File:Bulletin 799 Plate 5B Folded Conestoga Limestone.jpg

English: Figure caption: Closely Folded Micaceous Marble of Conestoga Limestone in quarry half a mile northwest of Quarryville.

The text of the report referring to the figure is as follows:

Southward from the northern edge of the district to the Mine Ridge anticline there is a gradual increase in the metamorphism of Paleozoic sediments and consequently of the Conestoga limestone. South of Bunker Hill, Refton, and Marticville the Conestoga limestone is a coarsely crystalline marble with considerable brown mica developed on the partings and throughout the rock. It is closely folded and crumpled and converted to a crystalline schist, like the underlying Harpers and Antietam schists. West and south of the Mine Ridge upland the metamorphism and folding have been most intense, so that no individual beds of the Conestoga can be traced any distance and no sequence can be determined. Recrystallization has obliterated all trace of limestone conglomerate beds and produced a series of gray and blue marbles in which the slate beds have been altered to micaceous banded marble. (See pl. 5, B.) The mica in this marble is phlogopite. There are many good exposures of micaceous marble, highly folded or crumpled, in cuts of the Atglen and Susquehanna branch of the Pennsylvania Railroad north and east of Quarryville and for 2 miles east of Shenks Ferry. Here beds of marble and siliceous marble alternate with beds of micaceous calcareous schist. Cleavage diagonal to the bedding, which is marked in the micaceous layers, is absent in purer marble beds made up of calcite and without the platy mineral, mica.