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The AAPG/Datapages Combined Publications Database

GCAGS Transactions

Abstract


Gulf Coast Association of Geological Societies Transactions
Vol. 56 (2006), Pages 577-577

Abstract: Control of Upstream Variables on Late Quaternary Incised-Valley Evolution along the Northern Gulf of Mexico Margin

Christopher Robin Mattheus1, Antonio B. Rodriguez2

Abstract

It is established that sea level along the northern Gulf of Mexico margin fell to ~120 m below present day level during the Last Glacial Maximum (~22-17 ka), exposing the continental shelf and promoting fluvial incision. The incised-valley systems formed during this lowstand in sea level have been well constrained by seismic and lithologic studies, aided by 14C dating techniques. However, a comparative study has not been attempted to determine relative controls of upstream (climate and drainage-basin characteristics) and downstream (fluvial and shelf gradients, rate and magnitude of base-level fall) controls on incised-valley evolution. To address this, incised-valley dimension was calculated for eight Oxygen Isotope Stage 2 incised-valley systems from core and seismic data at locations close to the highstand shoreline of the previous sequence along the margin. Studied systems cover a region presently characterized by steep precipitation gradients, are distinguished by drainage basins that vary in size by three orders of magnitude, and extend across a continental shelf that varies along strike in width (80-160 km) and gradient (1.0-2.0 m/km). Linear relationships between drainage-basin area and incised-valley cross-sectional area and width suggest a strong correlation between discharge and incised-valley dimension for systems along the northern Gulf of Mexico margin. These data suggest that the level of variability along the margin is not unique and comparison of incised-valley dimension therefore yields insight into respective drainage-basin sizes and/or climate gradients. Although the base-level fall promoted fluvial incision, incised-valley dimension was controlled by upstream variables.


 

Acknowledgments and Associated Footnotes

1 949 Lakeside Dr., McCalla, AL 35111

2 3431 Arendell St., Morehead City, NC 28557

Copyright © 2007 by The Gulf Coast Association of Geological Societies