Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/59

Rh, with the Havise valley on the north and the New Lancaster valley axis on the south.

The slates of No. III occupy the Triester valley and crest of the axis from the Union county line west for 6½ miles, where the Siluro-Cambrian limestone No. II is elevated to the surface, about 2½ miles east of Siglerville. At the latter village the axis throws off dips in this limestone of 60° north and 70° south. The axis shows on the Lewistown and Bellefonte turnpike, about a mile below Milroy, with dips of 40° and 60°, therefore flattening gradually westward. On Tea creek in Brown township, less than 3 miles further west, the axis is normal and shows dips of but 30°.

A little south of Barr’s P. O. in the same township, the axis is represented by a close fold in the limestone with dips of 80° each way; but the south dips almost immediately flatten down to 5° while the north dips hold up to 50° and 60°. This point is almost immediately south of the fracture in the mountain, which results in the faulting and shoving of the mountain rocks as already described.

The anticlinal can be traced four miles further, into Union township, making a hook in the outline of the slate outcrop north of Mechanicsville. West of this point it is overriden by the greater strength and effect of the Stone Mountain fault. This fault, unlike that of Brush ridge in Brown township, shows only a lateral thrust, causing a breaking in the Stone mountain along a N. 33 E. line, which has swung the two ends of the mountain past each other for about a mile in distance, duplicating the rock measures on either side of this fault so that in going in a northwest direction from Mechanicsville to Huntingdon county, one passes over four ridges instead of two, Standing Stone mountain being a double monoclinal ridge with north dips. This great fault, one of the most interesting in Pennsylvania, is distinctly shown on Mr. Billin’s map and has been minutely and graphically described by Prof. Lesley in the Huntingdon county report, Vol. T3, p. 337.

The coloring of the county map will also sufficiently show the effect of this fault, as well as the curious modifications of dips near the line of thrust, displayed in the