THE TRIASSIC PERIOD 681 



great body of the Newark series, and both possess distinctive 

 characteristics. Their prevalent color is red, though there are 

 shales which are black, and sandstones which are gray. Except 

 locally, the series is poor in fossils. Some of the sandstone is arkose, 

 that is, contains a considerable amount of feldspar, and both sand- 

 stone and shale contain much mica. Both these constituents 

 abound in the metamorphic rocks from which the Newark sediments 

 were chiefly derived. 



Conditions of origin. The character of the Newark formations 

 and their fossils, mainly land plants, footprints of reptiles, and 

 fresh- or brackish-water fishes, indicate that they are of continental 

 rather than 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 deposited, seems certain. The depressions may have been 

 due to warping or to faulting, or partly to the one and partly to the 

 other (Figs. 465 and 466), and their development may have pro- 

 gressed as deposition went on. Some of them may have been broad 

 river valleys, which, in the general uneasiness which marked the 

 close of the Paleozoic era, became sites of deposition. However 

 formed, these depressions in the surface of the present Piedmont 

 region became the sites of lakes, bays, estuaries, dry basins, or 

 aggrading rivers. Lacustrine, estuarine, and fluviatile conditions 

 may have alternated from time to time in the various places where 

 sedimentation was in progress, and perhaps the sea gained access 

 to some of them from time to time. 



The considerable thickness of the sediments, taken in connection 

 with their decisive evidences of shallow- water or subaerial origin, 

 such as ripple-marks, sun-cracks, tracks of land animals, etc., 

 indicate either that inclined deposition prevailed, or that subsidence 

 of the areas of sedimentation accompanied the deposition. For 

 the adequate supply of the detrital material, it would seem that 

 the lands bordering the areas of deposition were raised, relatively, 

 as the troughs were filled. The general conditions of accumula- 

 tion may have been similar to those under which the Catskill for- 

 mation was deposited at an earlier time. 



