62 HOLLICK. 



Block Island with those of Martha's Vineyard to the east, and 

 Long Island, Staten Island and New Jersey to the west, and 

 shows them all to belong to the same Cretaceous horizon. 



Inasmuch as a prominent authority has published his opinion 

 that these clays are probably Jurassic in age, I perhaps can not 

 do better than to quote the words of Dr. Lester F. Ward, ex- 

 pressed after an examination of the material now in our posses- 

 sion from the region : 



''Those who are capable of supposing that such a flora as 

 this could have flourished in Jurassic time are certainly at lib- 

 erty to do so, and the geological world will doubtless duly ap- 

 preciate their couragej 



1" 



Stratigraphy. 



While engaged in collecting the material previously described 

 other matters of geologic interest were also incidentally noted. 



The lithologic characteristics of the basal (Cretaceous) clays 

 always served to distinguish them from the superficial (bowlder) 

 clays above. The latter are best represented on the south 

 shore, at Mohegan Bluffs (see plates V. and VI.) and consist of 

 contorted grayish sandy clay, in which gravel and occasioned 

 bowlders occur, but no organic remains. The Cretaceous clays 

 are exposed at Clay Head (see plate VII), Grace Point, and near 

 Black Rock Point and Old Harbor Point (see plate VIII.). They 

 are plastic and either black from the presence of lignite or else 

 pure white, yellow, red or bluish. Beds of white sand accom- 

 pany them at the two localities first mentioned. 



Observations on dip and strike are of but little stratigraphic 

 importance, on account of the contortion to which the beds 

 have been subjected by glacial action, and such observations as 

 were made merely tended to emphasize this fact, the dip in all 

 cases being toward the north, indicating that the strata had been 

 pushed southward in a series of overthrust folds by the advanc- 

 ing ice front. This was found to be uniformly the case with the 

 basal clays and largely so with the superficial ones, apparently 

 indicating that the latter as well as the former were laid down 

 previous to the advent of the ice. 



"^Science, IV (Nov. 20, 1896), 760. 



