BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA

V o l . 25, p p . 205-214 J u n e 18, 19 14

AGE OP THE DON RIVER GLACIAL DEPOSITS, , 1

BY G. FREDERICK WRIGHT

(.Presented by title before the Society January 1, 191k)

CONTENTS Page Introduction...... 205 Statement of facts as to date and duration of Lake W arren...... 205 Age of Lake ...... 207 Origin of the warm species of plants and animals in the Don beds...... 210 The Labrador later than the Keewatin glacier...... 212 Summary...... 213

I ntroduction After a preliminary statement of the main facts, the discussion in this paper will relate (1) to the age of the latest glacial deposits at Toronto connected with the existence of the , and (2) to the earliest interglacial deposits containing animals and plants which are characteristic of a warmer climate than that which prevails even now north of .

S tatement op P acts as to Date and D uration op L ake Warren The occurrence of warm species of plants and animals in interglacial deposits in the Don River Valley, near Toronto, Ontario, seems at first sight an absolute demonstration of an immense interval of time between the two invasions of glacial ice which are there clearly indicated. Briefly stated, the facts are that in the valley of the Don River and at Scarboro heights near Toronto there is at the base a deposit of till which, after having been extensively eroded, was covered by sedimentary deposits of glacial origin 150 feet in thickness which had been brought into standing water by the stream to form a delta whose base extended 25 or 30 miles along the shore. The lower strata of this delta deposit are 35 feet below the present level of the lake and probably at about the same relative level

1 Manuscript received by the Secretary of the Society February 17, 1914. XV—B ull. Geod. Soc. Am., You 25, 1913 (205)

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as when laid down. But the water from some unknown cause rose as the accumulation progressed until it was 150 feet higher than now/ when the upper sediments of coarser gravel were deposited; then the water began to fall and a period of erosion succeeded. This proceeded until at Scarboro a Y-shaped channel, one mile wide at the top and 150 feet deep, was worn in the sedimentary deposits, where­ upon the ice advanced again and covered the whole with sheets of boulder- clay and assorted rubble drift to a total depth of 200 feet. Here certainly seems to be an interglacial deposit of unusual extent. Nor is the character of the fossil plants and animals included in the interglacial deposits any less noteworthy. Both the fauna and the flora of the lower, or Don, bedsindicate a much warmer climate than those of Jmguois Beach the upper, or Scar- boro, beds. In the _____ Don beds there are ,eo 1 - - i-2------S.—— rS° found leaves and wood of maple, elm, ash, hickory, basswood, and even of pawpaw and osage orange, which now flourish only in latitudes several de­ grees south of To­ ronto ; also, of the mollusks found in the F i g u r e 1.— Section of Don Valley Brickyard, Toronto (Coleman) Don beds, four of the species are not now found in the Saint Lawrence basin, but only after passing the watershed which separates it from that of the Mississippi. On the other hand, the upper, or Scarboro, sands and clays are wanting in the species indicating a warmer climate, but abound in both a flora and a fauna suggestive of Labrador and of the region north of .2 In the opinion of Professor Coleman, these facts can not be accounted for except on the supposition that the earlier ice-sheet retired from prac­ tically the whole region to the northward before the latter one began its advance, which certainly looks very reasonable at first sight. But there are a number of considerations, too much overlooked, which seem to compel, or at least to permit, a contrary conclusion.

2 Coleman: “Glacial and interglacial beds near Toronto,” Journal of Geology, vol. 9, pp. 285-310. “Lake Iroquois and its predecessors at Toronto,” Bull. Geol. Soc. Am., vol. 10, 165-176. “On the Pleistocene near Toronto,” British Assoc, for Adv. of Sci., Report 1900, pp. 328-334; Guide Book, No. 6, for International Geological Congress, pp. 10-34.

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A ge of L a k e I boquois

Beginning with the age of the upper shelf worn in the deposits at Toronto, approximately about 200 feet above the level of Lake Ontario, it is to be noted as bearing on the subject: 1. That it is younger by several thousand years than of glacial origin about the south end of and than those formed on the shores of Lake Warren on the south side of . No one will question the statement that the final retreat of glacial ice from the United States and proceeded from the southwest, uncovering successively the western areas of the , until finally the ice barriers to the east over central New York and Quebec gave away and

permitted the drainage of the Great Lakes to pursue its present outlet (see map on opposite page). But for a considerable period there was a drainage leading to the Hudson Valley at a higher level along the ice- front through the valley of the Mohawk River in central New York. Whatever age, therefore, we assign to the erosion of the 200-foot shelf at Toronto, the shorelines at the south of Lake Michigan and those of Lake Warren in Ohio must be much older. 2. But we are compelled to set moderate limits to the time which has elapsed since the ice withdrew from the southern end of Lake Michigan. a. The dunes at the south end of Lake Michigan represent accumula­ tions which have been going on ever since the ice withdrew from that region. They are composed of sand, which is borne along by the waves and currents on the west shore of the lake and is finally caught up by

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the winds to form the dunes which attract the attention of all passengers on the railroad going to Chicago from the east. Prom the amount of these accumulations and from the rate at which the sand is now known to be moving past Chicago along the west side of the lake toward the south end of ifc from 10,000 to 15,000 years is more than ample time to account for the accumulation of the entire mass of the dunes. 6. The waves of Lake Michigan are constantly eating into the west shore at a rate which, according to the most moderate computations, would produce the 70-foot shelf extending out to deep water in less time than that already allowed for the accumulation of the dunes.3 3. The latest glacial deposits on the south side of Lake Erie are found in the beaches that mark the shoreline of Lake Warren, the highest of which is approximately 200 feet above Lake Erie in Ohio. These beaches, I think I have proved conclusively, can not be more than 10,000 or 12,000 years old. The evidence exists in the small amount of erosion that has been accomplished by the streams of northern Ohio, which have been flow­ ing into the Lake Erie basin ever since the retreat of the ice from that region. In particular, attention is directed to the small extent to which Plum Creek, in Oberlin, Ohio, has enlarged its trough. This trough is 50 feet above the highest Lake Warren beach, and only five miles distant, is entirely in glacial deposits, with no rock obstruction, yet it is so narrow and shallow that any calculations making it much more than 12,000 years old, and especially those that make it several multiples of 12,000, involve an absurdly low rate of erosion. Moreover, data have been col­ lected from the present eroding efficiency of the stream which give results well within the above figures.4 4. A clue to the length of time during which Lake Warren continued to cover the bordering land on the south side of Lake Erie is furnished by deposits recently uncovered by excavations at Premont, Ohio. The sedi­ mentary plain on which the city of Fremont is built lies below the 100- foot level of the lowest shoreline of Lake Warren. The sedimentary de­ posits consist of the material brought into Lake Erie by Sandusky River, which is spread out as a delta. The depth of these lacustrine beds is at least 25 feet. The thickness of the lamiuas, according to my measure­ ments made in several excavations, is on an average one-seventh of an inch, making 84 to the foot, making a total of 2,100, which would be the number of years required for the accumulation on the supposition that

8 See the paper of Dr. Edmund Andrews In Transactions of the Chicago Academy of Sciences, vol. ii, 1870, pp. 1-23. This and the later facts bearing on the question are fairly and fully discussed by Leverett in Monograph xxxviil of the U. S. Geol. Survey, pp. 453-459. * See Wright’s “Ice Age in North America,” 5th ed., pp. 564-568; also Bull. Geol. Soc. Am., vol. 23, pp. 278-280.

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each lamina represented an annual deposit. Whatever be the date, there­ fore, which we assign to the upper beach of Lake Warren, that of the Iroquois beach around Lake Ontario must be 2,000 years less. This, according to my calculation, would bring the date of the 200-foot shelf at Toronto at about 10,000 years. 5. To account for the high level of the water in Lake Iroquois, which eroded the 200-foot shelf at Toronto, it is sufficient to note that the shell' has almost exactly the same elevation as that of the col from the Ontario basin into the Mohawk Valley at Rome, JSTew York. Lake Ontario is 247 feet above the sea. The col at Rome is 445. Moreover, as Professor Fairchild has abundantly detailed, ice obstructions in the Mohawk Valley raised the level of the drainage lines into the Mohawk Valley for an in­ definite period.6 One of the clearest evidences of this exists a few miles southeast of Syracuse, where a stream comparable in size to that of Ni­ agara, but in fact doubtless much larger, has eroded a rock gorge of such length and proportions that its formation must have occupied many cen­ turies. This stream must have been kept up at this level by the ice bordering it on the north side and filling the valley. 6. All these considerations show that there must be some error in the assumptions which underlie the calculations which assign a date of from 20,000 to 40,000 years to the formation of Lake Iroquois, to the erosion of the 200-foot shelf at Toronto, and we may add to the age of the N i­ agara Gorge. It should be remembered that all these calculations are based on assumptions underlying the interpretation of very complicated phenomena. Among these assumptions the most misleading are those which unduly minimize the rate at which glacial movements and torren­ tial erosion may take place. By way of caution it is sufficient to call attention to two facts: a. Within 25 years the front of the Muir Glacier, in Alaska, has re­ treated seven miles, while the ablation from its surface during that time amounts to fully 700 feet, thus confirming my original estimate that since Vancouver’s visit in 1794 the glacier has retreated more than 30 miles, and that the ablation of the surface during that time amounts to more than 2,000 feet. This certainly is a movement on a scale sufficiently large to be considered in speculating concerning continental glacial ice- sheets.6 &. Dr. Warren Upham in his exploration of the shoreline of obtained evidence which is ample to show that the retreat of the ice-front from the boundary in the Red River of the North so

B See Fairchild: Bull. Geol. Soc. Am., vol. 10, pp. 27-68 ; “Pleistocene geology of west­ ern New York,” 20th Rep. of State Geol., 1900, pp. 13-139. 6 See Wright’s “Ice Age in North America,” 5th ed., chap. 3, with references.

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as to open the drainage into Hudson Bay did not occupy more than 2,000 years, making the average rate of the retreat of the ice-front one-half mile per annum.7 This evidencei consists largely in the small extent of the dunes at the south end of Lake Agassiz as compared with that of those at the south end of Lake Michigan, and of the small extent of the deltas formed on the western shore of Lake Agassiz deposited by such streams as the Saskatchewan and the Assiniboin. So little is known about the cause of the climatic changes which pro­ duce and terminate glacial periods that speculation apart from the facts at hand is of little value.

Origin of t h e warm Species of P lants and A nimals in th e D on B eds The occurrence of warm species of plants and mollusks, referred to, in the Don Eiver Valley takes us back to the earliest stages of the Glacial period, and at first sight seems to prove, as Professor Coleman maintains, that a warm period intervened in that latitude between two successive glacial advances, and implies that the first ice-sheet completely disappeared from North America and was succeeded by a new and independent move­ ment. But when the evidence is closely examined in the light of other well established facts it would appear that such a sweeping inference is by no means necessary. a. It does not appear that the glacial till below the fluviatile beds in the Don Valley contains any roots of the trees and shrubs supposed to have existed in the inter-Glacial warm period, whereas in front of the Muir Glacier in Alaska my photographs distinctly show such stumps and rootlets projecting from the underlying soil into the fluvial beds that had enveloped them and were subsequently covered over by the glacier’s advance.8 b. It is entirely possible that the specimens of warm species of plants and animals in the fluvial deposits overlying the lower till were derived from the underlying deposit of late Tertiary age, having been plowed up by a readvance of the ice after a temporary recession and raised without much disturbance to the higher levels, where they are now found. This supposition, which would seem incredible until all the elements involved had been taken into consideration, is rendered easily credible by what has been learned in recent times concerning the deposits of Moel Tryfaen

7 See Monograph xxv of U. S. Geol. Survey; Bulletin No. 29, TJ. S. Geol. Survey ; An­ nual Report, Canadian Geol. Survey, n. s., vol. iv, for 1889, part E. The facts are suc­ cinctly stated by Dr. Upham in Wright’s “Ice Age in North America,” 5th ed„ pp. 400- 406 and 543-548. 8 See Wright’s “Ice Age in North America,” 5th ed., p. 63.

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in Wales, Macclesfield in England, and various other places. In these localities well preserved shells, such as occur in the Irish Sea, were pushed up by the glacial movement from the north to an elevation of more than 1,000 feet, where on the melting of the ice they were redeposited in tem­ porary lacustrian pools and preserved in strata of sand marked by every characteristic of cross-bedding.9 While most of these specimens are fragmentary they were by no means all of them so. Professor Kendall reports finding five whole shells in the course of a few hours’ search at Moel Tryfaen alone, while Prof. McKenny Hughes reports that some of the specimens are whole, and he personally assured me that he had found in these deposits some shells with both sides held together by the original ligaments. How these shells could have been brought up to these positions without showing signs of abrasion may be explained on the supposition that large compact masses of the sea-bottom were broken up and pushed before the advancing ice, as great masses of chalk have been pushed inland over the east shore of England and over the southern end of Sweden. Professor Holst took me to visit such a mass of chalk a few miles east of Malmo, which was 3 miles long, 1,000 feet wide, and 100 to 200 feet thick, which had glacial deposits both under it and over it. In the case of a frozen or compact mass of soil containing fossils the process of melting would result in waterlaid deposits containing fossils showing even less signs of abrasion than if carried along tumultuously by a running stream for any considerable distance. All the older geologists interpreted these lacustrian shell beds at Moel Tryfaen and Macclesfield as evidence that the shell-fish had lived and died in that immediate locality, and supposed that to account for them there must have been a subsidence of the British Isles to the extent of more than 1,000 feet, permitting the shells to grow on the ocean bed at the level where they are now found. Among the authorities maintaining this view are to be numbered Darwin, Prestwich, Eamsay, and McKenney Hughes; but at the present time the geologists of Great Britain almost universally regard the deposits as having been formed in the manner de­ scribed. In the case of the deposits under consideration at Toronto, where there has been scarcely any, if any, elevation of the fossils above their original position to get them where they are now found, it would

9 The fullest statement of the evidence bearing on this subject will be found In a com­ munication of Prof. Percy F. Kendall, F. G. S., incorporated in Wright’s “Man and the Glacial Period,” pp. 137-181 ; but see also a paper of T. McKenny Hughes, of Cambridge, England, on “The evidences of the later movements of elevation and depression in the British Isles,” Victoria Inst., 1880. See especially, however, “Supposed interglacial shell-beds in Shropshire,” England, by G. Frederick Wright, in Bull. Geol. Soc. Am., vol. 3, pp. 505-508; and, by the same, “Theory of interglacial submergence in England,” in American Journal of Science, vol. xliii, January, 1892, pp. 1-8.

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seem unwarranted to draw any sweeping conclusion from their occurrence in the lower part of the iluviatile beds overlying the lowest till.

F i g u r e 3 .— Map of North American Pleistocene Ice-sheet at its maximum Extension Showing the approximate southern limit of glaciation, the three main centers of ice accumulation, and the driftless area within the glaciated region. (United States Geo­ logical Survey.)

T h e L abrador later t h a n t h e K e ew a tin G-lacier

In discussing inter-Glacial epochs and their time ratios it would seem that too little attention has been paid to the evidence that in America the glacial movement from the Keewatin center preceded that from Labrador. How far east the early movement of the Keewatin ice-sheet extended it is impossible with our present knowledge to tell with cer­ tainty; but Lake Superior copper has been found in the glacial deposits in Columbus, Ohio, and still farther north and east in Medina County,

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Ohio, and, according to Prof. E. H. Williams, at Warren, in western Pennsylvania, while red jasper conglomerate boulders from north of occur as far east as Ashtabula County, in the extreme north­ eastern part of Ohio. It is hardly possible that these materials could have been transported so far east during the later portions of the glacial invasions, for that invasion consisted of Labradorian ice. The so-called Illinoisan deposits pushed from the eastward across the State of Illinois, and even extended a short distance into eastern Iowa, where in the vicinity of Keokuk red jasper conglomerate boulders from the north of Lake Huron are found in considerable abundance. It is thus certain that the glacial movement from the Labrador center was later than that from the Keewatin center. For a long distance east of the Mississippi River we know that the deposits of the Labrador ice-sheet overlie those of the Keewatin sheet. It is noticeable also, as already indicated, that the ice departed from the western regions long before it disappeared from New York, New England, and Quebec. The distinct signs of inter-Glacial epochs are only in this western field. No satisfactory evidence of ex­ tended inter-Glacial epochs has been found in the eastern regions. As bearing* on the larger question of an inter-Glacial epoch covering the whole northern hemisphere, it is also significant that the geologists of Great Britain now maintain that they discover no evidence of such an inter-Glacial epoch in the British Isles, nor do the geologists of Sweden in Scandinavia.10 I long ago called attention to the fact brought out during the survey of the terminal moraine in Pennsylvania by Professor Lewis and myself that the boundary of the glaciated areas in the central and the eastern part of the United States consists of the arcs of two circles, with their centers respectively in Labrador and the Lake Superior region. The junction of these arcs is at Salamanca, New York, almost exactly on the meridian of Toronto. It is, therefore, a plausible hypothesis that the deposits of Toronto, where these contending ice-fields met, should reveal many abnormal phenomena.

Summary The following order of events would seem to explain all the facts: 1. First, the Keewatin Glacier pushed southward to the glacial limit in the Mississippi Yalley and eastward as far as western Pennsylvania

10 See Lamplugh’s “Presidential address to the geological section of the British Asso­ ciation for the Advancement of Science,” at York, 1906; also paper before the Interna­ tional Geological Congress, at Toronto, 1913 ; also Nils Olof Holst’s “FSrhistorisk gruf- bryting i Sverige,” in which he estimates the close of the Glacial period in Sweden as not more than 7,000 years ago.

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and the center of Lake Ontario, extending in the vicinity of Toronto into a region which was occupied by some species of plants and animals which now exist only at a considerable distance to the south. At that time the lower Don beds were deposited. 2. Later the Labrador Glacier pushed outward as the Keewatin Glacier receded, moving, as is shown by the glacial scratches and transportation of boulders nearly east and west in the basins of lakes Ontario and Erie, and pushing on as far as the Mississippi Eiver at Keokuk, Iowa, there indeed crossing the river for a short distance. During this advance over the deserted Keewatin deposits in the vicinity of Toronto the Scarboro beds, overlying the Don beds, were deposited and some of the fossil plants and animals native to the lower beds incorporated into the lower portions of the upper beds. In the early part of this movement the Eo'me outlet to the Ontario basin was still free from ice and probably at a lower level than now. This was subsequently either filled with ice or gradually ele­ vated so as to account for the rise of the water and the accumulation of the Scarboro beds. 3. On the retreat of the Labrador ice the basin of the upper lakes was uncovered, bringing Lake Warren into existence, while the western boundary of the ice obstructed the drainage to the east. At a later stage this boundary retreated farther east and north, so as to uncover the Eome outlet into the Mohawk Valley, giving rise to Lake Iroquois and allowing for the erosion of the shelf 200 feet above Lake Ontario, now covered by Iroquois sands north of Toronto and Scarboro. The elevation of this Iroquois beach at Toronto corresponds closely to that of the col at Eome. 4. At a later stage the ice retreated so as to open the outlet into the Saint Lawrence. 5. Following this there was the rapid differential rise of land toward the northeast, which elevated the Iroquois beaches toward the north and northeast. Thus we have brought into order all the complicated facts involved in this most puzzling problem, including those which demonstrate the late date of the shorelines of Lake Warren south of Lake Erie in Ohio. Any supposed sequence of events which fails to account for the late date of these shorelines must involve some error which vitiates the theory. While we have no data from which to draw even approximate conclusions con­ cerning the date of the beginning of the Glacial period, there is nothing which would appear to contradict the opinion of the geologists both of England and Sweden that while the departure of the glacial ice-sheets was very rapid, taking place only a few thousand years ago, the advance was very gradual, occupying an immense period and accompanied by numerous temporary intermissions.

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