English: Harpers phyllite thrust northwestward over Ledger dolomite at left, in small roadside quarry on Pottery Hill, southwest of York. York County, Pennsylvania. Exposed fault plane dips 55° SE. Circa 1930. Plate 18-B, U. S. Geological Survey Professional paper 204, Geology of the Hanover-York district, Pennsylvania by A. J. Stose and G. W. Stose. 1944.

Text of the publication refers to the figure:

An anticline marked by a belt of hills composed largely of Kinzers formation extends from Spring Grove northeastward for 6 miles and is called the Sprenkel School anticline. It divides the limestone area of the valley southwest of York longitudinally into two narrow lowlands. Along the axis of the fold, Vintage dolomite comes to the surface at two places, one northeast of Spring Grove, and the other north of Sprenkel School. The lower shale member of the Kinzers formation, exposed in rows of low hills, entirely surrounds the dolomite; and the ends of the fold pitch steeply northeastward and southwestward. Along the Gnatstown overthrust, the Kinzers formation on the north flank of the anticline overrides the Ledger dolomite and Conestoga limestone. South of West York, the small Pottery Hill anticline lies north of the east end of the Sprenkel School anticline. The axis of the Pottery Hill anticline trends east; and Harpers phyllite in the core is surrounded by Antietam quartzite, with Vintage dolomite on the southeast flank. This anticline is cut off on its west and north sides by the Gnatstown overthrust. The thrust plane is exposed in a small quarry on the south side of Lincoln Highway (U. S. 30) where it crosses Pottery Hill 1 mile southwest of West York. In the quarry the thrust plane dips 55° SE., and Harpers phyllite is thrust on Ledger dolomite, which makes the lowland to the northwest. (See fig. 23 and pl. 18, B.) Northeastward the Gnatstown overthrust is not clearly traceable in the city of York, but a possible further extension of the fault is discussed in connection with the Mount Zion anticline.