Pre-Colombian Jamaica: Caribbean Archeology and Ethnohistory

50 / Chapter 4.
Figure 8. Jamaican geology, blocks, and belts.
kindly prepared for use here by Simon Mitchell.) The story can be told in terms
of the standard geological time scale (Porter et al. 1982:Table 8-1). The oldest
deposits in Jamaica are Cretaceous in age, dating from about 100 to 65 million
years ago. They occur in the form of “inliers,” of which there are 27 on the island
(Donovan et al. 1995:Figure 2). They are very variable in size, the largest
being the Central and the Blue Mountain inliers, but they all take the form
of “windows” that have been revealed by the erosion of later deposits that once
covered them. Jamaica during the Cretaceous was part of a volcanic island arc,
in a subduction zone; hence, the exposed deposits are in part terrestrial and
in part of marine origin. The boundary between the Cretaceous and the Tertiary,
at 65 million years ago, is otherwise known as the “ K- T” boundary, the
time when dinosaurs were suddenly extinguished, although as yet none have
been found in Jamaica. The Tertiary lasted until about 2 million years ago, and
during this time the crucial events occurred that determined the present basic
shape of the island.
The early Tertiary, up to the middle Eocene about 45 million years ago, was
a time of serious tectonic movement. It was then, as Robinson has put it, that
“block and belt” features were created that “controlled sedimentation patterns
over the island” for the remainder of the period. The main blocks, from west to
east, are the Hanover, Clarendon, and Blue Mountain blocks. They are separated
from one another by the Montpelier- Newmarket and Wagwater belts re-