i8o CRETACEOUS PALEONTOLOGY. 



obtained at the various localities during this period. In the 

 south, at least east of the Mississippi River, all the marine Upper 

 Cretaceous faunas seem to be of Ripleyian age, although it is, of 

 course, possible that a thorough investigation of the faunas of 

 that region will necessitate some modification of this interpreta- 

 tion. 



The Ripleyian fauna as seen in New Jersey is a complex 

 assemblage of organisms with two or more distinct facies, which 

 were doubtless associated with different environmental conditions,, 

 such as depth of water, chai'acter of the sea bottom, etc. As has 

 been pointed out, twO' distinct facies of the fauna have here been, 

 distinctly reco'gnized, one of which, the CuciUlaea fauna, as it has 

 been called in the preceding pages, is characteristic of the more 

 glauconitic beds, the Merchantville, Marshalltown, Navesink and 

 Tinton. The second faunal facies, characterized by Lucina 

 cretacea or its associates, occurs in the clays and sandy clays of 

 the Cliffwood, Woodbury, Wenonah and Red Bank formations. 

 In the existing seas the areas where glauconitic sands are being- 

 formed under the most favorable conditions are some distance off' 

 shore at depths beyond the action of waves and currents, and at 

 sufficient distance from the mouths of rivers to be comparatively 

 free from terrigenous sediments.^ The sands and clays, on the 

 other hand, are deposited nearer shore. The faunas associated 

 with the two types oi sediments in the New Jersey Cretaceous 

 beds were doubtless characteristic of the deeper and the shallower 

 waters. The existence, therefore, of these two alternating faunal 

 facies with the particular types of sediments with which they are- 

 associated, within the pre;gent belt of outcrop of the Cretaceous 

 in New Jersey, necessitates the assumption that the Cretaceous 

 shore across the present area of New Jersey was subjected to a. 

 series of oscillations, being alternately elevated and depressed. 

 During the periods of depression the deeper waters, with the 

 accompanying glauconitic sediments and the CticiMaca fauna, 

 gradually crept to the northwest and occupied a belt which had 

 formerly been inhabited by the shallower water fauna, and where 



' For a discussion of the "Origin of Greensand" see Geol. Surv. N. J., Ann_ 

 Rep. of State Geol. for 1892, pp. 218-239. 



