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