HILL: GEOLOGY OF JAMAICA. 207 
Vulcanism, which in the preceding Cretaceous epoch was largely domi- 
nant in the Antilles, was now active around the other borders of the 
Caribbean. The great accumulations of volcanic débris which now cover 
the southern ends of the North American Cordilleras, the northern end 
of the Andes, Tehuantepec, the Central American Plateau, the Isthmus 
of Panama, and along the Colombian coast and Windward Islands, are de- 
rived from volcanoes which had their greatest activity during early Eocene 
time, and are now quiescent in the Tehuantepec and Panama regions. 
Stupendous masses of matter were extruded from the earth’s interior, 
and piled upon its crust. The diastrophic effect upon the geography of 
these changes of mass and weight from the interior to the exterior of 
the earth’s surface must have been appreciable. I can only say, for the 
present, that in my opinion that may have in some manner influenced 
the great series of oscillations of level which succeeded the following 
epochs of time from early Tertiary to the present, and which will 
presently be described. 
Contemporaneous with and succeeding this tremendous volcanic revo- 
lution, the relative areas of land and sea were being readjusted. Degra- 
dation and deposition were shifting the load preparatory to a great 
subsidence soon to be initiated in the Atlantic, Gulf, and Antillean 
regions. Immediately after, or during the Cordilleran revolution in 
earliest Eocene time, an epoch of excessive littoral deposition set in, 
marked by great deposits of land-derived sediments, consisting of shallow 
water alternations of non-calcareous, ferruginous, plant-bearing clay, 
sands, and gravel. These were deposited around the perimeters of the 
Gulf and Caribbean, and on the site of the Great Antilles and Barbados. 
Of this nature is the Great Northern Lignite formation of the Gulf 
States, the Culebra formation of Panama and Central America, the 
Parian beds of the South American north goast and islands, the Scot- 
land beds of Barbados, and the Richmond beds of the Great Antilles, — 
all essentially alike in thickness (+ 1,500 feet), character, and arrange- 
ment, and evidently derived from near by lands during a great erosive 
epoch. In North and South America this material was derived from 
the interior bordering regions, but it cannot be said whence came these 
deposits in Central America, the Isthmus, the Antilles, and Barbados, 
unless there were pre-existing lands, such as I have suggested, and 
these must have been of large area to account for the vastness of the 
formations. In North Central America the old Guatemalan nucleus 
could have supplied only a fraction of the sediment. In Panama the 
Source of these formations must have largely been either more extended 
