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1 Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas; present address: Bureau of Economic Geology, P.O. Box X, Austin, Texas 78713-8924; moscardellil{at}mail.utexas.edu
2 Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas; lesli.wood{at}beg.utexas.edu
3 Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin, Austin, Texas; paulm{at}utig.ig.utexas.edu
Lorena Moscardelli is a Ph.D. candidate at the University of Texas and a member of the research team at the Quantitative Clastics Laboratory in the Bureau of Economic Geology, part of the University of Texas at Austin's Jackson School of Geosciences. She received her B.S. degree in geological sciences at the Central University of Venezuela in 2000 and has presented several articles regarding the palynology, stratigraphy, and sedimentology of the Eastern Venezuela Basin. More recently, she does research involving the seismic geomorphology of mass-transport deposits and processes associated with sedimentation along continental margins.
Lesli J. Wood is a research scientist and lecturer in the John A. and Katherine G. Jackson School of Geosciences at the University of Texas at Austin. She holds a Ph.D. from Colorado State University (1992). Lesli has been with the Bureau of Economic Geology in the University of Texas at Austin since 1997, where she directs the Quantitative Clastics Laboratory Industrial Associates program. Her research interests are in outcrop characterization of clastic reservoirs, studies of worldwide large deltaic systems, quantitative seismic geomorphology, and mobile shale basin development. She has authored numerous articles on these subjects.
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 topics 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.
Mass-transport complexes (MTCs) form a significant component of the stratigraphic record in ancient and modern deep-water basins worldwide. One such basin, the deep-marine margin of eastern offshore Trinidad, situated along the obliquely converging boundary of the Caribbean and South American plates and proximal to the mouth of the Orinoco River, is characterized by catastrophic shelf-margin processes, intrusive and extrusive mobile shales, active tectonics, and possible migration and sequestration of hydrocarbons. Major structural elements found in the deep-water slope regions include large transpressional fault zones (i.e., Darien Ridge, Central Range, Los Bajos), along which mobile shales extrude to form sea-floor ridges; fault-cored anticlinal structures overlain by extrusive sea-floor mud volcanoes; shallow-rooted sediment bypass grabens near the shelf break; and normal and counterregional faults. A total of 10,708 km2 (4134-mi2) of merged three-dimensional (3-D) seismic surveys enable sub-sea-floor interpretation of several erosional surfaces that form the boundaries of enormous mass-transport complexes. The data show numerous episodes of MTC developments, which are characterized by chaotic, mounded seismic facies and fanlike geometry. Their extent (up to 2017 km2 [778 mi2]) and thickness (up to 250 m [820 ft]) is strongly influenced by sea-floor topography. Mass-transport flows show runout distances from the source area of 60–140 km (37–86 mi). Depositional architecture identified with these units includes (1) large-magnitude lateral erosional edges, (2) linear basal scours, and (3) side-wall failures. Mud volcanoes act as barriers to cross-slope mass sediment movements and form zones of shadowing on their downslope side that protect those regions from erosion. The subsequent erosional shadow remnants (ESRs) comprise preserved regions of older levee-channel complex sediments and are considered for the first time in this study as potential stratigraphic traps in deep-water deposits. Active tectonism in the region, high sedimentation rates associated with the Orinoco delta system, and abundant potential unstable hydrate suggest the viable presence of several higher frequency mechanisms at work for MTC generation than sea level fluctuations alone.
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