a considerable range: it is quite variable in its Chemung expression, so that the name without restriction will not constitute it a diagnostic species of the Chemung.
t Paleontology of New York, Vols. IV, V, VI, VII, and VIII.
2 Paleontology of New York, Vol. II, p. 454.
DEVONTPAN, SECLION@“OF TRAACA, IN. Y. 97
No. 13, called Strophomena delthyris by Conrad, is quite distinct from the form described by the same name under the name Siroph- omena perplana to which it has been referred by Hall. If it be a variety of Sir. perplana Conrad, it is sufficiently distinct to receive a distinct varietal name, and then will appear as Leptostrophia per- plana delthyris (Con.).
Hall did not recognize the species called by him Strophomena nervosa? as coming from the Chemung Narrows section; nor does he list it from that section in the final description of the variety.? It may therefore be discarded from a strictly diagnostic list.
No. 17, Spirifer mesistrialis, in the final description of the species is listed from near Cortlandville in Cortland County. The rocks there exposed are stratigraphically at a lower horizon than Chemung, so that the species will not serve to settle the question as to whether the Chemung fauna is or is not identical with that of the Ithaca member.
No. 18, Delthyris mesicostalis Hall. ‘This species was described from a specimen from Angelica, N. Y., and was not reported by Hall from the Chemung Narrows section. ‘The form which has later been identified as of this species, was originally described as Del- thyris acuminata by Hall; this specific name was dropped because it had already been used by Conrad for a Spirifer. This latter form was recognized by Hall as coming from Ithaca, and Cayuta Creek.
This form (referred to by Hall under the name Delthyris acumt- nata) is a common Chemung species; but the discovery of its inti- mate association with the Tropidoleptus fauna, its close affinity with Delthyris consobrinus (also a Hamilton species), and its occurrence in the Van Etten and White Church zones of Tropidoleptus entirely below the range of Spirijer disjunctus, the Dalmanellas, the Dou- villinas, and Plerinea chemungensis, has led me to believe that it does not belong to the typical Chemung fauna, any more than do Tropidoleptus carinatus and Rhipidomella vanuxemi, both of which are abundant in some zones of the section at Chemung Narrows.
Independently, therefore, of the question as to whether there is
t Final Rept. Fourth Dist. (1843), p. 266, Fig. 1.
2 Paleontology, etc., Vol. IV, 113, 114.
3 Report Fourth Dist. N. Y. (1843), p. 271.
98 HENRY SHALER WILLIAMS
a distinction between the Ithaca and Chemung forms going under the name, this species cannot be regarded as strictly diagnostic of the typical Chemung fauna.
Nos. 19 and 20, Alrypa spinosa and Atrypa reticularis, are both recorded from lower horizons than the Chemung by Hall in the Paleontology of New York,* so that they too must be discarded from the list as not strictly diagnostic of the fauna.
DIAGNOSTIC SPECIES OF THE TYPICAL CHEMUNG FAUNA
Excluding the above mentioned species there are left the following eleven species characteristic of the original Chemung group, as expressed in the section at Chemung Narrows a few miles west of the town of Chemung, viz.: Plerinea chemungensis, Leptodesma spinigerum, Leptodesma protextum, Goniophora chemungensis, M yti- larca chemungensis, Productella lachrymosa, P. lachrymosa lima, Stropheodonta (Douvillina) mucronata (Van.), Dalmanella carinata, Dalmanella tioga, Spirijer disjunctus. ‘The question may appro- priately be raised what is the known vertical range of these species, and how sharply may the Nunda-Chemung boundary be drawn by means of their appearance in the rocks ?
