HILL: GEOLOGY OF JAMAICA. 217 



with great rivers which have since been submerged, as alleged bj J. W. 

 Spencer.^ In the eastern and southern United States, Central America, 

 Panama, and the Antilles, extensive degradation occurred, marked first 

 by deep incisions of canyons on rapidly rising land and base-levelling of 

 the borders, and next by deposition of the aggradational material over 

 the recently formed plains. This epoch apparently corresponds with that 

 which has been described as the Lafayette by McGee, the time of which 

 was before the close of the Pliocene. 



In the Antilles proper, and on both coasts of Costa Eica and Central 

 America, this movement is recorded by a number of long continuous 

 base and beach level terraces, the highest of which are 600 feet above 

 sea level in the Antilles, as exemplified in the Yumuri terrace of eastern 

 Cuba and about 200 feet in the Panama-Costa Rican region, as seen in 

 the Monkey Hill and Naos benches of Panama. There are no bench 

 marks in the Windward region by which this movement can be cor- 

 related there, the field of elevation probably not having reached so far 

 to the eastward. If the Panama and Yumuri levels are synchronous, — 

 and concerning their identity we are not yet fully satisfied, — there is 

 evidence of a considerable difference in amplitude of uplift between the 

 two points, the greatest movement having been in that portion of the 

 Antilles adjacent to the Windward Islands, there exceeding that of 

 the Panama coast by some 500 feet. 



During this epoch vulcanism was continuously active in all the present 

 regions of living volcanoes, as well as in the Cordilleran region of the 

 United States, although expiring in the latter. 



The margins of the present Antilles and Caribbean and Gulf main- 

 lands were flooded by the seas in late Pliocene time, and subsidence 

 may be presumed. The continental coastal plains of south Florida, 

 Mexico, Yucatan, Costa Rica, and Trinidad, the lowlands of the pre- 

 expanded Antilles, and the Atlantic margin of the Windward platform, 

 were veneered during Pliocene time with a coating of oceanic debris 

 composed of shells and calcareous muds. How the western Gulf region 

 was affected during this epoch cannot be stated with clearness at present, 

 but from the fact that the rivers of the back coast country of Texas were 

 partially drowned and partially refilled with alluvial sediments, it is 

 probable that that region was much lower than at present. In Tehnan- 

 tepec and Costa Rica the Pliocene marine deposits indent the Gulf 

 and Caribbean coasts for a considerable distance inland. During: this 



1 Reconstruction of the Antillean Continent. Bull. Geol. Soc. Amer., Vol. VL 

 pp. 103-140, Rochester, 1895. 



