Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/397

Rh anticlinal which has nowhere been strong enough to bring up the Oneida sandstone measures.

A superb view of the entire Tuscarora valley, as well as the anticlinal mountains forming its northern border lines, can be obtained from the north terrace-of the Tuscarora mountain on this road; and though the laborious trip up its steep flank is rendered geologically unsatisfactory by the poor rock exposures, this view will well repay tourist or scientist who wishes to get an idea of the topography and structure of the Juniata district.

The Ore sandstone and Iron sandstone show but a single outcrop in these two townships, extending east and west as a high unbroken terrace along the north flank of the Tuscarora mountain. Very little, if any, development has ever been attempted, and what little has been done has been mainly near the Juniata river, where the Sand Vein fossil ore bed is reported to be from 8″ to 12″ thick. Various efforts have been made from time to time, in a perfunctory manner, to locate the Sand Vein or Danville ore beds further west along the mountain range; but the terrace ridge is so completely covered with bowlders of all sizes of white Medina sandstone fallen from the mountain further south, that the task is an exceptionally difficult one, especially so in the face of the uncertain character of the ore and the disadvantages of getting it to market if found.

A most conspicuous feature of the district lying along the base of the Tuscarora mountain is a narrow synclinal basin of limestone, known as the “Sink Hole valley” from the fact that many of the mountain streams upon reaching it sink and pass underground to the river.

This little valley extends west from the river for about 5½ miles, or about to the mountain road to Perry county near which several large sink-holes serve to locate its position. Few, if any, limestone outcrops are actually seen, but a great number of sink-holes of all sizes and shapes serve to locate the limestone which is itself practically concealed everywhere.

In Spruce Hill township the synclinal still exists between