Appalachian Geosyncline. 101 



up with respect to the conglomerates and bringing the pre- 

 Cambrian against them. In a few places, however, the gneisses 

 had begun to be exposed toward the close of Newark time as 

 shown by the gneissic conglomerates in certain of the higher 

 beds of the Newark. 



The conglomerates have been attributed by various investi- 

 gators to wave origin, or even to glacial, but J. Yolney Lewis 

 regards the Newark as essentially a fluviatile formation,* and 

 J. D. Dana came to somewhat the same conclusion. f The 

 present writer holds the Newark formations to be fluviatile, 

 but differs from the last two authors cited in believing that the 

 sediments of the New Jersey area came largely from the east, 

 from regions now submerged beneath the sea. Considerable 

 material was of course supplied from the northwestern fault 

 wall as shown by the quartzite conglomerates, but the gneisses 

 and granites on that side were not then exposed to erosion and 

 could not have been the source of the feldspathic and mus- 

 covitic debris which makes up much of the Newark rocks. 



Where the Triassic floor is exposed on the northwestern 

 side of the basin at several localities between the Hudson and 

 Susquehanna rivers it is seen to consist of Cambro-Ordovician 

 rocks. After many thousands of feet of deposition the north- 

 western wall was still dominantly mantled by Cambro-Ordovi- 

 cian limestone. The uplift on the northwest side of the margin 

 during sedimentation was therefore moderate, the downthrow 

 on the southeast side of this margin was very great. Distribu- 

 tive or step-faulting probably existed, rather than a single 

 simple fault, so that farther northwest the crust may have been 

 more elevated than against the immediate margin of the 

 Triassic and may account for some of the overlapping relations 

 observed in Pennsylvania. 



The quartzite conglomerates seem to be clearly of fluviatile 

 origin without indications of contributing glaciers. Wherry 

 has recently favored the view that glaciers were the ultimate 

 source of these bowlders,:}; but the cobbles could be moved 

 along the bottoms of rivers such as those which now drain the 

 Appalachians, and their counterparts could be found in those 

 south as well as north of the recent glacial limit. They are 

 dominantly of one character in any one exposure. The 

 quartzite cobbles are well waterworn, but such as are sub- 

 angular show commonly that the subangularity is the result of 

 breakage and not of glacial wear. In size the bowlders aver- 



* The Origin and Relations of the Newark Rocks, Ann. Report U. S. Geol. 

 Surv. for 1906, pp. 99-129, 1907. 



+ Manual of Geology. 743-745, 1895. 



% E. T. "Wherry : North border relations of the Triassic in Pennsylvania, 

 Proc. Acad. Nat. Sci. Philad., pp. 114-125, 1913. 



