Page:Report on the geology of the four counties, Union, Snyder, Mifflin and Juniata (IA reportongeologyo00dinv).pdf/280

252 F³. This slate in its turn is overlaid by a siliceous “cement rock,” 10′ or 15′ thick, which at one time was quarried by Mr. Stratton for the purpose of producing fire-brick, Although this material made a good clay, the fire-brick resulting from its burning was found to contain too large a percentage of sand mechanically mixed through it, so that in a hot fire the bricks were apt to run.

A small thickness of gray slate overlies this rock to a shallow and tight synclinal basin of only local importance, reversing the dip to 70° southeast. A small anticlinal roll succeeds this going north along the pike crested mainly by the cement rock, but exposing a little of the underlying black slate. The dips here are 25° to the N. W. 70° to S. E,

This synclinal basin of VIII is succeeded by a narrow strip of the Oriskany sandstone measures approaching the Mt. Rock G. M., showing dips of about 50° to the southeast and at the mill, by an excellent exposure of the Lewistown limestone and shale.

A narrow anticlinal valley of the upper Salina shales succeeds the limestone going towards Logan, and they in turn sink beneath synclinal of limestone making the middle of the three limestone ridges between Lewistown and Logan and capped by isolated areas of the Oriskany sandstone.

This hill is synclinal in structure, like that at Logan, and between them there is an eroded valley of the upper Salina shales and marls which create a very fertile belt of farm land passing right through the center of the township.

The Logan synclinal holds only limestone at the creek; eastward, as the basin deepens, the hill splits first to receive a central ridge of Oriskany sandstone which in its turn is divided to receive the narrow tongue of Marcellus slates in which the Townsend iron mine is situated.

It is almost impossible to describe minutely the various structural features of the valley here, for there are many subordinate flexures which are wholly of a local character, but which for a space exercise a very important influence in affecting the economical features of the township. With the colored map in hand, however, and an inspection of the dip-arrows, it will be readily seen how the same rocks are