Description of the Geology of
Beaver County
Pennsylvania

 
Beaver.- Area, 450 square miles; population in 1880, 39,605. The Ohio river makes a great sharp bend across this county, the Beaver river meeting it at the point of the bend, after cutting a long straight gorge through nearly horizontal (gentle south dipping) Pottsville Conglomerate No. XII massive sand-rock strata, supporting an upland of Lower Productive coal measures, of which the Freeport and Kittanning coal beds, the ferriferous limestone, and the Clarion fire-clay, are the most valuable layers. All the hill-tops north of the Ohio river are of the Barren measures. South of the river the country is made by the 600 feet of Barren measures; but the Pittsburgh coal bed is left in a few of the highest hill-tops near the Washington county line. The outcrop of the Ferriferous limestone appears above water level at Freedom and extends down the Ohio and up the Beaver to the county lines; and up Connoquenessing creek for three miles. At Darlington the Middle Kittanning coal becomes nearly 20 feet thick, by the conversion of a part of its roof shales into cannel coal. Before the discovery of petroleum in 1859, oil was manufactured from these shales; and they have yielded to Mr. Mansfield's intelligent and zealous research an incredible number of fine plant-forms described in the Coal Flora, Report P, by Leo Lesquereux, and of crustaceans described in Report P³, by James Hall. A considerable amount of petroleum was at one time obtained, by wells near the State line, both from the Conglomerate No. XII, the top of which is near river level, and from oil sands at the greater depths of 500 and 600 feet. Glacial drift covers the north-western corner of the county, the great Terminal Moraine passing north of Galilee along the highland north of the Little Beaver. The drift materials were swept into the deep slackwater pool of the Ohio and Beaver valleys during the continuance of the Cincinnati ice-dam; and relics of the deposit have been preserved in four lines of gravel, sand, and brick-clay terraces, at heights of 30, 80, 125, and 215 feet above the river bed at New Brighton; these support a large manufacture of pottery and fire-brick. (See Report Q.) 

From: A geological hand atlas of the sixty-seven counties of Pennsylvania :embodying the results of the field work of the survey, from 1874 to 1884. By J. P. Lesley. (Report of progress (Geological Survey of Pennsylvania), v. X ) Harrisburg, PA : Board of commissioners for the second geological survey, 1885.

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