﻿GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 303 



Willis has directed attention to two areas of submergence by down- 

 warping along the Argentine coast, namely, the embayment of the 

 Rio de la Plata and Bahia Blanca;^ but Barrell is of the opinion, from 

 the character of the submarine profiles, that there has been sub- 

 mergence of the coast subsequent to the warping.^ That there has 

 been in late geologic time a rising of ocean level on the Argentine 

 coast seems a justified deduction. 



ATLANTIC COAST OF THE UNITED STATES NORTH OF FLORIDA. 



That the last shift in position of strand line from the Georgia- 

 Florida fine at least to Narraganset Bay has been by submergence is 

 so clearly shown by drowned stream mouths, resulting in estuaries 

 and harbors, is so well known to geologists that no detailed presenta- 

 tion of evidence is necessary. Northward from near Boston there 

 has been subsequent to submergence, emergence, probably due to 

 crustal rebound after deglaciation and rehef of the pressure exerted 

 by the superincumbent continental glaciers. 



TYPES OF WEST INDIAN AND CENTRAL AMERICAN LITTORAL AND SUBLITTORAL 

 PROFILES AND THEIR RELATIONS TO CORAL REEFS. 



In my paper on littoral and subhttoral physiographic features of 

 the Virgin and northern Leeward islands,^ I pointed out that there 

 are four types of subhttoral profiles in the West Indies (see fig. 19) 

 as follows : (1 ) That found off volcanic islands, such as Saba, into the 

 sides of which the sea has cut relatively narrow platforms; (2) fault 

 plane profiles, such as the north side of St. Croix; (3) wide undersea 

 flats, where planation agencies have long been active, as off Anguilla 

 and north of St. Thomas; (4) submarine banks, such as Saba, Pedro, 

 and RosaUnd, which have no bordering land, and whose upper sur- 

 faces lie between 9 and 30 fathoms below sea level. All of these 

 areas have undergone geologically Recent submergence. Where 

 do the offshore reefs occur ? 



There is no barrier reef on the fault slope on the north side of 

 St. Croix. No reef started as a fringing reef, then increased in thick- 

 ness and grew seaward so as to form a prism of coral-reef rock 

 and material caught behind the reef, so as to become converted 

 according to the Darwinian hypothesis into a barrier reef; but tiiere 

 is a barrier off th^ south side of the island, where gently dipping Hme- 

 stones pass below the sea and produce a platform on the surface of 

 which at the proper depth a barrier reef has formed. Off the fault 

 shore of the south side of Oriente province, Cuba, there is no barrier 

 reef, but farther west, between Cape Cruz and Trinidad where there 



1 Willis, Bailey, Geologic notes, in Hrdlicka, A., Early man in South America, Bur. Amer. Ethn. Bull. 

 52, pp. 16-18, 1912. 



2Barrell, Joseph, Factors in movements of the strand line and their results in the Pleistocene and post- 

 Pleistocene, Amer. Journ. Sci., ser. 4, vol. 40, p. 6, 1915. 



3 Washington Acad. Sci. Journ., vol. 6, pp. 53-66, 1916. 



