| Summary: | 16 GEOLOGY OF THE HILL COUNTRY Kansan—In this Glacial period the ice-sheet attained its greatest extension, and advanced farther south than any other. At the East it reached southward to Long Island, New York Harbor and the northeast and northwest portions of Pennsylvania; in the middle west to Cincinnati, southern Indiana and St. Louis and the eastern parts of Kansas and Nebraska. Farther to the west, the ice margin appears to have been conterminous with the valley of the Missouri river, which above the mouth of James river, was excavated by both land and glacial drainage along the edge of the ice-sheet. There are remains of an old driftsheet west of the Missouri—the Albertan. The iuterglacial stage that followed the melting away of theKansan ice-sheet is accounted as having been more prolonged then any that succeeded it. No geologist would reckon it to have been shorter than 10,000 years. Iilinoian—The ice-sheet of this glacial .epoch did not advance as far southward as the other, unless to the eastward of central Ohio. It is called the Iilinoian stage because its drift- sheet was first identified in Illinois and found to be differentiated from the one below and above it by old soil horizons, of course not present everywhere. Usually the glaciers and accompanying diluvial waters swept away almost all traces of the interglacial forests and soils that formed upon each drift- sheet. Still, much remained. The "buried forests" and vegetal soil horizons and black muck beds, often encountered in digging wells in Ohio and Indiana, with bowlder clay above and below them, were never satisfactorily accounted for by those who maintained iceberg theories or the view that there had been but one Ice age only. Iowan—Recognized in eastern Iowa, and adjoining parts of Minnesota and Illinois, with some fringes of it on the margin of the Driftless Area in southern Wisconsin, emerging from under the well-marked driftsheet of the Wisconsin stage. At the close of the Iowan stage the central part of the continent appears to have subsided to a lower elevation above sea level' Scanned with a Zeutschel Zeta book scanner at 300 dpi. Edited in Multi-page TIFF Editor.
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