48 H. B. KUMMEL 



The same thing is true of the Sand Brook sheet, the thick- 

 ness of which is apparently not less than 425 feet. 



Too little is known of the relations of the Sourland Moun- 

 tain, Pennington Mountain, Bald Pate, and Rocky Hill traps to 

 the inclosing shales to venture estimates of their thickness. 



Deposition. — Most geologists hold the view that the Newark 

 beds are estuarine deposits. Some, however, prefer to consider 

 them lacustrine, believing that the scarcity of fossil remains ren- 

 ders improbable the supposition that the sea had free access to 

 the basin. The fauna and flora preserved for us are meager, 

 and do not settle the question decisively, the forms being 

 such as might have existed either in an estuary or a salt lake. 

 On the other hand, the distribution of the material implies well- 

 marked currents such as the tides would produce in an estuary. 

 For myself I prefer to believe that at the beginning of Newark 

 time a broad, shallow estuary extended across the northern part 

 of what is now New Jersey and into New York state. Whether 

 the estuary was wider than the present area of the beds is impos- 

 sible to say. Subsequent erosion has diminished their areal 

 extent, whereas faulting, particularly in the western part of 

 New Jersey, has increased it. Which of these factors has been 

 the more effective is uncertain. Probably along the Delaware 

 River section the gain by faulting has exceeded the loss in 

 width by erosion. In the north this may not be the case. 



The estuary was bordered on the northwest and southeast by 

 areas of granite, gneiss, and schist, probably pre-Cambrian in 

 age, with narrow belts of Paleozoic quartzite, limestone, and 

 shale. The latter rocks formed in part the floor of the estuary, 

 the foundation on which the Newark deposits were made. This 

 is shown by the "island" of limestone and quartzite brought to 

 the surface in Pennsylvania by the Flemington fault. For long 

 periods previous to the formation of the estuary and the deposi- 

 tion of the Newark shales, the older rocks on which they now 

 rest had been a land area and were deeply eroded. The proof 

 of this is found in the absence from this region of all the later 

 members of the Paleozoic series. 