Range oj the species.—The first species, Pterinea chemungensis (Conrad), is reported only from this Chemung locality and formation in the Paleontology of New York.? In that volume several closely allied species are described; in the case of none of the species is a locality or range indicated which would exclude them from this fauna. The species are Pterinea consimilis Hall, from Bucks quarry and Chemung, Chemung County, and Smithboro, Tioga County; Pterinea rigida Hall, from several localities in Chemung County; Pterinea prora Hall, from Bucks quarry and Chemung upper Nar- rows; also Pterinea (Vertumnia) reversa Hall, and Pterinea (Ver- tumnia) avis Hall; the subgenus Vertumnia was erected on the character of reversal of the characters of the opposite valves of the shell so that the right valve of Vertumnia appears like the left valve of typical Pterinea The species of Vertumnia are also restricted to the horizons through which the normal species range.
1 Op. cit., Vol. IV, 1867, pp. 321, 325.
2 Op. cit., Vol. V, 1884, p. 98.
DEVONIAN SECTION OF ITHACA, N. Y. 99
In the sections examined in the Watkin’s Glen quadrangle the range of all these species of Pterinea. is restricted to the Cayuta member of the Chemung formation, as defined in this paper, except in a few doubtful cases where the species run higher up than the supposed termination of the Cayuta member into the Wellsburg.
Eastward, in the Harford quadrangle, the species Pterinea che- mungensis has been discovered at a horizon below the range of the other species of the Chemung fauna. The fauna with which it is there associated is however sufficiently distinct from the typical Chemung fauna to leave little doubt as to a lower horizon. In one case Clarke has reported it at the extreme eastern edge of the Harford quadrangle in association with Strophedonta cayuta.' Neither of those species has been discovered in the Watkin’s Glen quadrangle below the base of the Chemung formation. Clarke also records Stropheodonta cayuta in the West Hill sandstone of the Canandaigua and Naples quad- rangles? and in the West Hill flags and shales of the Watkins and Elmira quadrangles.
While a failure to discover fossils is no evidence that they are wanting, it may be stated that none of the surveying party with the present writer examining the rocks of the Watkins Glen quadrangle has discovered either the Pterinea or the Douvillina below the strati- graphic base of the Chemung, thus making both of these species a fairly satisfactory evidence of a Chemung horizon for the Watkins Glen quadrangle, though it is not possible to say that they do not appear at a lower level within this province.
Leptodesma spinigerum and Leptodesma protextum are recorded from Chemung Narrows and both occur in the Chemung section there. They, however, vary so greatly in form and differ so slightly from the typical Leptodesma Rogersi; and there are so many species defined upon slight differences of form, that it will be difficult, with- out a more exhaustive study than has been given them to use species of this genus in defining the limits of the Chemung fauna. From the fact of the frequent abundance of species of this genus in the zones carrying such other species as Tvopidoleptus carinatus and Rhipi- domela vanuxemi, I am inclined to think that they belong to the
tN. Y. State Mus. Bull. 82, 1905, locality number 2499, pp. 53-70.
2N. Y. State-Mus. Bull. 63, 1904, p. 64.
Kore) HENRY SHALER WILLIAMS
incursions of the Hamilton species into the region, rather than to the typical Chemung fauna. The Leptodesmas are not abundant in typical Chemung faunules although they are abundant in zones included in the Chemung formation.
Goniophora chemungensis (Van.).—In Hall’s monograph on the Devonian Lamellibranchiata’ this species is recorded from only the localities ““Chemung Narrows and near Owego and Binghamton,” all of which localities are estimated to be within the same stratigraphic limits, i. e., the Chemung.
In citing the above specific name, it should be noted that the original of the species named Chemung cypricardite (C. chemungensis) by Vanuxem? came from a locality “at the small bridge on the road to Lisle from Binghamton;” and the specimen coming from Che- mung Narrows was described under the name Cypricardites carini- jera by Conrad.$
Also, a closely related form was described by Conrad under the name Cypricardites carinata from “near Oneonta.”4 This latter specimen is figured on Plate II of the Fijieenth Annual Report of the State Museum.’ Its close resemblance to the form figured by Vanuxem is evident. In fact Hall expressed his opinion that the original of Conrad’s species Cypricardites carinaius is identical with Vanuxem’s Cypricardites chemungensis;° but in his final monograph (above referred to), he recognized the two species as distinct. Thusin a critical case of identification, when stratigraphic horizon is in doubt, care should be taken to make clear the actual difference in form between the Hamilton form of the genus and the higher one coming from the Chemung. The horizon of the locality from. which the original of Conrad’s species Goniophora carinata came is in dispute. Its asso- ciation with Paracyclas lirata does not prove it to belong to the Hamilton fauna, as pointed out by Prosser.? While the species
t Paleontology of New York, Vol. V, Pt. I, li (1885), p. 303.
