The formations that have been grouped as the “Glenarm Series” consist of phyllites, schists and gneisses with subordinate amounts of quartzite and marble. Within this series, a general, though by no means regular, increase in intensity of metamorphism toward the east and south has long been recognized; several authors have published small-scale maps, some based on texture and some on mineral distribution but without defnite mineral isograds.

The main feature of the present paper is a map (in two sections) of the area covered by the Philadelphia and Coatesville-West Chester Folios showing reported and observed occurrences of index minerals. In the argillaceous rocks the zonal arrangement: chlorite, biotite, garnet, staurolite, cyanite, sillimanite is in accord with observations in metamorphic areas in other parts of the world. The zones are somewhat crowded and show local overlapping. In the associated carbonate rocks, tremolite appears in the middle-grade zone and sparse pyroxene in the highest grade attained. Wollastonite and garnet have not been reported in the carbonate rocks.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.