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Subsidence in the Northwestern Gulf of Mexico: A Late Pleistocene Texas Perspective

Simms, Alexander *1; Anderson, John 2; DeWitt, Regina 3; Lambeck, Kurt 4
(1) Department of Earth Science, University of California, Santa Barbara, Santa Barbara, CA.
(2) Department of Earth Sciences, Rice University, Houston, TX.
(3) Department of Physics, East Carolina University, Greenville, NC.
(4) Research School of Earth Science, Australian National University, Canberra, ACT, Australia.

Current IPCC projections of sea-level rise over the next century range from 0.18 to 0.59 m threatening many low-lying coastlines across the globe. In many areas this problem will be exacerbated by subsidence caused by Holocene compaction, anthropogenic-related subsidence due to groundwater and petroleum extraction, tectonic subsidence, or crustal loading. Deciphering the relative contributions of these mechanisms on relative sea-level change remains an important step for planning proper mitigation strategies. One area that is particularly vulnerable to subsidence and sea-level rise is the northern Gulf of Mexico. In this study we use the differential elevations of modern barrier islands and their marine isotope stage 5e (MIS5e) equivalent geomorphic features to determine the background rates of subsidence along the Texas coast over the last 120,000 years. We first obtained optically stimulated luminescence ages of features long interpreted to be MIS5e but until now, have remained undated. We then use a digital elevation model (DEM) to calculate the difference in elevations between the modern and MIS5e barrier shorelines. This difference is corrected for glacial-hydro-isostatic contributions since MIS5e to determine the long-term subsidence rate for the northwestern Gulf of Mexico over the last 120,000 years. Our analysis shows spatial variability in the rate of subsidence that generally decreases to the south and west along the Texas coast. The lowest rates of subsidence observed were 0.04 mm/yr at our furthest inland site. The highest rates of subsidence observed were around 0.1 mm/yr near the Brazos Delta.
 

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California