Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/289

From Wikisource
Jump to navigation Jump to search
This page has been proofread, but needs to be validated.
30.Derry in Mifflin.
F³. 261

Henry Stein and Thomas Arnold have opened quarries on the last (25°) rise and on the east side of the public road. The former was temporarily abandoned; but the latter quarry was being actively worked and displayed two principal divisions, an upper gray and rather siliceous limestone 20′ thick, and a lower dark blue limestone, some of it showing a conchoidal fracture, in all 70′ thick, in beds from a few inches to several feet thick. The burned stone from this lower division is largely used for plaster lime and fertilizing purposes. Mr. Arnold stated his output at from 20 to 25 thousand bushels per year, using a ton of pea coal for every hundred bushels of lime. The prices during last season were 6 cents. “for run of quarry” stone and 10 cents for “screened lime.”

There is no Oriskany sandstone capping the ridge at this point and no evidence of it in the gap, and if it exists at all it is entirely as shale. The limestones make a fine bluff on the south side of the ridge facing the railroad, and are underlaid by some buff-colored magnesian limestone. The upper Salina marls and shales occupying the valley of Jack’s creek through which the railroad runs.


Going north from the Dunkard church in the valley, the synclinal is well marked by outcrops of brown ferriferous shales (No. VIII) just above the brick school-house with converging dips of 60°. North of this the road bends sharply eastward around the point of a narrow ridge, showing thin bedded but hard gray sandstone belonging to the Hamilton division dipping 80° to the southeast, and creating quite a terrace ridge upon the flank of the Oriskany ride to the north.

The Marcellus slates lie between these two ridges. In ascending the plateau which they create, outcrops of the Marcellus limestone and some little hematite ore were noticed, corresponding geologically to the Townsend ore located in the next valley to the north. The Oriskany sandstone in this hill, which is known locally here as the “Flagstone ridge” is considerably iron-stained, and rather coarse grained. The Lewistown limestone and the upper