GLACIAL AND POST-GLACIAL HISTORY 659 



RELATION OF HIGHER GLACIAL LAKE CHAMPLAIN TO IROQUOIS. 



Lake Iroquois was made by the ice blocking the St. Lawrence 

 and causing the waters in the Ontario basin to overflow at the lowest 

 point of the basin which was then near Rome, N. Y. During the 

 retreat of the ice a differential uplift was in progress greater at the 

 north. G. K. Gilbert says that when the Rome outlet (present level, 

 440 feet above tide) was abandoned at the close of the Iroquois epoch, 

 "the water of the Ontario basin descended for a time along a course 

 beginning near Covey Hill, and ending near West Chazy, N. Y." ^ 

 Whether these levels are marked by shore terraces is not stated. If 

 they are, it would seem that when the ice retired far enough north 

 in the Champlain Valley, the waters of the Ontario and Champlain 

 basins coalesced. This water body might properly be called Lake 

 St. Lawrence — a name suggested by Upham in 1895.^ ^^ these levels 

 are not marked by shore terraces, but simply by a series of outlet 

 levels,^ then it would seem that the waters of Higher Glacial Lake 

 Champlain and the successor to Lake Iroquois did not coalesce, at 

 any rate not until the close of Higher Glacial Lake Champlain time, 

 when both fell to the levels which have been called "Marine" Cham- 

 plain levels although the highest of these levels do not seem to contain 

 marine fossils (see p. 626). 



During "Marine" Champlain time these waters not only occupied 

 the Champlain Valley, but extended into the Ontario basin, as is 

 shown by the fact that the "marine" shores of the Champlain Valley 

 extend westward through northern New York to the Ontario basin, 

 being continuous with the so-called Oswego shore line.^ In the Ontario 

 basin as in the Champlain basin there is evidence of differential 

 uplift greater at the north, in the late stages of the ice-retreat. 



DURATION OF HUDSON WATER BODY. 



If the Brooklyn- Perth Amboy moraine be correlated with the 

 earliest Late Wisconsin terminal moraine, the history of the Hudson 



1 Eighteenth Annual Report, U. S. Geological Survey, Vol. I, p- 59- 



2 See American Journal 0} Science, Vol. CXLIX (1895), pp. 1-18; Monograph 

 XXV, U. S. Geological Survey, p. 264. See also this article, p. 626. 



3 Since this was written and placed in the hands of the printer the writer has 

 learned from conversation with Mr. Gilbert that this is the fact. 



4 G. K. Gilbert, loc. cit. 



