Abstract: Three-Stage Slope Reversal in Northern and Central Trinidad and Its Effect on Megasequences in Cretaceous-Cenozoic Basins

Stephen Babb, P. Mann, Richard T. Buffler

Three distinctive, wedge-shaped megasequences (M1-3) were identified through mapping of seismic sequences tied to well logs in northern Trinidad:

M1: a basal, Late Jurassic-Early Cretaceous passive margin megasequence above an unimaged, rifted? basement corresponds to a wedge-shaped packet exhibiting east to northeast progradation. Four backstep or drowning phases were identified in the prograding sequence. The autochthonous carbonate platform facies in the Gulf of Paria is coeval with slope and basinal rocks uplifted in Neogene time in the Northern Range and Central Range. M1 correlates with the curving continuation of the northeast prograding Mesozoic margin of Guyana that is still subsiding.

M2: a Paleogene megasequence corresponds in northern Trinidad to the feather edge of a southward-thickening clastic wedge. We cannot determine whether the southward tilting controlling M2 formed in an active or passive margin setting. Stratigraphic data constrains uplift during Late Eocene.

M3: a Neogene megasequence corresponds to a wedge-shaped packet of discontinuous (lower part) and continuous (upper part) reflectors exhibiting south and east progradation away from the Northern Range. North and northwest tilting accompanied a main phase of east-west strike-slip faulting from Miocene to Pliocene time with decreasing activity on the Northern Range mountain front to the present. Data from the Gulf of Paria and the Caroni basin suggests that the locus of strike-slip faulting shifted in Pleistocene time from the Northern Range to a parallel but more diffuse zone in the Central Range and Gulf of Paria.

AAPG Search and Discovery Article #90951©1996 AAPG International Conference and Exhibition, Caracas, Venezuela