Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/235

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22.Chapman Township in Snyder.

F³. 207

located, owing to the great erosion of the measures in the south leg of the synclinal facing the river; but it cannot be far sonth of the first dwelling house met are south of the aqueduct, inasmuch as occasional ledges of rock seen going further south, show steep northwest dips. There are good exposures however between the two roads leading west and at Witmer’s store, where shale and sandstone dip 45° N. 15° W.

In a short 4 mile south the rocks begin to lose their red color in the transition Catskill-Chemung rocks, which ap- pear on dips of N. 20° W. 50°. Here the limit of the Cats- kill rocks may be placed, assuming their base to be fixed at the lowest red beds seen.

The Chemung rocks to the south, extending down nearly to Port Trevorton, are quite shaly and iron-stained, and occur on steadily declining dips of from 35°-15°, and with a thickness of about 2000’ including the Portage division. They are well exposed and make a practically continuous section, consisting of five or six hundred feet of greenish- olive shale on top, and a succession of gray, green and brownish sandy-shale beds, 1400 or 1500 feet thick at the bottom, which beds west from the river are responsi- ble for the ridge-land characterizing the topography of this township.

A section of the stream from Chapman to Port Trevorton shows first some grayshales occupying the crest of a small anticlinal, with dips of about 35° each way, gradually de- clining northward to Rhinehart’s house, where the syneli- nal occurs with northwest dips of only 10°, and southeast dips of 60.° These are largely the lower Chemung and Gen- essee shales, the latter just coming to daylightat Port Trey- orton, where anticlinal reverses the dip and brings in the Chemung rocks going north.

The Marcellus black slate is well exposed near the forksof Mahantango creek in the south end of the town- ship ona dip of 40°-35° N. 12° W. Opposite the mill and north of Arnold’s blacksmith shop, there is a fine exposure