GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 



275 



18 fathoms, and indicates submergence of about 120 feet or 20 

 fathoms. (See fig. 11 below.) 



Barrier coral reefs occur around Antigua off the mouth of Nonsuch 

 Bay, off the southwest angle of the island, and there is a discon- 

 tinuous barrier off the west side of the island. There are other reef 

 patches, some of which are almost barriers. Barbuda has barrier 

 reefs, Cobb and Goat reefs, off its northern end. 



These reefs of Antigua and Barbuda occur on a platform which has 

 been submerged. That the platform or flat lying between Antigua 

 and surrounding Antigua is in origin independent of the corals growing 

 on itsjsurf ace is shown not alone by its continuity irrespective of 

 the presence of corals. That a land area existed between Antigua 

 and Barbuda in Pleistocene time is clearly shown by the land mol- 

 lusca; while the submerged steep slope or scarp shows that the flat 



SOUTHEAST COAST OF ANTIGUA 



~ 6^ /77/\ >• 



NORTH COAST OF 

 ST. THOMAS 



HAVANA HARBOR 

 showing depth of filled 

 channel in harbor 



MOSQUITO BANK 



FlG. 11.— SUBMARINE PROFILES OFF WEST INDIAN ISLANDS AND ACROSS MOSQUITO BANK. 



existed and was marginally cut by the sea while it stood about 120 

 feet higher than at present. 



ST. MARTIN PLATEAU. 



J. W. Spencer has applied this designation to the plateau on which 

 St. Bartholomew, St. Martin, and Anguiila stand. This plateau, as 

 bounded by the 100-fathom curve, is irregular in shape and is 75 

 miles long by 45 miles wide. The maximum depth of water between 

 St. Bartholomew and St. Martin is 16 fathoms and between St. 

 Martin and Anguiila 14 fathoms. (See text fig. 12.) 



The shore fine of St. Bartholomew is indented, the indentations are 

 usually divided by beaches into an inner or lagoon part and an outer 

 bay or harbor part (pi. 68, figs. C, D). The beaches may have 

 been elevated between 3 and 5 feet. The lagoons behind the beaches 



