488 THE TRIASSIC PERIOD 



is not easily determined. In the Richmond area of Virginia, it is 

 estimated at something more than 3,000 feet; in New England, at 

 7,000 to 10,000 feet; and in New Jersey even more. 



CORNWALLIS HILL 



TUCKAHOE CREEK 



Yi 



Fig. 415. Structure of the Newark series on the James River, Richmond area, 

 Va. AA, minor flexures; ff, faults. Structure of the deeper parts hypothetical. 

 The heavy black band represents coal. (Shaler and Woodworth, U. S. Geol. Surv.) 



Correlation. The stratigraphic relations of the Newark series in 

 the United States would not determine its age. It lies unconfor- 

 mably on rock which is mainly pre-Cambrian, and is overlain un- 

 conformably by Comanchean (Lower Cretaceous) beds. About 

 the Bay of Fundy, however, the rocks are unconformable on the 

 early Permian. The physical relations of the Newark series there- 

 fore show that it is post-early-Permian, and pre-Comanchean. 

 In referring the series to the Triassic, the chief reliance is on the 

 fossils, and on the same basis it is believed to represent only the 

 later part of the period. 



The Western Triassic 



The western interior. 1 The interior area of sedimentation, 

 chiefly between the looth and ii3th meridians, had its southern 

 limit* so far as now known, near the southern boundary of the 

 United States, while at the north it extended into Canada. This 

 area is believed to have been cut off from the Gulf by land in eastern 

 Texas. Into this interior area of sedimentation, detritus was borne 

 from the surrounding lands. The conditions of sedimentation were 

 much as in the Permian period. The structure of some of the sand- 

 stone is such as to suggest an eolian origin. 



The deposits of the period are largely concealed by later beds, 

 but they are exposed at various points where the strata have been 

 warped, and the overlying beds removed by erosion. The most 

 easterly outcrops are in Texas, Oklahoma, and South Dakota, and 



1 There is some doubt about the age of some of the beds formerly referred to 

 this system. The tendency of later study has been to refer more and more of 

 them to the Permian. 



