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Back to list of UTIG presentations at AAPG's 2004 Annual Meeting
Regional Tectonics, Stratigraphy, Reservoir Characterization, and
Petroleum Systems
in an Eocene Foreland Basin, Maracaibo Basin, Venezuela
Escalona, A.1 and Mann, P.2
1Deparment of Geological Sciences, Jackson School of
Geosciences, The University of Texas at Austin, C1140, Austin, TX
78712-0254, phone: 512-3466881, escalonaa@mail.utexas.edu
2Institute for
Geophysics, Jackson School of Geosciences, The University of Texas at
Austin, 4412 Spicewood Springs Road, Building 600, Austin, TX 78759
The 4-km-thick Eocene clastic section of the Maracaibo Basin has
produced more that 40 billion bbl of oil since the 1920's. This study
uses well and seismic data to image Eocene rocks in the subsurface of
the Maracaibo basin in order to determine the tectonic and eustatic
control on shallow marine reservoirs and petroleum systems. The
Maracaibo foreland basin was filled by Eocene clastic rocks during the
collision between the Caribbean arc system and the passive margin of
northern South America. Eocene thrust faulting affected the area east of
the present-day Lake Maracaibo. The present-day lake area was affected
by flexural faults related to downwarping of the continental crust
towards the collisional area and by north-south strike-slip faults
following the trend of Late Jurassic rifts. 3D data reveal that flexural
and strike-slip faults on the Eocene shelf controlled the distribution
of fluvial and tide dominated delta systems. A major angular
unconformity spanning the interval from middle Eocene to Oligocene
truncates folded and faulted Eocene rocks. This so-called "Eocene
unconformity" is interpreted as a rebound effect related to SE migration
of post-Eocene thrusting and crust relaxation of the present-day lake
area. The Eocene unconformity forms a major seal on hydrocarbons
generated by late Cretaceous source rocks during the Paleogene.
NS-trending structural highs produced during Eocene provide traps for
hydrocarbons moving updip along steep-dipping faults. In some areas,
continued displacement on these faults and EW shortening from early
Miocene to present time across the lake area allowed hydrocarbons
migration into Miocene reservoirs.
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