Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/373

Rh posite this across the valley in the north leg of the north anticlinal, where the dip is 30° northward in corresponding limestone measures. Both quarries are worked merely for farm use. The massive portion of the Lewistown limestone formation does not appear to be so thick nor to contain as good beds as it does in Mifflin county, but the lower portion of the formation, as well as the top members of the upper Salina group, are much more calcarous and often contain beds of sufficient thickness to warrant their being economically worked. These same characteristics prevail through the synclinal occurring between these two outside ridges along Delaware run.

Smith and Keyser’s quarry, situated on the west side of Delaware run about a mile south from East Salem, shows about 30’ of the same dark blue limestone, with a peculiar conchoidal fracture and dipping only 10° N. W. in the south leg of the synclinal. The good limestone is overlaid with 15′ of shaleyshaly [sic] impure limestone which extends to within a few feet of the surface There are two kilns here burning limestone for farm use, which obtains a ready sale through the slate valleys to the east of this point.

The Oriskany sandstone in these ridges seems to be entirely chert, making two flat hills extending for nearly a mile east of Delaware run, the southern one being slightly the longer and higher. The same cherty character of rock occurs in the main Flintstone ridge, lying north of the East Salem slate valley ; while the southern ridge, flanking the Tuscarora valley on the south and virtually extending Turkey ridge westward through Thompsontown to the river below Mexico, is covered with the same chert wherever the ridge has not been entirely eroded. In this southern ridge the limestone is nowhere quarried, making a very uncertain and interrupted outcrop and nowhere very massive.

North of Thompsontown, along Delaware run, this ridge is completely eroded and the occurrence of chert and limestone can only be inferred from the character of the soil and the records of well diggings in the village.

The Marcellus slates outcrop a little further north, and