CAPE COD GEOLOGY 



13 



Cretaceous System 

 (See Plate 4) 



The beds of lignitic clay and the associated beds of white and mottled clay 

 on Marthas Vineyard were assigned to the Cretaceous system in 1890 by David 

 White, who identified certain fossil plants found in them at Gay Head, in the 

 western part of that island. He states that ' 'the flora indicated an age certainly 

 Cretaceous, and probably middle Cretaceous, for the terrane in which it was 

 deposited." * 



Just before White identified these plants Shaler 2 announced the discovery, 

 in the eastern part of Marthas Vineyard, of angular fragments of a coarse sand- 

 stone, which were at many places embedded in the morainal deposits and which 

 had apparently not been transported more than a few hundred feet. Moreover, 

 near Indian Hill blocks of sandstone were associated with tilted beds of uncon- 

 solidated sand that were regarded by Shaler as of the same age. In his opinion 

 the Cretaceous beds were limited to a small area that was surrounded by beds 

 of Tertiary clay. Fossils found in the sandstone indicated that the beds con- 

 taining them were not later than middle Cretaceous. 



The fossil plants identified by White had before been regarded as possibly 

 Tertiary in age, and in view of the restriction of the recognizable Tertiary beds 

 (Miocene and Pliocene) at Gay Head to a few feet of greensand and other sand, 

 it became evident in 1889 that the beds of white sand and the associated beds of 

 clay, of various colors, as well as the beds of lignite at Gay Head and elsewhere 

 on Marthas Vineyard, are members of the series of Cretaceous deposits exposed 

 at Perth Amboy and other places on the Atlantic coastal plain. 



Dr. Arthur Hollick, continuing the investigation of the leaf-bearing clay beds 



begun by White, discovered an extension of these beds on Nonamesset Island 3 



and correlated these leaf-bearing beds with beds found farther west, on Long 



Island and Staten Island. 4 As a result of later studies at Gay Head, Hollick 6 



writes : 



The stratigraphic relations of the various beds represented in this section are too uncertain 

 for definite conclusions on account of the tilting and distortion to which they have been sub- 

 jected; but inasmuch as 103 species of fossil plants, a large majority of them representing 

 well-known Cretaceous types, have been identified from this locality alone, the age of the beds 

 from which they came cannot be questioned. Both the Raritan and the Cliffwood (Magothy) 

 formations are represented in these species. 



1 Am. Jour. Sci., 3d ser., 39, pp. 93-101, pi. 2, 1890. Also Bull. Geol. Soc. Amer., 1, pp. 554-555, 1890. 



2 Bull. Mus. Comp. ZooL, 16, pp. 89-97, pis. 1, 2, 1889. 



3 Annals New York Aead. Sci., 13, pp. 387-418 (especially p. 394), 1901. 



4 The Cretaceous flora of southern New York and New England, U. S. Geol. Survey Mon. 50, pp. 

 27-28, 1906. 



6 Op. tit., p. 27. 



