GENERAL CHARACTER OF THE CRETACEOUS DEPOSITS. 343 



clays are the most conspicuous, although these deposits, as well as the 

 calcareous beds of more local development, contain glauconite in greater 

 or less amounts at nearly every horizon. As the materials, however, 

 differ considerably from one another in general aspect in the several for- 

 mations, the deposits of each horizon will first be briefly characterized 

 and then contrasted with the other members of the series. 



The deposits of the Matawan formation consist chiefly of thick-bedded 

 sands and cLnys in which the glauconite is for the most part developed 

 in seams and pockets, in this particular standing in marked contrast to 

 all the succeeding members of the upper Cretaceous, where the glaucon- 

 ite is widely, although at times sparingly, disseminated. The clays of 

 the Matawan formation are also much more homogeneous than in any 

 of the succeeding formations, while the unctuous character of the mate- 

 rials is unknown at later horizons. The rapid alternation of finely lami- 

 nated black clays with white gritty sands, especially well shown in 

 Monmouth county, is very different from anything observed elsewhere 

 in the Upper Cretaceous series. 



The deposits of the Monmouth formation consist of a great body of 

 greensand marls and argillaceous beds, more or less highly glauconitic, 

 and situated, where most tj^pically developed, between two horizons of 

 red sands, the latter commonly thick bedded and often indurated in 

 places. The materials of the Monmouth formation are quite distinct 

 from those of the underlying Matawan in their general aspect. The 

 sandy and more glauconitic marls of the Matawan, particularly in the 

 southern part of New Jersey, show some points of resemblance to the 

 more marly members of the Monmouth, but in general the differences 

 are very marked. On the other hand, a comparison of the materials of 

 the Monmouth with those of the overlying formations shows again a 

 clearly defined difference in the character of the beds. The greensand 

 marls of the Monmouth formation are in general less highly glauconitic 

 than the deposits of the higher formations, and can be readily separated 

 both on account of their color and the general composition of the beds. 

 The red sands are quite unknown at later horizons except in certain 

 marginal phases of the Rancocas formation, where even here the weath- 

 ered glauconite generally retains enough of its character to reveal the 

 true nature of the strata. 



The deposits of the Rancocas formation consist for the most part either 

 of highly glauconitic greensands or of calcareous beds in which the 

 glauconite is widely disseminated. The thick bedded greensands, which 

 may at times become chocolate colored by the admixture of argillaceous 

 materials, can be usually readily distinguished from the glauconitic 

 members of the lower formations, although materials more or less closely 



