Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/374

346 F³. are succeeded in about one-half a mile by an outcrop of the lower Hamilton shale and sandstone, making a tightly compressed synclinal, with dips of from 60°–80°. It shows a somewhat unevenly bedded grayish-white sandstone 30′ thick, important as being the only suitable sandstone occurring in this vicinity for paving and building, for which purposes it has been largely used at Thompsontown. The outcrop is somewhat twisted, especially in the south dips, showing well in the brown slates overlying the sandrock. The structure north to the base of the Oriskany sandstone ridge at the school house is probably complicated by several sharp but local rolls; for a gray sandstone ledge very like the one just described is seen at many places to and beyond the old stone grist mill.

The Marcellus black slate is well exposed just below the school house dipping S. E. 20° in the north leg of the Tuscarora synclinal. Its low dip carries it forward nearly to the school house where a band of the Marcellus limestone shows overlying the chert. It is greenish-blue in color; slaty, ferriferous and about 15′ thick.

North of the Academia anticlinal in the East Salem basin, the road and the hills on either side of it north of the brick church are composed, first of the Marcellus slate, quickly succeeded by the lower Hamilton shales and a considerable thickness of the Hamilton gray sandstone, weathering brown and dipping 40° N. W. At East Salem the Genessee slates with the upper Hamilton shales outcrop on 35° N. W. dips and extend east and west through a branch valley of Delaware run into Walker township.

These rocks form the synclinal, the axis of which is but a short distance north of East Salem. Between the basin and Flintstone ridge the same measures are repeated only on reversed (southeast) dips. The Hamilton sandstone creates a sharp ridge just north of the forks of the road at Mrs. Fry’s dipping 30° S. E. and between this ridge and the Flintstone ridge the Marcellus shales outcrop.

Along Cocolamus creek the same section of rocks (somewhat amplified by reason of the increasing depths of the Tuscarora and East Salem basins) is exposed between Turkey