| Summary: | 20 GEOLOGY OF THE HILL COUNTRY northern Minnesota and the eastern half of North Dakota, projected south somewhat in the form of two ice lobes. This; ice-sheet had never extended any farther west than the Missouri Coteau or the high hilly land between Mouse river and the Missouri. The junction of the two ice lobes was along the western side of the Red River Valley where the Elk Valley is now. While Lake Agassiz was forming south of the receding ice-sheet, a wide rift opened between the two lobes, making an estuary to a glacial river which came down the narrower part pf the rift extending up toward the Canadian boundary. The glacial river brought down an enormous amount of sediment which settled in the estuary and mainly formed the Elk Val» ley, parallel with the foot of the uplands. The coulees of the hill country were mainly formed by the waters that attended the melting away of the ice-sheet. The drainage lines cut into and sometimes through the driftsheet, lowering the contained pebbles and bowlders to the bottoms of the coulees. The sand and clay was carried into Lake Agassiz. If the bottoms of coulees are smooth and grassy, it is because the stony debris that paves their beds has been sed- imented over. A washed out place shows the stones plainly. It is well known that the gravel, pebbles and bowlders of the hill country is foreign material, brought from the country west of Hudson Kay and around Lake Winnipeg during an Ice age. Most of them are of igneous varieties of rocks, but som» are of limestone. More rarely a sandstone bowlder may be found in the bowlder clay. The bowlders generally are the debris of disintegrated mountains of seamed rocks, finally torn to pieces by ice-sheets. Their rounding was probably not all the result of abrasion during glacial transportation in the bases of ice-sheets. Many of the bowlders doubtless were partially rounded by long preglacial and interglacial weathering. Nor is it likely that all of them in any hill township made their entire journey from the north during a single ice epoch. Scanned with a Zeutschel Zeta book scanner at 300 dpi. Edited in Multi-page TIFF Editor.
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