. Glacial formations and drainage features of the Erie and Ohio basins. dto the glacial drift. In this old channel the silt filling is bu+ little less thanin Teays Valley, the surface of the silt being 680 to 700 feet above tide, or50 to 70 feet above the rock floor. The gravel which underlies the silt is athin deposit resting upon the rock floor. The accompanying map (PLVII),which embraces a portion of the Ironton quadrangle, shows a part of thisold valley and the present Ohio, with a range of hills between them. Thehills occupy the interval between the mouths of White Oak Creek and PondRun.
. Glacial formations and drainage features of the Erie and Ohio basins. dto the glacial drift. In this old channel the silt filling is bu+ little less thanin Teays Valley, the surface of the silt being 680 to 700 feet above tide, or50 to 70 feet above the rock floor. The gravel which underlies the silt is athin deposit resting upon the rock floor. The accompanying map (PLVII),which embraces a portion of the Ironton quadrangle, shows a part of thisold valley and the present Ohio, with a range of hills between them. Thehills occupy the interval between the mouths of White Oak Creek and PondRun. Although they rise in places to a height of more than ] 00 feet abovethe silt filling in the old valley, they are interrupted by notches so low thatsmall streams drain from the old valley through them to the present is probable that the Ohio took advantage of similar low gaps in changingfrom the old course to the present one. Sidney Lyon: Second Geol. Rept. of Kentucky, 1856 and 1857, p. 360.^^E. B. Andrews: Geology of Ohio, Vol. II, 1874, p. 441. J_ <v ^/. 2 I o J MIDDLE OHIO DRAINAGE SYSTEM. 107 How much of the present Ohio above the jaoint where Teays Valleyconnects with it follows its old course may now be considered. Betweenthe present mouth of the Kanawha, at Point Pleasant, W. Va., and thewest end of Teays Valley, the Ohio is in a valley which for a few milesbecomes so constricted as to suggest the crossing of an old divide. Thewidth at Point Pleasant is about 2 miles, but it becomes reduced to 1J milesin the first 8 miles below that town, and to scarcely 1 mile at Crown City,10 miles farther down. For 10 miles below Crown City the breadth is amile or less. The valley then gradually expands to a width of nearly 2miles at Huntington, 15 miles farther down the river. In this narrow por-tion the bluffs rise abruptly to a height of 200 feet, or to about 700 feetabove tide, and the uplands reach an altitude 200 feet higher within a mileor two of the river. A thick-
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectgeology, bookyear1902
