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Quantitative seismic geomorphology of a Quaternary leveed-channel system, offshore eastern Trinidad and Tobago, northeastern South America

¹ Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Texas 78713-7508; lesli.wood{at}beg.utexas.edu
² Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Texas; present address: EnCana Oil and Gas Inc., Denver, Colorado

Lesli Wood is a senior research scientist at the Bureau of Economic Geology in the University of Texas (UT), Jackson School of Geosciences. She received her M.S. degree in geology from the University of Arkansas (1988) and her Ph.D. in earth resources from Colorado State University (1992). Upon graduation, she worked for Amoco for 5 years and 13 days and moved to Austin in 1997. She currently runs the Quantitative Clastics Laboratory Industrial Associates program at UT. Her research interests include quantitative seismic geomorphology, martian and Earth deltas, shale diapirs, and clastic margin studies.

Kristine Mize-Spansky received her B.S. degree in geology from the University of Illinois at Urbana-Champaign (UIUC) in 2000. During her time at UIUC, she worked as an intern at the Illinois State Geological Survey. She received her M.S. degree in hydrogeology from Clemson University in 2002, then completed her M.S. degree in geology from the University of Texas at Austin in 2004. She has been a geologist with EnCana Oil & Gas (U.S.A.) Inc. in Denver, Colorado, since 2005.

ABSTRACT

This article documents the application of techniques in quantitative seismic geomorphology in quantifying the morphometrics and architecture of deep-marine leveed-channel systems within an about 10,000-km² (3861-mi²) study area offshore eastern Trinidad, West Indies. The principal goal of this study is to assess the relationship, if any, between sea-floor morphology and channel and levee architecture and morphology toward the development of predictive models of reservoir distribution and channel-system morphology that might be applicable to the interpretation of these types of deposits in similar settings around the world. Seven channel systems, classed into three types, within a 200-ms interval of data immediately below the modern sea floor provided the data for analysis. Results suggest that local structural features and sea-floor slopes exert more influence on channel morphology and occurrence than do eustatic sea level factors. Sinuosities, channel widths, meander-belt widths (MBWs), and meander-arc height (MAH) all increase as the channel systems age. Slope and sinuosity are directly related to one another, with sinuosity increasing as slope increases. Levee heights and widths increase downslope in areas of lower slope gradients. Channel sinuosity, MAH, and MBW increase immediately downslope from localized diapirs, and channels appear to migrate updip over time because of regional inflation of distal arc prism areas. Diapirs and uplifts cause overbank splays to become more confined and cause levees to shorten and taper rapidly. Regional tilt to the south appears to affect accommodation, creating a sink for sediments near the toe of slope. Regional tilt also affects flow processes in the channels, causing an increased overbanking of flows toward the south, away from the plate margin, resulting in higher, wider levees on the south sides of the channels.