Structure, Architecture and Basin Fill Evolution
of an Actively Evolving Foreland Basin,
Eastern Offshore Trinidad
Emilio J. Garciacaro
UT-DGS MS Candidate
Abstract
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.