HILL: GEOLOGY OF JAMAICA. 207 



Yulcanisin, 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 debris which now cover 

 the southern ends of the ^^orth 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 chanofes 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 cla}'', 

 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 coast and islands, the Scot- 

 land beds of Barbados, and the Richmond beds of the Great Antilles, — 

 all essentially ahke 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 tliese 

 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 



