Structure, Architecture and Basin Fill Evolution
of an Actively Evolving Foreland Basin,
Eastern Offshore Trinidad
Emilio J. Garciacaro
UT-DGS MS Candidate
Eastward migration of the Caribbean plate relative to the South American plate is recorded by a 1100-km-long foreland basin which is oldest in the west (Maracaibo basin, 65-55 Ma) and youngest in the east (Columbus basin, eastern offshore Trinidad, 15-0 Ma). The composite foreland basin exhibits a characteristic wedge shape that varies from tens of meters above the South American craton to more than 15 km in thickness to the north adjacent to fold-thrust belts. We have integrated approximately 775 Km of deep 2D seismic lines acquired in the study area as part of the 2004 BOLIVAR project, 8,000 km2 of shallow industry 3D seismic data and published well data from the submarine Columbus basin (CB) to reveal the active tectonic processes that controlled the older, now subaerial and inactive foreland basins to the west. The late Tertiary basin fill of the CB was divided into 7 unconformity-bound sequences which thicken northward to oblique-slip faults bounding the submarine Darien Ridge. Deep wells and seismic data show that the Darien Ridge is composed of an imbricated prism of late Cretaceous and early Tertiary deepwater limestone and clastic rocks that are bounded to the north by an active right-lateral strike-slip fault and metasedimentary rocks of the exotic Caribbean plate. The CB fill itself varies in age from Late Miocene to Recent with a Pleistocene section exceeding 4 km in thickness. Plio-Pleistocene depocenter migration toward the east indicates continuing advance of the Caribbean plate relative to South America during this time. Active mud diapirism in the CB is widespread and is related to overthrusting and loading of upper Miocene - lower Pliocene age shales. 3D visualization of mapped surfaces allow appreciation of the magnitude of Miocene to recent thrusting along the Darien Ridge and control on wedge-shaped sequences.