514 STOSE AXD JOXAS OEDOVICIAN IX PIEDMONT PROVIXCE 



Leaman Place, limestone conglomerate and associated slaty limestone of 

 the Conestoga rest on the Vintage dolomite (see figure 8). Although 

 the Kinzers formation is fully exposed in the Pennsylvania Eailroad cut 

 just to the north, the Conestoga is nowhere seen resting on the Kinzers. 

 This overlap is apparently concealed by a thrust-fault that passes between 

 these two exposures. 



A little farther south, on the north flank of the Mine Ridge anticline, 

 the Conestoga almost completely overlaps the Vintage dolomite, and on 

 the south flank it entirely overlaps the Vintage and rests on Harpers 

 schist. The Conestoga limestone north and east of Quarryville has been 

 recrystallized into compact gray and white banded micaceous marble, 

 which is closely folded and fluted (see figure 10). The local extreme 

 anamorphism is described by E. B. Knopf ajid A. I. Jonas in a 23aper on 

 the Quarryville region.^ 



The Conestoga limestone covers the whole floor of Chester Valley from 

 its southwest end, at Quarryville, nearly to Coatesville. East of Coates- 

 ville it is restricted to the southeast side of the valley, and the Cambrian 

 limestone formations appear one by one toward the northeast, progres- 

 sivel}^ emerging from beneath the overlapping Conestoga (see map, 

 figure 12). East of Downingtown the overlapping limestone is locally 

 preserved in a narrow synclinal fold in the middle of the valley where it 

 retransgr esses the boundaries of two of the higher formations (see map, 

 figure 13). The Conestoga here is not so greatly metamorphosed and is 

 made up of conglomerates interbedded with argillaceous, somewhat 

 micaceous, limestone and thin graphitic slates. Still farther northeast 

 the Conestoga limestone occupies only a small southern part of Chester 

 Valley, the Cambrian formations occupying the larger northern part, 

 ^ear the Schuylkill Eiver the Conestoga apparently overlies the Beek- 

 mantown limestone, but this area has not been studied in detail by the 

 writers. 



West of Lancaster the Conestoga gradually overlaps the Ledger dolo- 

 mite and rests on the Kinzers formation, and further west on the Vintage 

 dolomite. It forms almost the whole of the limestone valley around 

 Columbia, only a narrow band of the Vintage lying between it and the 

 Cambrian quartzite and schist of the Chestnut Hill anticline on the north 

 and of two anticlines of the Harpers schist on the south. Limestone 

 conglomerates here persist as an integral part of the basal beds of the 

 Conestoga and are finely exposed in the Wrightsville quarries. Certain 

 peculiar blue and black earthy shales and sandy beds that appear near 



3 Am. Jour. Sci.. 5th ser.. vol. o, January. 1923, pp. 59-61. 



