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Abstract

AAPG Bulletin, V. 91, No. 5 (May 2007), P. 653-684.

Copyright copy2007. The American Association of Petroleum Geologists. All rights reserved.

DOI:10.1306/11280606002

Chronology of Cenozoic tectonic events in western Venezuela and the Leeward Antilles based on integration of offshore seismic reflection data and on-land geology

David Gorney,1 Alejandro Escalona,2 Paul Mann,3 M. Beatrice Magnani,4 BOLIVAR Study Group 5

1Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Road, Bldg. 600, Austin, Texas 78759; present address: Marathon Oil Company, 5555 San Felipe, Houston, Texas 77056; [email protected]
2Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Road, Bldg. 600, Austin, Texas 78759; present address: Institute for Petroleum Technology, University of Stavanger, 4036 Stavanger, Norway; [email protected]
3Institute for Geophysics, John A. and Katherine G. Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Road, Bldg. 600, Austin, Texas 78759; present address: Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 10100 Burnet Road (R2200), Austin, Texas 78758-4445; [email protected]
4Department of Earth Science, Rice University, Houston, Texas; present address: Center for Earthquake Research and Information (CERI), University of Memphis, 3876 Central Avenue, Memphis, Tennessee 38152; [email protected]
5Alan Levander, Gail Christeson, Paul Mann, Colin A. Zelt, M. Beatrice Magnani, Michael Schmitz, Stoney Clark, Maria C. Guedez, Maximiliano Bezada, Yemi Arogunmati, David Gorney, Trevor Aitken, and Amanda Beardsley

ABSTRACT

Newly acquired, deep-penetration Broadband Onshore-Offshore Lithospheric Investigation of Venezuela and the Antilles Arc Region seismic reflection data from offshore western Venezuela (Bonaire Basin) and around the Leeward Antilles are combined with existing geologic and geophysical data sets to examine the chronology of Late Cretaceous–Cenozoic tectonic events in this part of the Caribbean–South American plate boundary zone. These tectonic events have controlled the maturation and structural trapping of known hydrocarbons in the offshore Bonaire Basin and the adjacent onland Falcoacuten Basin. We infer three tectonic phases that are constrained using these combined data sets. (1) The late Eocene–early Oligocene, north-south opening of the 3–6-km (1.8–3.7-mi)-thick Falcoacuten-Bonaire Basin occurred along east-west–striking normal fault systems that have locally been inverted by later tectonic phases. These Paleogene normal faults rifted the Upper Cretaceous arc crust and Paleogene marine depositional sequences within the offshore Bonaire Basin. (2) Northwest-striking normal faults crosscut the older normal faults of the Bonaire Basin and Leeward Antilles and form deep, submarine rifts that contain up to 4 km (2.5 mi) of sedimentary fill and form deep-water channels between islands of the Leeward Antilles. Offshore well data and age of onshore sediments in the Falcoacuten Basin indicate that this second phase of rifting occurred mainly during the late Oligocene to early Miocene and remains active to the present. (3) Inversion of the subaerial Falcoacuten Basin commenced during the middle Miocene. This inversion phase is reflected in the present-day pattern of an east-northeast–trending fold-thrust belt that can be traced over 200 km (124 mi) along strike in the Falcoacuten Basin. A second offshore fold-thrust belt (La Vela) can be traced over a distance of 175 km (108 mi) along strike and parallel to the northeast-trending Falcoacuten Basin coast. Restoration of imbricate thrusts seen on seismic lines perpendicular to the La Vela fold-thrust belt indicates a minimum of 7 km (4.3 mi) of northeast-southwest–directed, thin-skinned shortening. Geochemical work indicates that source rocks for scattered occurrences of hydrocarbons in the Falcoacuten Basin and its coastal zone are Paleogene and Miocene marine shale. Reservoir rocks are Tertiary marine sandstone and shale deposited in Paleogene rifts formed during the first tectonic phase in the late Eocene to early Oligocene. Structural traps were formed by thrusting during the second tectonic phase in the late Oligocene to early Miocene.

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