Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/243

Rh The Shade mountain anticlinal begins to develop rapidly in the northeast corner of the township, and after lifting the red Medina No. IVb to daylight on its crest for a little over 3 miles, it brings up the Oneida sandstone and con- glomerate No. IVa, splitting it in turn 3 miles from its first appearenceappearance [sic] to admit of the Hudson river slate No. III valley, which extends for 4 miles to the Juniata line between opposing walls of the Oneida sandstone.

The crest of the arch through this slate valley is evidently very flat, for along the road leading over the mountain from Adamsburg to McAlisterville two small detached knobs of the bottom Oneida conglomerate remain near the Juniata county line to attest the former continuation of the unbroken arch across this slate valley, which has now been generally eroded 200′ or more beneath the enclosing crests.

This feature is exceedingly interesting and rare, and is illustrated upon the colored county map.

The Shamokin synclinal continues as a narrow basin west of Freemont, holding along the Perry township line, a small wedge of the Marcellus slate, west of which the enclosing walls of Oriskany sandstone extend a little over a mile from the eastern line to end in a high spur along the road crossing this ridge to Hannibach creek. The ridge itself is continued for 2 miles further west, but now totally occupied by the lower Helderberg limestone until at the M. E. church north of Richfield the limestones in turn are eroded, and the synclinal becomes very faintly exposed in the upper Salina lime shales of Hiester valley.

The Slenderdale anticlinal lying immediately south and along the Perry line quickly elevates the upper Salina lime-shales on its crest, curving gradually northwards towards the Shade mountain and along the Juniata line brings up a narrow strip of the lower Salina or Bloomsburg red shales on its crest for 2 miles before leaving Snyder county. All the rocks south of this line dip southeast, bringing down in turn No. VI, No. VII, and the bottom of No. VIII.

The rock section, therefore, extends from the No. III slate in the Spiegelmeyer valley upwards to the Hamilton slates and sandstone, and possibly a little Genessee on Mahantango creek.