THE GREENS A NDS OF NE W J ERSE Y. 167 



centage of soluble phosphates in the Manasquan marl has long 

 given it a high reputation as a fertilizer. 



The thickness of the strata has been estimated at 65 feet. 



Shark River formation (Upper portion of the Upper Marl 

 Bed). — The term Shark River Marl was earlier employed by 

 the writer to embrace the "blue marl" of the Upper Marl Bed, 

 which has been generally referred in recent years to the Eocene, 

 although the beds are conformable with the underlying strata 

 concerning whose Cretaceous age there is apparent unanimity of 

 opinion. 



The Shark River formation is a characteristic greensand with 

 a slight admixture of argillaceous materials, while a hardened 

 and stony layer is found directly at the top. The fossils are 

 numerous, but cannot be readily compared with those from the 

 Eocene areas to the southward. The strata of the Shark River 

 formation have not been found at any point to exceed 12 feet in 

 thickness. 



The Shark River formation closes the series of greensand 

 deposits. It is unconformably overlain by strata of a very dif- 

 ferent character which show evidence of marked mechanical dis- 

 turbances and rapid deposition. 



Throughout the entire sequence of deposits just described, 

 the presence of greensand has been the most distinguishing 

 feature. Its origin is therefore a matter of great importance to 

 the understanding of the several formations, and will be briefly 

 discussed. 



ORIGIN OF GREENSAND. 



Greensand has been found in greater or less amounts at 

 nearly every geological horizon, from the Cambrian down to the 

 present time. It is not an original deposit of clastic origin, but 

 secondary in character. An examination into the conditions of 

 production which surround those deposits forming upon the floor 

 of existing seas will afford an explanation of the strata of past 

 geological time. 



Great light has been thrown upon this subject as a result of 

 he deep-sea dredgings which have been made in recent years 



