96 ABSTRACTS 



reason to place a limit to its advance. The presence of shells in a 

 recently abandoned moraine, as well as in the moraine now being 

 made, and in the ice itself, appears to prove a recent retreat of the 

 glacier, for these shells are of species novv living in the waters of the 

 fjord. They are found at a distance of five miles from the sea and at 

 an elevation of 586 feet above it, and at various levels below this. 

 The description of records left near the margin of this glacier is given, 

 with the idea of putting forward facts which will permit accurate 

 measurement of the change of ice front in the future. This seems all 

 the more desirable, since evidence is abundant that the glacier in this 

 part of Greenland is now retreating at a notable rate, and that it has 

 recently withdrawn from a considerable area. The evidence of this 

 is found in the presence of moraines at a distance of 100 or 200 feet 

 from the present margin of the glacier, and so recently abandoned 

 that no vegetation has begun to grow upon the soil. Moreover, 

 freshly scratched bedrock has been so recently uncovered by the glacier 

 that lichens have not beafun to arrow. 



Unconformities in Marthas Vineyard and Block Island. By J. B. 



WOODWORTH. 



Beginning below, plant-bearing beds of Cretaceous age appear in 

 both islands, without their base being exposed. On Marthas Vineyard 

 marine Cretaceous strata overlie the non-marine beds ; although the 

 contact has not been worked out, unconformity is inferred from the 

 occurrence of lignitic fragments in the overlying marine beds. Above 

 the Cretaceous at Gay Head, and on an eroded surface rests the 

 Miocene of Lyell and Dall, composed of the osseous conglomerate and 

 the greensand. Overlying these beds is a yellowish greensand, pos- 

 sibly Miocene but probably Pliocene. Fragments of a Pliocene 

 formation have been identified at Gay Head by Dall. There was 

 erosion in the area during or just after Eocene time, again between 

 the greensand and the osseous conglomerate, and between the time of 

 the greensand and the latest Neocene, the yellowish greensand. A 

 bowlder formation now appears, composed of rocks derived from the 

 mainland on the north. It was preceded by local folding of the 

 underlying beds and by erosion along narrow channels, the Miocene 

 being locally swept away. On Block Island the earliest Pleistocene 

 rests upon the Cretaceous at Clay Head, the Miocene being entirely 

 wanting. Succeeding the bowlder deposits there are from twenty-five 



