Ma)i ill tlu: Ice Age. — Uphain. 143 
extension of this glaciation in Iowa, on the west side of the 
Wisconsin driftless area, the ice-lobe east of that area advanced 
from Illinois into the edge of southeastern Iowa, giving an II- 
linoian stage of glaciation which somewhat antedated the maxi- 
mum of the lowan, though not probabl}' by a wide difference 
of time. Between the retreat of the lUinoian ice-lobe and the 
deposition of the lowan loess, Leverett notes interglacial depos- 
its and a zone of weathering, the records of his Sangamon 
stage. lowan time seems correlative with the Polandian stage 
of renewed growth of the European ice-sheet. 
In this late part of the Glacial period the northern lands, 
which had long stood at greater altitudes than now, sank at last 
under their heavy ice-load until they mostly were somewhat be- 
low their present hights. This Champlain depression, as it is 
called, permitted the glacial drift of coastal regions to be cov- 
ered by fossiliferous marine beds, which through later re-ele- 
vation range up to 300 feet above the sea in Maine, 560 feet at 
Montreal, 300 to 400 feet from south to north in the basin of 
lake Champlain, 300 to 500 feet southwest of Hudson and James 
bays, and similar or greater altitudes on the coasts of British 
Columbia, the British Isles, Germany, and Scandinavia. 
Glacial melting and recession from the lowan boundaries 
was rapid under the temperate (and in summers warm or hot) 
climate belonging to the more southern parts of the drift-bear- 
ing areas wdien reduced from their great preglacial elevation 
to their present bight or lower. The liner portion of the drift, 
swept down from the icefields by the abundant waters of their 
melting and of rains, was spread on the lower lands and along 
valley's in front of the departing ice, as the loess of the Missou- 
ri, the Mississippi, and the Rhine. In or just beneath the basal 
beds of the Missouri loess was the Lansing fossil man, belong- 
ing thus to the culmination or beginning of decline of the lo- 
wan stage of glaciation. 
To this time the Columbian formation seems referable, 
succeeding the Lafayette and its erosion in our Atlantic coast 
region. In a Columbian gravel deposit, at Claymont, Del., 
probably of a little later date than the base of the loess at Lan- 
sing, Mr. Hilborne T. Cresson in 1887 found an argilHte im- 
plement, as described and figurecl by I'rof. G. F. Wright in his 
works cited on a following page. 
