Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/105

Rh On Big Run, at the gap through Slenderdale ridge, the Ore sandstone is exposed in the south anticlinal in a broad arch 60′ above the creek, 25′ thick in thin bands, with dips of 5° S. E. 20° N. W. Some abandoned ore-diggings were seen between the anticlinal and the north axis of the ridge in the shales above the Ore sandstone, a rather unusual horizon and one which does not seem to have yielded very satisfactory results here. It is said to have shown about 2′± thick; but carried Jack mixed with it. It has a sandstone floor and dips gently southeast; while above the opening, on the hill, the same ore is said to have been struck in a shaft on a north dip, yielding 12″ of good ore. The exact horizon of this bed is obscure.

West of the Juniata river, the Clinton rocks occupy the Jong and narrow valley of Licking creek, between Blue Ridge and West Shade mountain, and deepening towards the Juniata it receives a narrow strip of the upper Salina lime shale Vc′, with Jack. On the south flank of the Blue Ridge the Sand Vein has been opened 18″ to 2′ thick, dipping S. 15° E. 40°.

The Black Log axis to the south elevates the Ore sandstone with its fossil ore in a double outcrop; while the succeeding basin deepens to receive all the Salina and part of the Lewistown limestone groups. Between this basin and the main Tuscarora synclinal, the Academia anticlinal, crossing the Juniata about midway between Mifflintown and Port Royal, elevates there the Ore sandstone, and increasing in strength rapidly westward pushes the two outcrops asunder, until at Academia they are a mile apart. From this point they gradually converge toward a common meeting point near Reed’s gap.

Between these two ridges, there is a wide elevated plain of the lower Clinton rocks exposed, in which the Iron sandstone outcrops in two parallel hills, within those of the Ore sandstone, while the western part of the county, west of Reed’s gap, is largely occupied by the middle and upper lime shales and olive shales of the Clinton group.