14 



CAPE COD GEOLOGY 



The flora of the Cretaceous beds of Marthas Vineyard was still later diag- 

 nosed by Berry, 1 who referred the leaf-bearing beds to the Magothy formation 

 in the following terms: 



The upper Cretaceous flora of Marthas Vineyard is extensive, comprising 117 recorded 

 species and coming from three localities (Chappaquiddick, Nashaquitsa, and Gay Head), 

 the bulk of the material coming from Gay Head. This flora has been elaborated by David 

 White and Arthur Hollick. The latter author considered it equivalent to the Raritan forma- 

 tion of New Jersey, but it is obviously younger and equivalent to the Magothy formation. 

 Fifteen of the recorded species are confined to Marthas Vineyard. Of those having an outside 

 distribution, 67 are not found in the Raritan, and of the 35 forms that occur in the Raritan, 

 29 are also common to the overlying Magothy, leaving six peculiar forms, and these are all 

 vague or unique specimens (Carpolithus, Williamsonia, Tricarpellites, Tricaly cites). Nearly 

 all of the Marthas Vineyard plants that occur outside of that area are common to the Magothy 

 of New Jersey or Maryland or to post-Raritan formations elsewhere. Thus 44 species occur 

 in the Magothy and 20 are peculiar to Marthas Vineyard and known Magothy, so that I have 

 no hesitation in correlating the leaf-bearing Cretaceous of Marthas Vineyard with the 

 Magothy formation. 



The classification of the Cretaceous beds of the Atlantic coastal plain in 

 areas where they have been undisturbed by glacial action has been fairly well 

 determined, and the geologic relations of the plant-bearing beds in the New 

 England Islands can be stated in terms of the formations discriminated in New 

 Jersey and Maryland. In the gulf region the Lower Cretaceous or Comanche 

 series is represented by marine deposits, but on the Atlantic coast it is represented 

 by nonmarine deposits, the northeastern beds of which belong to somewhat later 

 stages of deposition. Thus the Lower Cretaceous deposits of Maryland, com- 

 prising the Patuxent, Arundel, and Patapsco formations, here named in ascending 

 order, disappear northward through the gradual transgression of the Arundel 

 and the Patuxent by the unconformably overlying Patapsco formation, and this 

 in turn disappears beneath the Magothy formation, which locally lies at the base 

 of the Upper Cretaceous series in the New England Islands. 



The most continuous exposure of the Upper Cretaceous series in the area 

 here considered is that seen in the cliffs at Gay Head (see plate 14) ; but even there, 

 owing to the complex of overturned folds and thrust faults, neither the number, 

 the exact order, nor the thickness of the beds can be exactly determined except 

 for a small part of the section. The following section may be seen in the cliffs at 

 Gay Head, in front of the lighthouse : 



Section of Upper Cretaceous Beds Exposed at Gay Head 



Quartz-bearing kaolinite at top, bleached white, alternating with a bed of white clay 

 about four feet thick and merging into cross-bedded quartz gravel below. The cast of a pele- 



1 Jour. Geology, 23, pp. 608-618, 1915. 



