HILL: GEOLOGY OF JAMAICA. 27: 
with great rivers which have since been submerged, as alleged by 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 
tho 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 Rica 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. Ifthe 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 fect. 
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 débris 
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 Tehuan- 
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. VI. 
pp. 103-140, Rochester, 1895, 
