Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/237

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23.Perry Township in Snyder.

F³. 209

23, Perry township in Snyder county.

This township makes an irregular area of about 25 square miles lying west of Washington and Chapman townships and between the West Mahantango creek and the Medina erest of Shade mountain. Its western line, in common with West Perry township, is a straight one 5 miles in length between the mountain and the creek, and its north line along the mountain is also straight and 2 miles in length. Its eastern and southern lines however make many angles, the former cornering first on the Ore-sandstone ridge ; then on the Hamilton ridge east of Mt. Pleasant mills ; and then on the Chemung sandstone ridge 4 miles west of Port Trev- orton. Here it makes aright-angled bend and extends to Mahantango ereek north of Meiserville, following that stream to its forks, abont 14 miles from the river.

Mahantango creek carries away the entire drainage of the township south and eastward into the Susquehanna river, the west branch dividing the township from Juniata county, and the east branch flowing through it from the Klopper- dale valley on the north to below Meiserville on the south.

Freemont is a beautifully situated village in the northern part of the township, located in the Shamokin synelinal between walls of the Oriskany sandstone of the Firestone ridge.

The structure of the township consists of the Shade mountain anticlinal which marks its northern line, from which the rocks dip southward in successively higher strata to the Firestone ridge north of Freemont. The Shamokin synclinal passes through the town and has become so shallow here as to contain only the Marcellus black slate of No. VIIL.

The rapid rate at which this synclinal axis rises coming westward may be inferred from the fact that on the river, onty about 8 miles east of Freemont, it contained in addi- tion to the entire No. VIII formation, at least 3500’ of No. LX, so that at Freemont over 7000’ of these rocks have been eroded.