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Abstract

The sections presented are located on the continental shelf off the northeastern coast of South America. The strata under discussion belong to the sedimentary fill of the Guyana coastal basin which, together with the Eastern Venezuela/Trinidad basin further to the north, frames the cratonic Guyana shield (Figure 1). Primary sedimentary features which can be seen in the sections are shelf edges, foreset bedding, disconformities, fractured and folded allochthonous masses, and reefal bodies.

The Guyana coastal basin lies adjacent to the Western Atlantic passive margin. The tectonics are predominantly controlled by a gradual subsidence of the Guyana shield toward the spreading zone of the oceanic floor of the Western Atlantic. Spreading seems to have started in Late Jurassic time. The oldest known deposits are Upper Jurassic carbonaceous sandstones which initiate a series of mainly transgressive cycles commencing with a deposition of predominantly coarser clastics, and gradually changing into carbonates.

This cyclic sedimentation continues from Lower Cretaceous until middle Tertiary time when, finally, a large carbonate platform was formed. During Oligocene time a major regression took place which resulted in substantial erosion and destruction of parts of the carbonate platform and, there after, in a progradational fill of the seaward basin with mainly unconsolidated clastics in front of the remnants of the coastal platform (Figures 1, 5, and 8).

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