Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/371

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This township extends from the crest of the Tuscarora anticlinal ridge on the south to Fayette township on the north. Greenwood bounds it on the east and Walker on the west. Its shape is somewhat irregular, by reason of the offset in the Perry county line passing from the spur the Tuscarora mountain at the Juniata gap northward for 1½ miles to the crest of Turkey ridge, along which it runs for a mile to the Greenwood township line. The east line is straight and a common one with Greenwood and Monroe, about 4 miles in length from Turkey ridge on the south to the Birds run summit on the north. The west line has one break extending 3½ miles from the crest of the Tuscarora mountain across the Juniata river valley to the Oriskany sandstone ridge of the north leg of the main Tuscarora synclinal; and with a slight angle extending 2 miles further from that ridge to the summit of Flintstone ridge on the Fayette township line. The area approximates 30 square miles.

Cocolamus and Delaware creeks drain the entire township, with the exception of its lower portion, which is drained directly by the Juniata river. Thompsontown and East Salem are the principal villages.

The rock section exposed extends from the red and white Medina sandstone in Tuscarora mountain to the Hamilton rocks of No. VIII in the Tuscarora and East Salem synclinals between the zigzag outcrops of the Oriskany sandstone and Lewistown limestone in the ridges flanking these two principal slate valleys.

The Medina white sandstone No. IVe, which makes the Tuscarora anticlinal, is nowhere well exposed. Even at the magnificent gap made by the Juniata river its rock is so broken down as to conceal all evidence of the beds in place; but the arch must be rather flat at the river with dips of not over 45°. Westward they stiffen somewhat as the ridge rises in elevation, and at the same time, 1½ miles east of the Walker line, the anticlinal splits to receive a narrow tongue of the red Medina No. IVb.