116 PROCEEDINGS OF THE ACADEMY OF [March, 



County; Boyertown, Berks County; south of Reading, on the 

 Schuylkill; Cornwall, Lebanon County, and on the west bank 

 of the Susquehanna below New Cumberland. The writer's studies 

 have not been extended southwest of the Susquehanna River, 

 but Mr. George W. Stose, of the U. S. Geological Survey, who has 

 traced the line through the Fairfield Quadrangle, states (private 

 communication) that overlap relations occur there also. 



The exposures at Monroe, a small village on the west bank of the 

 Delaware River along the Easton-Philadelphia trolley line, nine 

 miles south of the former place, have been studied and described 

 by Dr. H. B. Kiimmel.^ The Brunswick conglomerate appears 

 to overlie a bluish-gray (probably Cambrian) limestone, although 

 the actual contact is covered by talus, and he regards it as probable 

 that overthrust faulting has occurred. There is admittedly no 

 direct evidence of this, but even if it does exist, it must be of very 

 limited extent, and can have no bearing on the relation of the 

 formations as a whole, because the fault-boundary shown in Section 

 A would be of normal type and many thousands of feet in throw. 

 About 500 feet south of the first exposure a ledge of white rock 

 appears at the base of the trolley cut, and is solidly overlain by the 

 Triassic conglomerate. This may represent only a local phase 

 of the Triassic itself, and, if so, has no significance, but it may also 

 possibly be pre-Triassic limestone, in which case the existence 

 of a fault is out of the question. 



About a mile and a half southeast of Spring-town, Bucks County, 

 five miles southwest of the Delaware, what appears to be a contact 

 is exposed in the bed of a brook. A rounded ledge of a yellowish 

 quartzite similar in all respects to the Cambrian (Hardyston) of 

 the region, at least 12 feet long and 4 feet wide, shows fragments of 

 typical Triassic conglomerate solidly welded to it. It is true that 

 neither rock can be traced to solid connection with the main ex- 

 posures in the vicinity, and the quartzite may not be in place, but 

 it is too large a mass to have been carried far. 



For some twenty miles southwest of this point nothing that can 

 be regarded as. a definite contact has been discovered, and there are 

 reasons for believing that locally slight faults occur, but at several 

 places in the vicinity of Boyertown, Berks County, overlap re- 

 lations are again shown. As noted by Dr. Spencer,^ along the road 



'^Ann. Rept. State Geol. N. J., 1897, pp. Ill, 112. 



5 Magnetite Deposits of the Cornwall Type in Pennsylvania, Bull. U. S. 

 Ceol. Surv., No. 359, p. 64, 1908. 



