262 



BULLETIN 103, UNITED STATES NATIONAL MUSEUM. 



enough areas in Cuba to draw inferences as to the physiographic 

 features of the land surface resulting from the erosional activities. 



WEST INDIAN AND PANAMANIAN UPPER OLIGOCENE REEFS. 



ANGUILLA. 



Basic igneous rock above which in places there is some sandstone 

 is exposed below the coralliferous limestone at Crocus Bay and 

 Road Bay. The contact is very clearly one of erosion unconformity. 

 The following is a composite of the sections exposed at Crocus Bay: 



Geologic section at Crocus Bay, Anguilla. 



3. Hard cavernous limestone, with few or no corals 60 feet. 



'2. More or less argillaceous limestone with some beds of harder, purer lime- 

 stone; contains fossil corals from bottom to top, some coral heads as much 

 as 2 feet in diameter; this member subdivisible into subordinate beds 

 about 200 feet. 



1. Yellowish and brownish clay underlain by dark blue-black clay, or sand- 

 stone and conglomerate of igneous material overlying basic igneous rock 

 (exposed at Pelican Point) 5 feet± . 



The exposure at Road Bay is essentially the same as that at Crocus 

 Bay. 



The Anguillan reef was evidently formed during submergence after 

 the subaerial erosion of its basement. 



It should be emphasized that the richly coralliferous limestone is 

 overlain by more massive, harder, limestone in which there are few 

 or no corals ; and that the areal extent of the shoal-water limestone 

 indicates a submarine flat. 



CANAL ZONE . 



The Emperador limestone, according to Doctor MacDonald, lies 

 unconformably on several of the beds belonging to the underlying 

 Culebra formation, and supplies another instance of a fossil coral reef 

 with an unconformable basal contact. 



The stratigraphic relations of the important West Indian and Canal 

 Zone reef corals and coral reefs are summarized in the following 

 table : 



Stratigraphic relations of West Indian and Canal Zone Eocene and Oligocene reef corals 



and coral reefs. 



Age. 



Locality. 



Basal contact. 



Overlying rock. 



Surface of base 

 ment. 





Canal Zone (Em- 

 perador Is.) 

 Anguilla 



Unconformable on 

 Culebra formation. 



Unconformable on 

 igneous rock or on 

 sandstone and con- 

 glomerate. 







Upper Oligocene 



Limestone without 

 or with few corals. 



do 



Submerged flat . 





(Antigua 



Do. 





Porto Rico (Pepino 



formation) . 

 Cuba (Guantanamo) 

 St. Bartholomew... 



do... 



do 



Do. 



Middle Oligocene 



.. .do 





Not known. 



Upper Eocene 



do 



Limestone without 

 or with few corals. 



Submerged flat. 











