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1 Eastern Exploration Division, Petróleos de Venezuela, S.A., Puerto la Cruz, Venezuela; duertol{at}pdvsa.com
2 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Road, Building 600, Austin, Texas 78759
3 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Road, Building 600, Austin, Texas 78759; paulm{at}utig.ig.utexas.edu
Leonardo Duerto is a structural geologist and explorationist at the Eastern Exploration Division of Petróleos de Venezuela, S.A. in Puerto La Cruz. He received his M.Sc. degree at the Universidad Central de Venezuela in 1998, where he worked with triangle zone models on the Venezuelan mountain fronts. He is completing his Ph.D. at the University of London. His current research interests focus on complex thrust structures, shale diapirs, and petroleum exploration in the Eastern Venezuela Basin.
Alejandro Escalona is a postdoctoral researcher at the Institute for Geophysics, University of Texas at Austin. He received his Ph.D. in geology at the University of Texas at Austin in 2003, where he focused on stratigraphic and structural evolution of the Maracaibo Basin, Venezuela. He is currently interpreting regional seismic and well data from offshore Venezuela to link offshore and onshore Cenozoic depocenters.
Paul Mann is a senior research scientist at the Institute for Geophysics, University of Texas at Austin. He received his Ph.D. in geology at the State University of New York in 1983 and has published widely on the tectonics of strike-slip, rift, and collision-related sedimentary basins. A current focus area of research is the interplay of tectonics, sedimentation, and hydrocarbon occurrence in Venezuela and Trinidad.
The Maracaibo Basin is a 50,000-km2 (19,305-mi2) topographic depression bounded to the east and south by the Mérida Andes of Venezuela and to the west by the Sierra de Perijá of Venezuela and Colombia. Both uplifted mountain blocks expose Paleozoic basement rocks and Mesozoic–Cenozoic carbonate and clastic rocks that were mainly folded and thrusted by regional shortening in the Paleogene and late Neogene. Using geologic maps, seismic reflection data, and wells from the steep mountain front areas, we test different structural models of how late Paleogene–Neogene convergence is accommodated along subsurface faults and folds at the mountain fronts. Seismic imaging of the deep (>5-km; >3.1 mi) structure of both Maracaibo mountain fronts shows basinward-dipping monoclines with stratal dips ranging from 20° to overturned and an almost complete lack of faulting in the basin-edge monocline or in adjacent, horizontally bedded strata of the Maracaibo Basin. Seismic data reveal the presence of one or more triangle zones at depth along both the Mérida Andes and Sierra de Perijá that exhibit characteristic thrust-wedge geometries. The lower part of the wedge is defined by imbricate thrust faults dipping beneath the mountain block and involving the Paleozoic basement. The upper part of the wedge is defined by a basinward-dipping thrust associated with fault-propagation folds at the surface and an overlain basin-edge monocline. The creation of the steep to overturned dips of the monocline is attributed to the effects of 6–10 km (3.7–6.2 mi) of shortening along the lower zone of imbricated thrust faults. This 6–10 km (3.7–6.2 mi) of shortening, calculated from triangle zones of both the Sierra de Périja and Mérida Andes, is significantly less than regional estimates from 12 to 60 km (7.4 to 37 mi) of shortening inferred by previous workers from regional balanced cross sections that assume low-angle thrust-type geometries. We propose that a pop-up style of deformation related to the inversion of Jurassic rift features may be a more realistic interpretation of the convergent fault systems that have controlled uplift of the Mérida Andes and Sierra de Perijá. Inversion of relatively steep, basement normal faults at the edges of and within both ranges may explain lesser amounts of observed shortening.
This article has been cited by other articles:
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  D. Gorney, A. Escalona, P. Mann, M. B. Magnani, and BOLIVAR Study Group Chronology of Cenozoic tectonic events in western Venezuela and the Leeward Antilles based on integration of offshore seismic reflection data and on-land geology AAPG Bulletin, May 1, 2007; 91(5): 653 - 684. [Abstract] [Full Text] [PDF]
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P. Mann, A. Escalona, and M. V. Castillo Regional geologic and tectonic setting of the Maracaibo supergiant basin, western Venezuela AAPG Bulletin, April 1, 2006; 90(4): 445 - 477. [Abstract] [Full Text] [PDF]
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M. V. Castillo and P. Mann Cretaceous to Holocene structural and stratigraphic development in south Lake Maracaibo, Venezuela, inferred from well and three-dimensional seismic data AAPG Bulletin, April 1, 2006; 90(4): 529 - 565. [Abstract] [Full Text] [PDF]
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M. V. Castillo and P. Mann Deeply buried, Early Cretaceous paleokarst terrane, southern Maracaibo Basin, Venezuela AAPG Bulletin, April 1, 2006; 90(4): 567 - 579. [Abstract] [Full Text] [PDF]
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A. Escalona and P. Mann An overview of the petroleum system of Maracaibo Basin AAPG Bulletin, April 1, 2006; 90(4): 657 - 678. [Abstract] [Full Text] [PDF]
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