2 Rept. Third Dist. N. Y. (1842), pp. 179, 181.
3 Jour. Acad. Nat. Sci. (1842), Vol. VIII, p. 245.
4 Fijth Ann. Rept. N. Y. Geol. Surv. (1841), p. 53.
5 1862, Pl. II, Fig. 21.
6 Hall and Whitfield, Preliminary Notice of the Lamellibranch Shells, etc..(1869), Pp: 44-
7 Seventeenth Ann. Rept. State Geologist, N. Y. (1900), p. 80.
DEVONIAN SECTION OF ITHACA, N. Y. IOl
described by Conrad as Cypricardites carinijera and that named and figured by Vanuxem as Cypricardites chemungensis undoubtedly occur at Chemung Narrows in the typical Chemung fauna, the char- acters by which they may be discriminated from other representa- tives of the same genus at horizons below the range of other typical Chemung species are too vaguely established to make certain that the species is confined to the Chemung formation. Closely related species of the genus do certainly occur below and probably above the Chemung formation.
Mytilarca chemungensis.—As a genus Mytilarca ranges through- out the Devonian and upward into the lower formations of the carbon- iferous and both the elongate form M. chemungensis and the shorter form M. carinata are frequently met with in the Chemung rocks. Several other species have been described from rocks of other than the typical section referred to the Chemung formation. The forms from the Ithaca and lower horizons most closely resembling the Chemung species are more gibbous, and upon this character and the more narrow form of the Chemung representatives of the genus they may be distinguished. So that this species and its closely related species may be used as strongly suggesting, if not strictly indicative, of a Chemung horizon.
One of the localities (2517) referred to by J. M. Clarke in the paper before mentioned as containing Pterinea chemungensis is also reported as holding Mytilarca chemungensis. Another significant species is Leptostrophia nervosa. ‘The combination is one suggesting the Chemung fauna but the horizon is not clear. Clarke reports the locality as “‘ Ithaca beds.” *
Productella lachrymosa (Con.) and P. lachrymosa var. lima (Con.). —There is no doubt that forms of the genus Productella falling strictly under the description of Conrad’s species Strophomena lachry- mosa are present in the typical Chemung zone at Chemung Narrows as well as the variety S. lima. ‘The question may be raised, however, whether this species is diagnostic of the Chemung fauna in New York state. Examination of a large number of faunules containing representatives of the genus demonstrate that the prominent char- acteristics of P. lachrymosa, 1. e., the ventricose general form, large
tN. Y. State Mus. Bull., 82, p. 60.
102 HENRY SHALER WILLIAMS
size for the genus and elongate tubercles scattered sparsely over the surface, become conspicuous at the horizon where the line between Nunda and Chemung is drawn. Nevertheless, specimens occur below this line which might be referred to the species, though they do not express the dominant characteristics of the species at these lower horizons. The dominant forms in the faunules below the line differ either in size, and thus become referable to the species P. shumardiana or P. spinulicosta; or else differ in the surface markings and fall under the definition of P. speciosa in which also the form is less ventri- cose and the initial umbonal portion is relatively sharper and nar- rower in relation to the full dimensions of the shell. The Chemung fauna is therefore characterized by the presence of Productella lach- rymosa and its variety P. lima, but on account of the great plasticity of the genus, and the fact that the genus is abundantly represented in the Brachiopod faunules anywhere above the Genesee as at present defined, it cannot be said that the species as defined is strictly diag- nostic of a Chemung fauna and horizon.
