296 BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



Until the specimens of Nummulites from the Bermuda well have 

 been identified with species of known stratigraphic position a more 

 definite statement can not be made. It appears safe to assign an 

 Eocene or pre-Eocene age to the Bermudian volcanic activity. 



The calcareous sediments, therefore, began to accumulate on a 

 submerged volcanic basement in Eocene or lower Oligocene time, 

 and the submergence progressed until the basement, in probably- 

 Miocene time, was entirely blanketed by calcareous deposits 100 

 feet thick, which differ in their physical aspect both from the under- 

 lying nummulitic rock and the overlying organic limestone. This 

 rock is probably in considerable part a chemical precipitate. The 

 well samples indicate no stratigraphic break at either its to p or it 

 base. 



The limestone from a depth of 241 feet to the surface is a shoal- 

 water, organic deposit, in which living species of Foraminifera are 

 abundant. Its age is probably Pleistocene, although the lower part 

 may prove to be Pliocene. The shoal-water nature of the limestone 

 indicates continued slow subsidence. 



The subsidence which apparently had been interrupted by no 

 period of emergence since Oligocene time was succeeded in Pleisto- 

 cene time by uplift to an amount of probably more than 100 feet. 

 All the surface rock of the Bermudas except some in areas of low 

 elevation is considered by the geologists who have visited the islands 

 to be eolian deposits. However, certain of the published illustra- 

 tions suggest that in some exposures there are in the bedding hori- 

 zontal planes intersecting the inclined layers. Cross-bedding between 

 horizontal planes is a structure characteristic of shoal-water or beach 

 deposits but not of eolian deposits. A more critical study of the 

 bedding of the Bermudian rocks may discriminate elevated cross- 

 bedded water-laid and eolian deposits. However this may be, the 

 period of uplift under consideration was the time of the Greater Ber- 

 muda, which has been admirably described by William North Rice, 

 A. Agassiz, and A. E. Verrill. According to the latter, the area of 

 Greater Bermuda was somewhat more than 230 square miles, or about 

 1 1 times that of the present land surface, which is estimated as hav- 

 ing an area of 19 J square miles. 1 The evidence indicates that the 

 elliptical area inclosed by the outer reefs was entirely above sea level, 

 as perhaps also were the surfaces of Challenger and Argus banks. 



The last important change in the relations of sea level was, as 

 Verrill has so ably shown, submergence to an amount of about 100 

 feet, reducing the land area from that of 230 square miles during the 

 period of Greater Bermuda to that of 19 3 square miles, the present 



1 Conn. Acad. Arts and Sci. Trans., vol. 12, p. 52, 1905. 



