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Abstract
Tectono-stratigraphic Evolution of the Maturin Foreland Basin: Eastern Venezuela
Maria I. Jacome,1 Nick Kusznir,2 Felipe Audemard,3 Steve Flint2
1Universidad Simn Bolvar, Departamento de Ciencias de la Tierra, Baruta, Edo. Miranda, Venezuela
2University of Liverpool, Department of Earth Sciences, Liverpool, U.K.
3Petrleos de Venezuela (PDVSA) Exploracin y Produccin, Caracas, Venezuela
ACKNOWLEDGMENTS
This work forms part of Maria Jacome's Ph.D. research and is funded by Concejo Nacional de Investigaciones Cientficas y Tecnolgicas (CONICIT) and Simn Bolvar University, Venezuela. We are grateful to PDVSA and Simn Bolvar University for providing us with seismic, well-log, and gravity data.
ABSTRACT
New regional interpretation of approximately 2000 km of seismic profiles constrained with more than 20 wells evenly located in the Maturn Foreland Basin in Eastern Venezuela show an extremely thick foreland sediment accumulation, varying from 7 km in the west to 10 km in the east. The interpretation also demonstrates that the total shortening in the seismically imaged portion of the Monagas Foothills and Foreland Thrust Belt decreases from the west (50 km) to the east (35 km), showing no direct relationship between shortening and sediment accumulation. Depth-converted isopach maps show large thicknesses of middle Miocene, Pliocene, and Pleistocene sediments, which is indicative of different episodes of tectonically controlled subsidence. Maximum tectonic-subsidence rates, calculated from decompacted isopach maps, are higher during the Pleistocene (2875 m/Ma) than during the middle Miocene (1260 m/Ma) and Pliocene (1243 m/Ma). Three large depocenters were identified from west (thinnest) to east (thickest), which migrated from northwest (adjacent to the Serrana Thrust Belt) in the middle Miocene to southeast in the present. The thickest Pliocene and Pleistocene depocenters, located in the eastern part of the basin, are not related to thrust-sheet loading, as evidenced by the lack of major active thrust in this area during this time. This shows that the continental lithosphere has subsided by a greater magnitude in the eastern part of the basin than in adjacent areas. Subduction loading associated with the subduction of the South American Continental Plate under the Caribbean could have generated additional subsidence in the Maturn Basin. This is supported by gravity anomaly evidence. Free-air gravity anomalies for the southeastern Caribbean offshore and Bouguer anomalies for Eastern Venezuela show a continuous negative-gravity anomaly extending from the Barbados Accretionary Prism to Eastern Venezuela, suggesting that the Lesser Antilles Subduction Zone may extend southwestward and affect the Maturn Basin.
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