328 F. BASCOM — PIEDMONT DISTRICT OF PENNSYLVANIA 



hickon mica-schist, place in question the equivalence of the Wissahickon 

 mica-gneiss and the Wissahickon mica-schist. 



If the former formation should prove to be faulted on the latter forma- 

 tion with a low southeast hade, and if the apparent superior position of 

 the Wissahickon mica gneiss on the Chester Valley limestone be due to 

 overturned synclinal structure — a possibility which the writer recog- 

 nizes — the Wissahickon mica-gneiss will be shown to be pre Cambrian 

 in age. Detailed work in areas not yet mapped will be necessary in 

 order to establish the Ordovician or the pre-Cambrian age of the Wissa- 

 hickon mica-gneiss. 



