INTRODUCTION. 15 



clays on the south shore of Raritan Bay, making- the name Raritan 

 nearly the equivalent of Cook's "plastic clay" series.^ 



Knapp's study of the Cretaceous was carried on in connection 

 with work on the Pleistocene foiinations. The progress and 

 results of that work are briefly given in the following paragraphs, 

 which have been prepared by him. 



BY G. N. KNAPP. 



Early in the work on the Pleistocene formations it was found 

 necessary to make a careful study of and to map the subjacent 

 Cretaceous beds in order to differentiate some of them from the 

 Pleistocene sands, which they closely resembled. Beginning in 

 April, 1894, the Cretaceous formations were, therefore, mapped 

 from Crosswicks Creek southwest to Rancocas Creek. In 1895 

 the work was continued southwest from' Rancocas Creek to 

 Salem, and in 1896 the mapping was carried northeast from 

 Crosswicks Creek across Monmouth County to Asbury Park and 

 Atlantic Highlands. In 1900-1903 the detailed mapping was 

 revised, and the lines delimiting the Cretaceous formations were 

 more accurately fixed. 



In 1894, when this work was begun, the only comprehensive 

 description of the New Jersey Cretaceous was that by Cook,^ 

 and the only geological maps available were those accompanying 

 the 1868 Report (scale 2 miles per inch) and the various State 

 Geological maps on the scale of 5 miles per inch. Dr. Clark had 

 begun work on the Cretaceous in New Jersey in 1891, and the 

 State Geologist's Report for 1892 contained a report of progress 

 of his work and a preliminary map of the Cretaceous in Mon- 

 mouith County. A second report of progress by Dr. Clark was 

 contained in the Annual Report for 1893, which was issued dur- 

 ing the summer of 1894, after the writer had commenced his 

 mapping in Burlington County. The classification then proposed 

 by Dr. Clark was not entirely in accord with the writer's observa- 

 tions in the region southwest of that in which most of Clark's 



' Geol. Surv. N. J., Ann. Rep. of the State Geol. for 1892, p. 181 ; Ibid, for 



1893, P- 33S. 



' Geology of New Jersey, 1868, and Annual Report for 1886. 



