THE GREENSANDS OF NEW JERSEY. lyj 



more constant, although there were times when it became greatly 

 reduced in amount on account of the advent of large amounts of 

 sand and mud from the adjacent coasts. 



From the known conditions requisite for the production of 

 glauconite upon the bed of existing seas, and the possible 

 position of the coast line in Cretaceous time, it seems likely 

 that the greensands now outcropping at the surface were laid 

 down from fifteen to thirty miles off the coast. Frequent 

 changes of level no doubt took place, but the variations in the 

 character of the deposits were probably quite as much due to 

 fluctuations in the currents as to pronounced changes in the posi- 

 tion of the coast line. 



The marked thickening of the Matawan formation seaward, 

 as shown by the well-boring at Asbury Park, is of interest as 

 indicating the more permanent character of the deposition out- 

 side the area of mechanical disturbance such as characterized the 

 shallower portions of the Matawan sea floor. 



The alterations which have taken place in the exposed por- 

 tions of the deposits are oftentimes widespread, and in the case 

 of the indurated layers at the top of the Redbank formation 

 have determined to a large extent the topography of the green- 

 sand district. 



Many interesting problems are presented for further study, 



but it is hoped that this paper may contribute somewhat to a 



clearer understanding of greensand deposits in general, and those 



of the New Jersey area in particular. 



William Bullock Clark. 

 Geological Department 

 Johns Hopkins University. 



