THE TRIASSIC PERIOD. 7 



amount of feldspar, derived, no doubt, from the bordering areas of 

 metamorphic rocks. Fourth, both the sandstone and shale contain 

 considerable quantities of mica. 



In general, it may be said that the crystalline schists adjacent 

 were the principal source of the materials entering into the clastic 

 part of this series, but where it borders formations of other sorts, they 

 made their appropriate contributions. The limestone and the coaJ 

 of the series are local, and of slight thickness. 



Fig. 310. 



•f + + + + + +++ ■ 



Fig. 311. 

 Fig, 310 shows limestone conglomerate forming along shore, where waves beat 

 against a limestone cliff (Im), while Fig. 311 shows how faulting might conceal the 

 limestone which furnished the material for the conglomerate. Subsequent erosion 

 might expose the limestone conglomerate, without exposing the formation from 

 which it was made. 



Conditions of origin. — The character of the Newark formations and 

 their fossils, mainly land plants, footprints of reptiles, and fresh- or 

 brackish- water fishes, point to the conclusion that they are of continental 

 rather than of marine origin, though the precise manner in which they 

 were laid down is not known. That deformation of the surface of 

 Appalachia, which had been reduced nearly to planeness by erosion, 

 gave rise to elongated depressions in which the Triassic sediments were 