Stropheodonta (Douvillina) mucronata (Con.).—This species was originally described by Conrad under the name Strophomena mucro- naia, from Chemung Narrows, associated with Productella lachry- mosa.* It was next referred to by Hall under the name Siro phomena interstrialis. Hall regarded it at that time as identical with Phillips’ species of that name.’ Later Hall described the same species as a new species under the name Stropheodonta cayuta,3 applying the name proposed by Conrad to the form occurring abundantly at Ithaca which had been already well figured by Vanuxem4 under the name Sirophomena interstrialis. Wall thus confused under the specific name mucronata, both species which he distinguished in the separa- tion of the original figures in his report as 5 and sa from 50 and 50, referring the latter two, which present the typical character of Con- rad’s description to a new specific name Stropheodonta cayuta, and applying Conrad’s name to the first two of the set which do not offer the distinctive characteristics of Conrad’s description. The result,
t Conrad, Jour. Acad. Nat. Sci. (1842), p. 257, Pl. 14, Fig. 10. 2 Hall, Geol. Fourth Dist. N. Y. (1843), p. 266, Fig. 5.
3 Hall, Paleography of New York, Vol. V (1867), p. 110.
+ Vanuxemi, Geol. N. Y. Rept. Fourth Dist. (1842), p. 174.
DEVONIAN SECTION OF ITHACA, N. Y. 103
which has come to light in noting the subgeneric differences indicated by the names Leptostrophia H. and C. and Douvillina Oehlert, is that the species characteristic of the Chemung fauna of New York, is the one originally described by Conrad from Chemung Narrows. This species belongs to the subgenus Douvillina and is properly there- fore named Stropheodonta (Douvillina) mucronata (Con.). |
All the faunules collected by the writer’s party in the Watkin’s Glen and Catatonk quadrangles which contain this species offer no evidence to contradict their reference to the Chemung fauna and Chemung formations as defined in this paper. No case has been discovered by them of the presence of the species at a horizon below the Chemung base. In the two quadrangles 183 faunules have been examined containing this species and of none of them is there any reasonable doubt (either structural or paleontological) as to their stratigraphic position above the Nunda-Chemung boundary as estab- lished in this classification.
A faunule from Marathon reservior, R. Ruedemann collector, No. 2499, is reported by J. M. Clarke as belonging to the “Ithaca beds.”* Although the altitude is not given several of the species named do not indicate a horizon so low as the Ithaca. ‘The species listed are:
Tentaculites sp. incert; Actinopteria eta. (Hall); Pterinea chemungensis (Con.); Grammysia bisulcata (Con.); Microdon bellistriatus (Con.); Nucula varicosa (Hall ?); Palaeoneilo emarginata (Con.); P. tenuistriata (Hall); P. sp. incert; Schizophoria impressa (Hall); Leptostrophia mucronata (Con.); Stropheodonta cayuta (Hall); Sir. cf demissa (Con.); Chonetes scitula (Hall); Productella lachrymosa (Con.); P. sp. incert.; Spirifer mucronatus (Con.); S. mzcronatus posterus (H. and C.); S. mesastrialis (Hall); S. laevis (Hall); Atrypa reticularis; Cyrtina hamiltonensis var. recta (Hall); Pugnax pugnus var. altus Calv.; Leior- hynchus globuliformis (Van); Strictopora gilberti; Hederella; Plumalina pluma- rea (Hall); Taxocrinus; Auloprora; Boring sponge; Lepidodendron; Dadoxylon.
The species whose place in this list seem to the writer questionable are Pterinea chemungensis, Stropheodonta cayuta, and Productella lachrymosa. If these species are correctly identified and occur in association with the other species listed they are not in accord with the evidence gathered by our party at Marathon, and in fact through- out the whole of the Catatonk quadrangle.
tN. Y. State Mus. Bull. 82, pp. 59 ff.
104 HENRY SHALER WILLIAMS
Dalmanella carinata Hall is described as coming from the localities Painted-Post, Chemung, and Jasper’ under the name Orthis carinata. But in the final