348 W. B. CLARK — UPPER CRETACEOUS FORMATIONS OP NEW JERSEY. 



Maryland, while in the intervening district of central and southern New 

 Jersey the sedimentation was probably of a much finer character, as 

 shown by the chocolate colored marls of that area, unless, perchance, 

 subsequent erosion had caused the removal of all the sandy sediments. 



The succeeding Rancocas epoch was a time of slow accumulation of 

 continental materials throughout the northern Atlantic Coastal plain, so 

 that the production of glauconite went on unhindered. During the later 

 portion of the epoch, however, there must have been a great profusion of 

 bryozoan life, since the deposits show a remarkably large proportion of 

 calcareous materials, largely made up from the shells of these organisms, 

 the percentage of carbonate of lime at times exceeding 80 per cent of the 

 whole. The conditions most favorable for the production of these de- 

 posits were found in central and southern New Jersey, particularly in 

 the region of Salem county. 



The Manasquan epoch was characterized throughout by conditions 

 favorable to the formation of highly glauconitic deposits, but land- 

 derived materials in considerable amounts reached the area just at the 

 opening of the epoch as well as in a less pronounced degree toward its 

 close. 



The Shark River epoch succeeded the Manasquan without evidence of 

 any marked change in the physical features of the district, conditions 

 favorable to the production of glauconite still continuing, so that if the 

 Shark River formation is considered of Eocene age, a subject which will 

 be later discussed, then we have no physical break between the Creta- 

 ceous and Eocene at this point. 



At the close of the Shark River epoch the conditions favorable to the 

 formation of greensand ceased throughout that portion of New Jersey 

 which we have been hitherto considering. To the south, in Delaware 

 and Maryland, the Eocene period was one of greensand production, and 

 the representative of those deposits may today exist far to the southward 

 in New Jersey, buried beneath Miocene strata, but its presence has not 

 as yet been definitely shown in the well records. 



PROBABLE CONTINENTAL RELATIONS AS REVEALED BY THE DEPOSITS. 



The deposits of the upper Cretaceous afford evidence either that the 

 land of the period was supplying little sediment to the sea or that these 

 Cretaceous materials were laid down so far from the shoreline that but 

 a relatively small amount could reach the area. A brief history of events 

 just prior to the opening of the upper Cretaceous may aid in the inter- 

 pretation of the continental relations during that period. 



The Lower Cretaceous period is characterized by deposits which give 

 evidence of a gradual submergence of the eastern border of the conti- 



