Salina shales occur along its north flank and about a mile to the east fold over the anticlinal axis as before described, subsiding there beneath a high knob of the Oriskany sandstone east of Stroup’s place.
31. Granville township in Mifflin county.
This township lies immediately west of Derry and with some minor differences simply continues its geology westward.
Jack’s mountain forms its northern boundary for 6 miles and Blue Ridge its southern boundary for about 8½ miles.
The Juniata river divides Granville and Derry townships from the county line as far west as Lewistown, and from that point north to Jack’s mountain these two townships have a common dividing line.
The western line is somewhat irregular. Leaving the Medina crest of the Blue Ridge near Minehart’s gap, the line is a straight northwest one for 2 miles to the Juniata river a short distance west of Anderson station. Thence it follows down the river a short distance to the mouth of Strode’s mill run, thence following that stream north for about 2 miles to the crest of the third Oriskany ridge north of the Lewistown and MeVeytown pike. From the summit of this ridge the line is again straight for nearly 2 miles to the summit of Jack’s mountain at the Belleville road.
Its area may be roughly set down at 40 square miles, averaging a little over 6 miles each way.
The Juniata river flows sinuously through the southern portion of the township in a fertile plain of Salina rocks.
Strode’s mill creek, rising in the Ferguson valley ore ridge, flows directly across the measures to the river at Lockport.
Ferguson valley, like the valley of the Juniata, is composed of the lower and upper Salina measures, largely lime-shales and marls, but containing a number of thin bands of red shale, especially in that portion nearest the base of the Ore Ridge.
