REVIEWS 819 
late Oligocene or Miocene. ‘The formation was deposited after a sub- 
sidence which followed the uplift and extensive erosion of the White 
Limestone. The break between it and the White Limestone is, there- 
fore, a great one, and on general grounds it would seem more in 
accord with modern classification to make the break between these two 
formations the division between the Oligocene and Miocene than to 
place it in the Oligocene. The Bowden formation has a thickness of 
something like 250 feet. Its outcrop consists of a fringe around the 
older plateau region, and it is, in turn, bordered by still later and 
lower-lying formations. ‘The Bowden formation is made up of various 
sorts of sedimentary rock. 
The next succeeding formations are classed as Pliocene. They are 
composed of marl and limestone of marine origin (Manchioneal), and 
of slight thickness, and of gravels from the uplands. The gravels are 
in part estuarine, in part subaérial, and in part littoral. ‘The Pliocene 
formations have relatively slight surface development, though consider- 
able areas in the vicinity of Kingston are covered by them. 
Among the Pleistocene formations are beds of reef rock, ten to 
forty feet in thickness. They range in elevation from sea level up to 
seventy feet. ‘They lie on eroded land surfaces, and their relations 
are significant of the movements to which the land had been subject 
before their formation. Other Pleistocene formations consist of chalky 
marls at low levels near the coast. Here belongs especially the Fal- 
mouth formation which rarely occurs higher than fifteen feet above the 
sea. ‘The Falmouth formation is nothing more than a series of uncon- 
solidated sea muds, probably synchronous with the younger elevated 
coral reefs. Among the latest formations are the alluvial deposits in 
valleys about the shores. In Montego Bay there are low islands which 
owe their origin primarily to mangroves. 
There are some igneous rocks on the island. The oldest are the 
bowlders of andesite in the Blue Mountain series. The source of this 
igneous matter is unknown. There are mid-Tertiary igneous rocks in 
the form of dikes, laccoliths, etc., composed of hornblende-diorite, and 
granite-porphyry. These intrusive rocks affect the Blue Mountain 
series, and extend upward into the White Limestone above, but 
are found only in the eastern third of the island. In a single locality 
on the north coast near the east end of the island there is eruptive 
amygdaloidal basalt. There is everywhere more or less metamorphism 
in association with the igneous rocks. 
