Page:Origin of the High Terrace Deposits of the Monongahela River.pdf/7

374 Fairmont and Palatine at the junction of the Tygart's valley and West Fork rivers, 26 miles above Morgantown, are situated on the wide plain excavated by the pre-glacial river, and as might be expected, the old rock floor is covered to a great depth with terrace deposits, consisting of sand, rounded boulders, etc., from the Tygart's valley, and pottery clays from the West Fork river. The elevation of the old rock-floor is 972.5 feet A. T., or 122 feet above the present river, while the top of these deposits extends up to 1,067 feet A. T.

The terrace material at Fairmont has been well exposed along Fairmont avenue, and its stratified condition is well shown. At the Smith & McKinney building the excavation showed the ditferent stratified layers of sand and clay dipping about 10^ to the west.

A layer of clay, about eight feet thick, at near 1,000 feet A. T., has long been mined for pottery clay, in the Fairmont region. The corresponding bed at Morgantown has an elevation of 945 feet A. T.

At Clarksburg, thirty miles above Fairmont, the West Fork river is joined by a large tributary, Elk creek, and the two streams had carved out a wide valley in pre-glacial time, whose rock-floor under the city has an elevation of 986 feet A. T., or about 70 feet above low water (916 feet A. T.) at the junction of Elk and the West Fork rivers. Here a great deposit of clays and quick-sand, twenty-five feet thick, covers all the level surfaces up to 1,020 feet A. T. There are some layers of rather coarse sand in the deposits, but the clays predominate, and they are found all along the West Fork river, and its tributaries from Fairmont to Clarksburg and on beyond to Weston, thirty miles south, where they extend to only about thirty feet (1,020 feet A. T.) above water level (990 feet A. T.).

At Grafton, on the Tygart's valley river, twenty-two miles above Fairmont, the elevation of the top of the railroad pier in the river is 997 feet and the terrace deposits extend only about twenty-five feet higher.

The principal town sites along the Monongahela river from Weston to Pittsburg, viz: Weston, Clarksburg, Grafton, Monongah, Fairmont, Palatine, Montana, Morgantown, Point Marion, Geneva, Greensboro, Rice's Landing, Fredericktown,