777^ GREENSANDS OF NEW JERSEY. 1 71 



the complete oxidation of the glauconite was accomplished. 

 Toward the close of the Redbank epoch finer sediments prevailed, 

 and there is every evidence that land-derived materials found 

 ingress to the area of deposition in gradually lessening amounts. 



The succeeding Rancocas epoch was a time of slow accumu- 

 lation of continental materials so that the production of glau- 

 conite went on unhindered. During the latter portion of the 

 epoch, however, there must have been a great profusion of animal 

 life, for the deposits show a marked admixture of carbonate of 

 lime, while in many instances the shells are still in an excellent 

 state of preservation. The formation of glauconite was not 

 interrupted, although its relative proportion is at times much 

 diminished by the great amount of carbonate of lime which may 

 in some instances reach eighty per cent, of the whole. 



The Manasquan epoch was characterized throughout by the 

 constant formation of greensand beds, although land-derived 

 materials in considerable amounts reached the area of deposition 

 during the early portion of the period. 



No very marked changes apparently affected the region 

 toward or at the close of the Cretaceous, but the same conditions 

 persisted on into the Eocene, as shown in the Shark River forma- 

 tion, during which period similar deposits with very different types 

 of animal remains were accumulated. At the close of the Shark 

 River epoch the conditions favorable for the formation of green- 

 sand ceased, not to be again revived during the period of forma- 

 tion of the coastal deposits in New Jersey. 



The succeeding epochs gave proof of much shallower waters, 

 while the ancient Cretaceous-Eocene sea floor frequently stood 

 above sea level and along its landward portions constantly lost 

 as the result of erosion. As the land rose higher and higher in 

 late geological history further inroads were made until the deeper 

 portions of the ancient sea bottom were exposed by the forces of 

 denudation. 



SOURCE OF THE MATERIALS. 



The source of the materials which constitute the several 

 formations of the coastal region of New Jersey has not been 



