Geology . Fig. 517.—A later stage in the development of Lakes Chicago and Maumee. The icehas retreated farther, and the outlet of Lake Maumee has been shifted. (Leverettand Taylor, U. S. Geol. Surv.) the thumb of eastern Michigan was discovered, and the Imlayoutlet was abandoned. Later, the whole Erie basin, and a portion of that of Ontario, becamefree from ice, and a lake twice the area of the present Lake Erie developed(Lake Arkona), and was marked by its own set of beaches. Accordingto the recent determinations of Taylor, an advance of the ice followed,closing the lower outlet across the Th
Geology . Fig. 517.—A later stage in the development of Lakes Chicago and Maumee. The icehas retreated farther, and the outlet of Lake Maumee has been shifted. (Leverettand Taylor, U. S. Geol. Surv.) the thumb of eastern Michigan was discovered, and the Imlayoutlet was abandoned. Later, the whole Erie basin, and a portion of that of Ontario, becamefree from ice, and a lake twice the area of the present Lake Erie developed(Lake Arkona), and was marked by its own set of beaches. Accordingto the recent determinations of Taylor, an advance of the ice followed,closing the lower outlet across the Thumb of Michigan, and forcingthe water to occupy a higher one at L^bly. This stage was attendedby the formation of a beach (the Belmore) at a higher level than theArkona beaches, which were submerged but not wholly obliterated. 398 i. 00 J—I 6 fa THE PLEISTOCENE OR GLACIAL PERIOD. 399 The water-body at this stage is known as Lake Whittlesey (). At a still later stage, the Saginaw ice-lobe had retired into theHuron basin, and the ponded waters in the Saginaw basin becameconfluent with those in the Erie basin, which had, in the meantime,become extended into the borders of the Ontario basin, but were blockedin that direction by the Ontario ice-lobe. The extensive water bodythus developed is known as Lake Warren (Fig. 519). At first, thislake discharged through the Grand River outlet into Lake Chicago; butlater the eastern end appears to have worked its way along the southborder of the Ontario ice-lobe into the Finger Lake region of NewYork, and to have reached at length the Mohawk valley, throughwhich it discharged into the Hudson, thus transferring the sea-con-nection of the Erie basin from the Mexican Gulf to the Atlantic the course of time, the shape of the water body centering aboutthe Ontario
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