18 



GEOLOGY. 



than Jurassic. The physical relations of the Newark beds to the 

 Cretaceous show that before the deposition of the latter, the former 

 had been uplifted, tilted, faulted, and subjected to a period of erosion 



rr°4o 



Newark System. 



Diabase Coal Measures Vinita Group. 



Dikes. and Lower Sandstones 



Barren Beds. and Shales. 



Flat 

 Strata. 



Fig. 323. — Map of the northern part of the Richmond area of the Triassic system, show- 

 ing the effect of faults on the outcrops of the several members of the series, and on 

 their relations to associated formations. (Shaler and Woodworth, U. S. Geol. Surv.) 



sufficiently long to reduce the area where they occur essentially to 

 base-level. The time involved must have been very great, for the 

 hard trap, as well as the softer sedimentary formations, was brought 



