--> --> Abstract: Neotectonics of the Mississippi River Delta Region, by Mark A. Kulp and Paul D. Howell; #90914(2000)

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Mark A Kulp1, Paul D. Howell1
(1) University of Kentucky, Lexington, KY

Abstract: Neotectonics of the Mississippi River delta region

Stratigraphic data from the Upper Quaternary section of the Mississippi River delta region has been accumulating for over fifty years in a variety of formats. Collectively, these data provide an opportunity to identify regional patterns and rates of Holocene subsidence and determine the contribution of known subsidence mechanisms to these identified subsidence trends. This study integrates previously developed data to regionally correlate the Late Wisconsin to Holocene transgressive and highstand sedimentary sequence overlying the Late Wisconsin unconformity below the deltaic plain and bordering continental shelf in 199 offshore borings, 647 onshore borings, and numerous, widely-spaced, high-resolution, seismic profiles from the continental shelf. Excellent correlation of the sedimentary sequence among datasets has been found to exist which, coupled with more than 300, radiocarbon-dated peats has enabled construction of regional isopachous and structural elevation maps and cross sections detailing the Late Quaternary stratigraphic framework. Trends in structural elevation and thickness of sedimentary sequences on the eastern and western continental shelf indicate that vertical motion related to faulting and halokinesis is laterally restricted to within several kilometers of the structural feature and typically less than 20% of the total stratigraphic thickness. Detailed cross sections reveal similar findings onshore. High subsidence rates above compaction-prone sediments suggests that sediment dewatering is a more dominant factor in regional subsidence trends and primarily operative within 2,000 years of deposition. A long wavelength subsidence pattern with a maximum rate of 2 mm yr-1 is believed to reflect the contribution of isostatic loading by sediments and eustatic rise.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana