322 LIFE OF THE PLEISTOCENE 



by Frank Leverett to be several hundred feet thick and of older date than 

 the surface morainal deposits of the region and to rest upon older glacial de- 

 posits. It is thus shown to have been deposited previous to the southward ad- 

 vance of the Wisconsin ice sheet. This is a highly instructive discovery, and if 

 as now seems probable, the pink clays of northern Michigan were deposited in 

 the same lake as the similar clays in southern Michigan, the existence of an 

 inter-glacial lake in the Great Lakes basin of comparable size with Lake Algon- 

 quin is made manifest. " These clays may be of Sangamon age. 



Sherzer 169 mentions Illinoian drift in Monroe County with "coal" (probably 

 compacted peat) above drift; and Davis 170 mentions pre-Wisconsin drift in 

 Tuscola County. Many years ago 171 Wm. Logan recorded the presence of a 

 deposit 12-14 feet thick, containing roots and limbs of trees, at Grand Sable, 

 south shore Lake Superior. The deposit rested on bluish-drab clay and was 

 overlaid by a bed of sand interstratified with gravel 300 feet in thickness. It 

 is not known what interval the vegetation may represent. 



Taylor 1713 states that pre-Wisconsin till occurs beneath the Wisconsin 

 drift in the area of the "Thumb" in Michigan. Of this deposit Taylor says: 

 "Till older than that deposited by the Wisconsin ice sheet seems to underlie 

 more or less continuously all of the later or Wisconsin drift in Indiana and the 

 southern peninsula of Michigan. " Old soil in places overlies this older drift. 



8. NEW YORK 



Evidence is accumulating, indicating the presence of a till sheet beneath 

 the Wisconsin drift sheet. Just which drift sheet is represented has not been 

 definitely stated, but it is apparently referable to the till beneath the interglacial 

 deposits at Toronto, which is thot to be the Illinoian stage. In the Keuka Valley, 

 wave cut terraces have been observed which are believed to have been produced 

 by a pre-Wisconsin glacial lake. 172 In the Finger Lake region of New York a 

 pre-Wisconsin drift has also been detected. 173 In the Mohawk Valley 174 the 

 hardpan referred to in the well sections evidently represents the Illinoian till 

 sheet. 



Well borings in western New York indicate that several drift sheets have 

 crossed the state. Spencer 175 has published a well section taken in the Whirl- 

 pool-Saint Davids gorge, Niagara River, which exhibits several tills and inter- 

 glacial deposits. 



189 Geol. Surv. Mich., VII, part 1, pp. 126-127. 



170 An. Rep. Geol. Surv. Mich., 1908, pp. 121-358. 



171 Geol. of Canada, 1863, p. 905. 



17ia Mon. LIII, U. S. G. S., pp. 261, 289. 



172 Carney, Amer. Journ. Sci., (iv), XXIII, pp. 325-335, 1907. 



173 Carney, Denison Univ. Bull., XIV, pp. 3-18, 35-46, 1908. 



171 Brigham, Bull. Geol. Soc. Amer., IX, pp. 189-190. See also Fairchild, Bull. Geol. 

 Soc. Amer., XX, p. 632. 



176 Bull. Geol. Soc. Amer., XXI, p. 436, 1910. 



