Geologically, Suriname is subdivided into a crystalline basement
(80%), and a coastal plain (20%). The Shield area covers more than
80% of the country and forms part of the Guiana Shield, which
stretches between the Orinoco and the Amazon rivers and includes
eastern Venezuela, Guyana, Suriname, French Guyane, and northern
Brazil. The crystalline basement is formed principally of igneous
and metamorphic rocks, while the coastal plain, which stretches
along the northern fringe of the shield area, is exclusively
sedimentary.
Dolerite dykes occur in many places in Suriname, and even dip
under the sediments of the coastal plain. The oldest series (1.6
billion years old) of these dykes are found in the western part of
Suriname. The general trend is Northeast-Southwest, which coincide
with Jurassic rift faults trend (reactivation). The second series
of dolerite dykes (Pigeonite dolerite, 227 million years ago) have
general trend of Northwest-Southeast, and found in eastern
Suriname. They mark the onset of the continental break-up.
Little has taken place in the hinterland of Suriname after the
intrusion of the Pigeonite dolerites; no further orogenic
activities occur. The shield area has been flattened by erosion.