NEWARK ROCKS OF ROCKLAND COUNTY, N. Y. 49 



well borings near the water front are reported to have penetrated 

 the shales and entered crystalline rocks beneath. On the Dela- 

 ware and in Pennsylvania the Newark beds are known to rest on 

 the older rocks along the southeastern border. There is no reason 

 for suspecting that the eastern border is marked by faults. On 

 the contrary, all the evidence, meager as it is, points to the above 

 conclusion, that here they rest normally though unconformably, 

 on the older rocks. 



Conditions of formation. In another paper 1 I have considered 

 at some length the conditions under which these beds were formed. 

 The following gives the main facts of that discussion. 



The Newark beds of New York and New Jersey were deposited 

 in a shallow estuary, whose shores were laid bare for consider- 

 able distances by the retreating tide and in which varying cur- 

 rents deposited coarse and fine materials. Shallow water con- 

 ditions prevailed throughout the entire period of deposition. 

 Since the beds are several thousand feet thick, subsidence of the 

 estuary bottom took place simultaneously with the sedimentation. 

 The material was derived from the adjoining land areas on the 

 northwest and southeast. The comparative absence of crystalline 

 pebbles and the great abundance of crystalline residuary material 

 indicate that at the beginning of Newark time the rocks were 

 very deeply disintegrated. The thickness of this mantle is best 

 explained by supposing that the adjoining land was at or near 

 base level. But the presence of pebbles several inches in diameter 

 in the Newark beds indicates that during the period of deposition 

 the streams had a velocity not consistent with streams on a pene- 

 plain. It is believed, therefore, that an elevation of the neighbor- 

 ing land areas marked the beginning of Newark time. The sub- 

 sidence of the estuary bottom was probably complementary to 

 the elevation of the adjoining areas. Stronger currents prevailed 

 in the northern part of the estuary, so that the average of deposits 

 was coarser there than farther south. 



Along the northwestern shore the waves beat on cliffs of lime- 

 stone and quartzite more than on those of gneiss or granite, and 



lAnnual report of the state geologist of New Jersey for 1897. p. 139-48. 



