94 BULLETIN OF THE 
of Cretaceous age. It still seems possible that the fragmeuts containing 
fossils may be in their nature exotic, as are the fossiliferons materials in 
the beds at Gay Head. It is to be noted, however, that the greenish 
gray sand in the section containing the fossils differs considerably in its 
general aspect from the beds at Gay Head. Moreover, there appears to 
be an absence of lignites in this portion of the Vineyard series. 
The prevailing northwest dips of this section are in contrast to the 
attitude of the Gay Head series. I have carefully examined the bedding 
with reference to the theory that the dislocation is due to glacial thrust. 
I find it impossible to accept this view, for the following reasons. In the 
first place, the dips are everywhere tolerably uniform, except within a 
foot or so of the glaciated surface. In this uppermost part of the section 
the thrusting and dragging action of the ice is distinctly exhibited in the 
somewhat sharp flexure of the beds, as well as the considerable contor- 
tion which they present. It seems to me impossible to believe that a 
steadfast dip such as is shown by these beds could have been produced 
by the thrust of a glacial sheet. Ifthe dislocation were due to the direct 
forward movement of the ice, we should have to explain these dips by the 
supposition either that the beds originally horizontal were thrown into 
an arched form, and that we have here the northwest side of the anti- 
clinal, or that the beds were completely overturned in order to produce 
the existing dips. There is no trace of such an arch exhibited in the 
section. Indeed, the presence of such a fold is contra-indicated by the 
fact that the dips increase to the southward, and the hypothesis of a 
complete overturn finds no support whatever in the facts. Last of all, 
we observe that the surface of this district apparently retains its pre- 
glacial topography. A system of stream valleys is traceable over all the 
section where the Vineyard series of deposits rise above the sea level. 
The persistence of a pre-glacial topography, manifest even in the details 
of the surface, —a topography on which the drift materials are simply 
imposed, — is overwhelmingly against the supposition that the disloca- 
tions are in any measure due to the action of the ice-sheet. 
In a memoir on the Geology of Martha’s Vineyard, prepared for 
the Annual Report of the Director of the U. S. Geological Survey for 
1885-86, I have endeavored to show that the deposits at Gay Head, 
probably of Miocene or early Pliocene age, were formed in a delta at 
a time when the level of the shore was perhaps not more than 200 
feet below its present position. If the evidence from the fossils and 
the physical condition of these Cretaceous deposits is to be trusted, it 
indicates that in a much earlier time the shore on this part of the 
