( 46) 
defined by him. Professor Cook from 1863 until his death 
in 1889 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,f 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cally and has been superseded by the name Matawan 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. 
+ Ann. Rep. State Geol. N. J. 1893: 329-355. 1894. 
tAnn. Rep. State Geol. N. J. 1897: 161-210, 1898. 
@Jour. Geol. 2: 163. 1894. 
