384 PLEISTOCENE OF INDIANA AND MICHIGAN. 



exception to the inset deltas of Lake Whittlesey. This delta is not large, but its relation to 

 the Arkona beaches establishes the time at which it was built. 



In Ontario there are three Whittlesey deltas, each larger than any on the American side. 

 One appears on Grand River between Paris and Brantford, another on Thames River between 

 Komoka and London, and another on a large glacial river which came from the northeast along 

 the ice front and entered the Au Sable Bay of Lake Whittlesey a few miles northwest of Clinton. 

 The first two are inset deltas like those in Michigan. The third, like the one near Alden, N. Y., 

 was built by a river flowing along the ice border. Another smaller delta, formed, like the last, 

 by a river flowing along the ice border, occurs near Guelph Junction, Ontario. The fourth and 

 only other place where such a delta could occur is occupied by the Ubly outlet in Michigan. 



GLACIAL BARRIERS. 



The positions of the ice barriers which retained Lake Whittlesey are more precisely and 

 more completely known than for any other of the larger glacial lakes. The position of the ice 

 front has been traced continuously, with the exception of one short interval, from the east side 

 of Lake Michigan near Muskegon to the Genesee Valley in western New York. The interval 

 remaining untraced lies along the Niagara escarpment south of Collingwood, Ontario. This 

 untraced interval, however, does not affect the identity of the barrier in New York, because the 

 moraine, which is clearly correlated with the Arkona and Whittlesey beaches near Alden, N. Y., 

 has been traced westward through the Niagara Peninsula in Canada and around the west end 

 of Lake Ontario, so that this part has been independently identified as belonging to the same 

 line. On the Lake Michigan slope the Port Huron morainic system appears to be represented 

 by three rather widely deployed ridges which reach the lake shore at Muskegon, Pentwater, 

 and Manistee. The Muskegon ridge appears to be the correlative of the front part of the 

 Port Huron system on the "thumb," and the correlative on the west side of Lake Michigan 

 seems clearly to be a moraine which comes down to the lake shore at Milwaukee, Wis. The 

 position of the western barrier of Lake Whittlesey is shown on figure 6 (p. 370) and a part of 

 it on the east side of the " thumb" is shown in more detail on figure 5 (p. 366). 



Since the early days of glacial studies in the Great Lakes region it has naturally been 

 regarded as a desideratum of the first order to trace a single position of the ice front through 

 the longest possible distance, and if possible to determine its position entirely across the Great 

 Lakes region at one or more of its pauses. Except for the basin of Lake Superior, this result 

 has been accomplished only in the determination of the ice barriers of Lake Whittlesey and the 

 continuation of the same ice front, without a break, to the barriers of Lakes Saginaw and Chicago. 

 Some of the earlier positions of the ice front have been almost as fully made out, but none later 

 than Lake Whittlesey have been traced for anything like such a distance continuously. 



Some years ago the writer 1 conjecturally showed the eastern ice barrier of Lake Whittlesey 

 as running from Alden a little north of west along the south side of Grand Island to the west 

 bank at Niagara Falls, and thence along the edge of the escarpment to Hamilton, Ontario. Later 

 studies, 2 however, have proved that the line of the barrier passes west-southwest from Alden 

 in a broad curve past Elma, Ebenezer, and West Seneca, and thence westward across the north- 

 east end of Lake Erie to the Canadian shore at Crystal Bay. Thence it runs in very faint form 

 parallel with the shore about 2 miles inland to a point north of Low Banks, and thence north- 

 west to a point near Copetown, where it turns around the west end of the Lake Ontario basin 

 and runs northward to Limehouse. Here it drops below the escarpment. 



The moraines which mark the barriers of Lakes Whittlesey and Saginaw were water-laid 

 and in their mid-valley parts, where the water was deepest, are extremely faint. The one at 

 the east is faintest, being scarcely traceable for a part of the distance, except by its control of 

 the minor drainage. The line of the barrier of Lake Chicago is now deeply submerged. 



In character the two moraines which mark the eastern and western barriers of Lake Whit- 

 tlesey are distinctly different. The Port Huron moramic system is of the major class, whereas 



'Mon. U. S. Geo]. Survey, vol. 41, 1902, PI. XXIII. 



^Niagara folio (No. 190) ,Geol. Atlas U. S., U. S. Geol. Survey, 1913, diagrams, pp. 17-18; also Trans. Canadian Inst., vol. 10, 1913, map. 



