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1 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, 4412 Spicewood Springs Road, Building 600, Austin, Texas 78759; escalona{at}ig.utexas.edu
2 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
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 the stratigraphic and structural evolution of the Maracaibo Basin, Venezuela. He is currently interpreting subsurface seismic and well data from offshore Venezuela to link offshore and on-land 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.
Eocene clastic rocks of the Maracaibo Basin were deposited in an asymmetrical foreland basin formed during the oblique Paleogene collision between the Caribbean and South American plates. In this study, we use more than 300 wells and 2000 km2 (772 mi2) of seismic data in the central Maracaibo Basin to produce a detailed sequence-stratigraphic interpretation of the Eocene Maracaibo foreland basin.
The base of the Eocene stratigraphic succession in the central Maracaibo area is characterized by an approximately 250-m (820-ft)-thick, aggradational succession of fluviodeltaic sandstone overlain by an approximately 600-m (1968-ft)-thick retrogradational succession of shallow-marine shale and sandstone containing minor progradational units. The upper part of the foreland basin sequence is marked by an approximately 100-m (328-ft)-thick aggradational succession of fluviodeltaic sandstone. In the approximately 1000-m (3280-ft)-thick Eocene section, we interpreted 17 parasequence sets, 6 genetic sequences, and 1 depositional sequence. Only one classic sequence boundary was interpreted within the Eocene section that marks the boundary between the retrogradational shallow-marine section and the overlying aggradational fluviodeltaic succession. Based on the stratigraphic architecture and thickening trends of several of the parasequence sets, we conclude that the main source of clastic sedimentation was located on the South America craton south of the Maracaibo Basin, instead of along the thrusted, north-northeastern margin of the basin as proposed by previous workers.
A lack of recognition of classic sequence boundaries suggests that Eocene clastic rocks of the central Maracaibo foreland basin were not subaerially exposed during most of the Eocene, and that their stratigraphic architecture was controlled by tectonic subsidence related to thrusting along the northeastern edge of the foreland basin. Eustasy was not an important control on the stratigraphic evolution of the foreland basin until its middle Eocene aggradational period that marked the end of foreland basin subsidence. Well logs and three-dimensional seismic data show that depositional environments on the Eocene delta plain and shelf of the central Maracaibo foreland basin were dominated by fluvial and tidal processes that are similar to modern depositional processes of the Orinoco delta in eastern Venezuela.
This article has been cited by other articles:
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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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A. Escalona and P. Mann Tectonic controls of the right-lateral Burro Negro tear fault on Paleogene structure and stratigraphy, northeastern Maracaibo Basin AAPG Bulletin, April 1, 2006; 90(4): 479 - 504. [Abstract] [Full Text] [PDF]
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J. I. Guzman and W. L. Fisher Early and middle Miocene depositional history of the Maracaibo Basin, western Venezuela AAPG Bulletin, April 1, 2006; 90(4): 625 - 655. [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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A. Escalona Petrophysical and seismic properties of lower Eocene clastic rocks in the central Maracaibo Basin AAPG Bulletin, April 1, 2006; 90(4): 679 - 696. [Abstract] [Full Text] [PDF]
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