(46) 



defined by him. Professor Cook from 1863 until his death 

 in 18S9 published annual reports as state geologist of New 

 Jersey and early subdivided the Cretaceous into the three 

 marl beds, the clay-marls and the plastic clays. The Cre- 

 taceous was extensively summarized and described by him in 

 the Geology of New Jersey, published in 1868, the clay-marls 

 being divided into a lower member of clay containing green- 

 sand and an upper member consisting of laminated sands 

 The thickness of the formation was placed at 277 feet, 170 

 feet for the upper, and 107 feet for the lower member, and 

 over a dozen localities were enumerated where the clay-marls 

 were dug as fertilizer. In 1891 Professor William Bullock 

 Clark commenced a study of the coastal series of New Jersey 

 which has been in progress ever since. Three official reports 

 have been published : a Preliminary Report,* a Report of 

 Progress,! and a Final Report ; | besides numerous other 

 papers from which many of the following facts in regard to 

 the areal distribution and thickness of the Matawan forma- 

 tion have been quoted. 



The name Clay-marls was proposed by Cook ; his char- 

 acterization was incomplete, however, and was confined almost 

 entirely to their development in northern New Jersey. This 

 name does not adequately designate the formation lithologi- 

 cally and has been superseded by the name Matawan 

 formation of Clark. § The Matawan is separated from 

 the Piedmont plateau by a tract of Raritan, or Lower Cre- 

 taceous, which is some ten to fifteen miles wide. The Mata- 

 wan is nine to twelve miles wide in Monmouth county, 

 becoming narrower to the southward, being reduced to about 

 six miles in width in southern New Jersey ; on the western 

 shore of the Delaware river in Delaware it is further reduced 

 to from two to three miles ; further south on the eastern 

 shore of Maryland it broadens, being about five miles wide 



*Ann. Rep. State Geol. N.J. 1892: 167-245. 1893. (Clay-marls, pp. 

 186-190.) 



tAnn. Rep. State Geol. N. J. 1893: 329-355. 1894. 

 t Ann. Rep. State Geol. N. J. 1897 : 161-210. 1898. 

 2 Jour. Geol. 2 : 163. 1894. 



