TITLES AXD ABSTRACTS OF PAPERS 217 



ing. Although there are corals in the exposed sediments of Oligocene and 

 Miocene age, and corals were therefore constructional agents during those 

 epochs, their work, as compared with that of other agents, was of minor 

 importance. If the work of these organisms in forming deposits concealed 

 under water can be evaluated by their work in deposits exposed to view, the 

 conclusion would be draw^n that they played only a minor role in the formation 

 of the Virgin Bank, There is as yet no evidence showing intense deforma- 

 tion during later Oligocene time in the Virgin Islands and Porto Rico, such 

 as is known to have taken place in Santo Domingo, 



(6) Subsequent to early Miocene time there has been uplift, greater along 

 the axis of Porto Rico and the Virgin Bank than on the flanks, bringing 

 Miocene and older Tertiary sediments, in places where they are present, above 

 sealevel. The Tertiary sediments are tilted and gently flexed, but they have 

 not been deformed as the Upper Cretaceous deposits. It is about this time 

 that the land connections permitting migration of land animals from. Anguilla 

 to Porto Rico, Haiti, and Cuba seem to have existed. Saint Croix seems to 

 have been connected with Anguilla, Saint Martin, and Saint Bartholomew, 



(7) The period of high stand of land was followed by an episode of block- 

 faulting, such as I have several times described recently. By faulting, Ane- 

 gada Passage between the Virgin Bank and Anguilla was produced, and the 

 islands assumed very nearly the outlines and arrangements of today. 



(8) Subsequent to the episode of faulting, there was emergence of the land 

 and terracing of the margins of the Virgin Bank, followed by submergence. 

 In places in Porto Rico and along the Cordilleras reef, which extends eastward 

 from the northeast corner of Porto Rico, there has been local emergence due 

 to differential crustal movement. 



(9) The living coral reefs on the Virgin Banks are growing on an extensive 

 flat in a period of geologically Recent submergence. This flat is geologically 

 an old feature. Its origin, in large part at least, may reasonably be attributed 

 to the long period of erosion following early Tertiary mountain-making. 



There was then presented a stratigraphic paper transferred from the 

 program of the Geological Society of iVmerica : 



GEOLOGIC RECONNAISSAyCE IN SANTO DOMINGO^ 

 BV C. WYTHE COOKE 



(Ahstnict) 



During the spring and early summer of 1919 a preliminary reconnaissance 

 of Santo Domingo was made for the Dominican Government by T. W. Vaughan, 

 D. D. Condit, C. P. Ross, and tlie writer, under the direction of Dr. Vaughan. 

 The central mountain system was crossed by three routes and as much of 

 the areas north and south of it was examined as was feasible in the time 

 allotted. Many fossils, chiefly from the Tertiary formations, were collected, 

 and liave been distrilmted to specialists for study. The data obtained, al- 



I'ublished by permission of tht> military goveruor of the Domiaicaa Republic. 



