CAPE COD GEOLOGY 



15 



cypod (cf. Pholadomya sp.) was found in a "quadrangular fold" in the kaolinite at the top 

 of the series. Probably marine in its upper part. 



White clay, in places stained deep red. Carbonized leaves of fossil plants found here 

 and there above the underlying bed of lignite. Same flora found in nodules at places where the 

 lignite has been forced over the clay, which has there become brownish from infiltrated iron 

 stains. Nonmarine. 



Lignitic clay and lignite at bottom ; exposed only in close anticlinal folds. Contains broken 

 trunks of trees and fragments of coniferous wood (B r achy phy Hum, Prepinus viticetensis 

 Jeffrey), 1 and amber. Nonmarine. 



The total thickness of the beds in this section probably does not exceed 150 

 feet. On the south side of the cliffs there is a long exposure of overturned beds of 

 clay, mottled white and red, having an apparent thickness of several hundred 

 feet, but the beds are undoubtedly repeated by folding. The narrow, squeezed 

 masses of white Cretaceous clay in closely folded beds at Ball's Point, on Block 

 Island, as well as most sections of the clay that are not associated with lignite 

 or that contain no fossil leaves afford little clue to their stratigraphic position. 



Marine fossils found near Indian Hill by Shaler in somewhat drifted blocks 

 of sandstone, an indurated part of one of the Cretaceous beds, show that the 

 marine division of the Upper Cretaceous system probably occurs on Marthas 

 Vineyard. Shaler regarded these fossils as not later than middle Cretaceous. 

 They probably belong at a horizon above the lignitic beds at Gay Head. Several 

 members of the United States Geological Survey have collected Cretaceous in- 

 vertebrate fossils in drifted argillaceous boulders on Marthas Vineyard. Accord- 

 ing to L. W. Stephenson, most of the species are nearly identical with those found 

 in the poorly preserved material collected by Shaler. The wide distribution of 

 these boulders over the island indicates that marine upper Cretaceous beds once 

 covered this district, and extended inland northward and northwestward. 



Stephenson regards the deposit on Marthas Vineyard as of Matawan age 

 and states that if Exogyra ponderosa has been correctly identified among the 

 fossils from the island, the fauna certainly falls within the zone of Exogyra pon- 

 derosa in the Matawan. 2 



Tertiary System 



EOCENE AND OLIGOCENE SERIES 



The Tertiary system is divided into the Eocene, Oligocene, Miocene, and 

 Pliocene series, which are here named in ascending order. The Eocene and the 

 Oligocene series are not represented by any known deposits that stand above 



1 Jeffrey, E. C, Annals of botany, 20, No. 80, pp. 383-394, pi. 28, 1906. Also Proe. Boston Soc. Nat. 

 Hist., 34, pp. 333-338, pi. 33, 1910. 



2 Report on collections of Upper Cretaceous invertebrate fossils from Marthas Vineyard, Mass. 



