350 W. B. CLARK — UPPER CRETACEOUS FORMATIONS OF NEW JERSEY. 



duced, so far as observed, no marked structural change in the Upper 

 Cretaceous strata, although the beds have been gradually depressed sea- 

 ward, so that each succeeding group of deposits has come to lie at a 

 slightly lower angle. Slight deformation, both along the strike and dip, 

 has been observed, the explanation for which is sought in movements 

 which have taken place subsequent to the formation of the strata, al- 

 though no doubt in part explained by the uneven surface upon which 

 the deposits themselves were laid. 



Chemical changes of considerable moment have taken place in the 

 beds, often obscuring the original character of the strata. The most con- 

 spicuous of these alterations has been the weathering of the glauconite? 

 which has changed the deposits from green or grayish green to brown or 

 reddish brown in color. This is especially marked in the more porous 

 strata or along the thinned out margins of all the formations. At times the 

 glauconite grains have been entirely destroyed, while at other times the 

 surface only has been weathered, and when crushed the greenish interior 

 is shown. At times induration takes place, producing either shelly layers 

 or thick beds of ironstone. The ironstone deposits have very materially 

 affected the topography of the northern Atlantic Coastal plain, these hard 

 beds protecting the underlying formations from removal. The escarp- 

 ment in northern New. Jersey owes its prominence very largely to the 

 protection thus afforded. 



The other deposits have also suffered greater or less change in their 

 surface exposures, the dark clays especially becoming lighter colored as 

 the carbonaceous materials contained in them have been changed or 

 removed by the percolating waters. 



Interpretation of the faunal Record. 

 correlation of the formations within the province. 



The several formations of the upper Cretaceous of the northern Atlantic 

 Coastal plain are highly fossiliferous throughout- the area of their occur- 

 rence, so that, with few exceptions, the paleontological evidence is ade- 

 quate for the correlation of the strata from their northern to their southern 

 limits (plate 48). 



The Matawan formation is less highly fossiliferous than the other 

 divisions of the upper Cretaceous. At certain localities, however, the 

 species represented are very numerous, but the fossiliferous bands are 

 less persistent and the individuals seldom so abundant as in the suc- 

 ceeding formation. The several species of ammonites referred to in the 

 list of fossils are especially characteristic of the Matawan formation, 

 Ammonites delawarensis and several of the forms of Scaphites not having 



