Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/169

Rh fossiliferous layer, 10′ in thickness. From this bed to the top of the Salina there is a section of gray and dark blue limestone beds, about 220′ in thickness, of which only the bottom 125′ contain the massive good beds of the Lower Helderberg formation; but even thus reduced, the entire series seems to be thicker here than almost anywhere else in the vicinity and certainly much increased over the same series of rocks exposed further west in Snyder county.

Higher Hamilton beds are seen to the north in the vicinity of Shamokin dam above which place they begin to make cliffs and high land composed of dark brown and olive shale and thin sandstone beds on dips of from 30°–55° N. W.

Shamokin Falls in the river are created by a ledge of this Hamilton sandstone, 4′ or 5′ thick, which was used to construct the canal dam upon.

The Genessee, Portage and Chemung rocks at the top of No. VIII which occur between Shamokin dam and the bottom red layers of the Catskill formation are fairly well exposed on 60° N. W. dips. The Genessee shales do not show any outcrops in place, being largely soft yellow slates yielding readily to erosion. The Portage rocks were not independently distinguished, unless they occur in the high bluff at Clement Station, opposite the west end of the Philadelphia and Reading railroad bridge.

From this point northward to the Catskill rocks there is one of the finest exposures of the Chemung No. VIII rocks in the district. There is scarcely a break in it down to within a mile of the Shamokin dam, the rocks everywhere creating high bluffs and showing a constant succession of shales, slates and gray and brown sandstone beds on an average dip of about 60° towards the northwest. A computed estimate of the No. VIII series hereabouts would assign at least 3500’ of thickness to the entire series.