The geology of the Grenadines can be
divided into two main areas of interest. First are the reefs and second
is the volcanics.
The reefs receive world wide attention
as some of the most beautiful and healthy reef ecosystems around the world.
The classic reef ecosystem found in the Grenadines is located in the Tobago
Cays. On the eastern side of the Tobago Cays is the Horse-shoe Reef. The
reef constantly has waves breaking over it, and there are strong currents
which flow over and around the reef. Further discussion of the Tobago Cays
reef can be found in our Transect Project.
The volcanism is responsible for the
genesis of the islands. The Grenadines are dominated by basalt and basaltic
andesite volcanism. These lavas differ from those of St. Vincent to the
north, and the famous Soufriere volcano. They differ in that the Grenadines
basalts are rich in incompatible elements while St. Vincent's basalts are
low in incompatible elements.
There is a stratigraphic range from
the Middle Eocene to Recent found in the Grenadines. This is the largest
stratigraphic range found in the Lesser Antilles. In general the Grenadines
are more closely related to Grenada than St.Vincent. This is explained
by the fact that there is a continuous shallow bank between the Grenadines
and Grenada. In the Grenadines the Lesser Antilles older arc is exposed.
It has an age of Eocene to Oligocene. Also in the the Grenadines the younger
arc of the Lesser Antilles is superimposed on the older arc. It has an
age of Miocene to Recent.
Study of Bequia