Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/380

352 F³. East and west of the Evangelical church the Marcellus slates outcrop (VIII b) within 100 yards of the road, to the entire exclusion of the limestone and sandstone ridge.

The narrow valley in which Mexico is located is composed of the Marcellus slates and the lower Hamilton shales, very little evidence of the Hamilton sandstone existing far beyond the Delaware township line.

Just north of Mexico, and immediately back of the brick schoolhouse, these slates are largely quarried from time to time for road use at J. M. Thompson’s quarry. The opening is largely in the lower Hamilton shales, brown and buff colored, with some thin bands of sandstone, which, near the base of the exposure, aggregates 12′ or 15′ in thickness and has been used in Mexico for building and bridge purposes. The dip is 30° S. E.

The East Salem synclinal on the south side of Flintstone ridge is almost wholly occupied by the Marcellus black slate.

These two townships can be conveniently described together, as they make a roughly rectangular area, comprising about 50 square miles, lying west of the Juniata river and north of Tuscarora creek. The north line of Milford township, as well as the Juniata-Mifflin county line, runs west along the south (Medina) crest of the Blue ridge for about 8½ miles, having a slight offset one-half mile long at the eastern end of the mountain passing to the Juniata river in the “Narrows.”

The western line of both townships is a straight one about 5 miles long, extending from the Blue ridge at Minehart’s gap southeast to the Tuscarora creek near the center of the Tuscarora slate valley. The Tuscarora creek forms the southern boundary everywhere, except at the great Horse-Shoe bend, south of Academia, where the line runs along the north Limestone ridge for nearly a mile.

Milford township has an irregular offset comprising the Licking creek valley area between Blue ridge and the West Shade mountain. The latter mountain forms the line be-