Geographie Character: West Indies. 121 
and south”). This continent broke up at the end of the Cretaceous, the chief 
factor in its destruction being the formation of the Caribbean Sea, which con- 
nected with the Pacific Ocean during the lower Tertiary period across the 
submerged Isthmus of Panama. (See the geologic survey-maps in Part III, 
chapter I, Fig. ı—4.) The northern remnant of this continent, consisting of the 
Greater Antilles and parts of present Central America, probably remained a 
unit up to the Eocene for during the Eocene elevation, there was probably 
a landway from Cuba across the Bahama banks to the Floridan area, as 
evidenced by the fact that certain groups of Antillean land mollusks crossed 
that bridge. But at the end of the Eocene and during Oligocene and Miocene, 
the connection between the Greater Antilles and the mainland was severed. 
But it was reestablished toward the end of the Tertiary for before the close 
of the Tertiary period, the West Indian lands were much more extensive than 
now, and the Greater Antilles were once continuous. Geologists have proved 
that during this time the Gulf Stream flowed out of the American Mediterranean 
as now, but through a passage across the northern half of Florida, so that at 
one time southern Florida was West Indian. Furthermore, the great banks of 
the western Caribbean Sea were at that time projections of land probably con- 
necting Central America with Jamaica and possibly Cuba, and in the Miocene 
a land connection was established between North and South America by the 
elevation of the Isthmus of Panama, which was previously in existence and 
connected with the Cordilleran part of the northern continent when the West 
Indian islands during the upper Cretaceous period were in great part beneath 
the sea. 
5. West Indies in general. 
The geologice history of the West Indian islands has been marked by re- 
markable up and down oscillations, so that the land and water areas have 
undergone marked changes in their relative positions. During the end of the 
Cretaceous and the beginning of the Tertiary period, when the great Cor- 
dilleras of North and South America were elevated to approximately their 
present outlines, the known geologic history of the West Indies was just be- 
ginning, for the oldest determined rocks belong to the Cretaceous, Tertiary 
and Pleistocene ages. The Greater Antilles at the close of the Ernkicennis 
period formed a region of volcanic activity for vast heaps of land-derived 
gravel and the conglomerate which make the great thicknesses of old sedi- 
mentary rock in the Antillean mountains lead tp the..conclusion that at the 
beginning of Tertiary time there were land areas in the West Indies. A great 
revolution followed. The pre-existing lands were depressed beneath the sea 
to great depths, in places five miles, or more, until only the high land re- 
1) ORTMAnN, A. E.: The geographical Distribution of freshwater Decapods and its Bearing 
upon ancient er Proceedings American Philosophical Society. XLI: 347. April—De- 
cember 1902 
