Hasley Vincent

Cenozoic sediments in Trinidad record elements of pre-and syn-orogenic siliclastic deposition related to the deformation of a formerly passive, northern South American margin. Prior interpretations regarding the timing of pre- to syn-orogenic sedimentation suggest Late Cretaceous to Early Miocene changes based primarily on lithology and biostratrigraphy. These interpretations vary from "rapid" changes in sea level during the Paleocene to Late Oligocene caused by tectonic uplift, to continuous passive margin sedimentation into the Late Oligocene, influenced by eustatic sea level fluctuations.

The Paleogene was characterized by relatively uniform sedimentary processes and depositional environments, which continued from the Cretaceous and were associated with the delivery of coarse-grained, mature quartz arenites into deep-water basins along a passive margin. Sediments were sourced mainly from the stable South American craton to the south. Changing sedimentological characteristics suggest the incipient input of ayn-orogenic sediments into the basin as early as the Eocene, although the onset of active syn-orogenic sedimentation occurred from Late Oligocene to Early Miocene coincident with deposition of the Nariva Formation and Herrera Sandstone Member. By the Pliocene, lithic arenites were derived from the uplifted Caribbean Mounts to the west and possibly the north and deposited in shallow-water and terrestrial environments. These changes in sediment dispersal patterns in the Trinidad basins were consistent with changes across northern South America related to the uplift of the northern Andean mountains, including the Caribbean Mountains.

Formal stratigraphic units may be better represented when their associated depositional environments are considered. Enigmatic stratigraphic correlations are readily resolved as recurrent depositional events, not deserving of formal stratigraphic distinction. Recommendations are made for formal changes to Paleogene formations on the stratigraphic table of Trinidad.

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Supervisor: Grant Wach