140 w. h. hobbs — Former extent of the Newark system 



the now generally accepted view that the Newark boundaries are largely 

 along faults, for the lower beds of the system will occur nearest the 

 boundaries, due to the distribution of the displacement at their bound- 

 aries over a series of near-lying planes. 



GEOGRAPHIC CONDITIONS 



It is difficult to picture the conditions which prevailed in Newark 

 times, but the peculiar occurrence and distribution of this basal con- 

 glomerate may perhaps be accounted for if a broad land area of the 

 crystalline rocks were subjected to long-continued secular disintegration 

 in an arid climate, and subsequently depressed so as to admit the sea. 

 The deeply disintegrated rock masses would in the higher areas, where 

 the waves and tidal currents were effective, be washed free from the 

 finer material, and in consequence the pre-Newark land areas would be 

 mantled by a coarse arkose or conglomerate whose pebbles would have 

 only slightly rounded surfaces. The borders of the area and the island 

 peaks and ridges which projected above the water surface would there- 

 fore be surrounded by marginal zones of greater or less width made up 

 of conglomeratic material. In the deeper areas sandstone and shale 

 would be deposited. Where coarse pegmatites occurred giant conglom- 

 erates composed of large feldspars would locally be produced, as has 

 been the case, particularly in the New England areas. To these New 

 England areas the hypothesis fits particularly well, because of the dis- 

 tribution of the Mount Toby conglomerates, as described by Emerson,* 

 and the character of the Roaring Brook contact on the crystallines, as 

 described by Davis,f the irregular surface of the latter, and the local 

 derivation of the Newark material strongly favoring the view. 



Tt is not necessary to assume that the pre-Newark terrane was in all 

 parts depressed below sea level. The southern areas, with their coal 

 formations, indicate marshy areas with rank vegetation. If a geography 

 not unlike that of the great basin be pictured, with a change of climatic 

 conditions, the torrential streams from the steep walls and from the 

 island-like peaks and ridges may be appealed to for the sorting of the 

 sediments and the local transportation of the large rock fragments of 

 the conglomerate, as has been already suggested by Shaler and Wood- 

 worth. % 



The above review of the character and the distribution of the coarse 

 sediments has been somewhat fully considered, because they have been 



*0p. cit., p. 361. 



fOp. cit., pp. 19-23. 

 J Op. cit., pp. 404-406. 



