• journal_title：Journal of Sedimentary Research
• Contributor：Christopher R. Mattheus ; Antonio B. Rodriguez ; D. Lawrence Greene Jr. ; Alexander R. Simms ; John B. Anderson
• Publisher：SEPM Society for Sedimentary Geology
• Date：2007-
• Format：text/html
• Language：en
• Identifier：10.2110/jsr.2007.022
• journal_abbrev：Journal of Sedimentary Research
• issn：1527-1404
• volume：77
• issue：3
• firstpage：213
• section：RESEARCH ARTICLES: FLUVIAL SEDIMENTATION

It is well documented that sea level fell during the Last Glacial Maximum, shifting graded-stream profiles out of equilibrium and causing rivers to incise into continental shelves. Although incised valleys have been heavily researched, the interplay between upstream and downstream controls on incised-valley dimension are not well constrained. To address this lack of understanding, we examined the cross-sectional dimension of nine incised valleys located across the northern Gulf of Mexico margin and bounded by the sequence boundary associated with the last sea-level lowstand. These incised valleys are distinguished by drainage basins that vary in size by three orders of magnitude, cover a margin that presently has a steep climate gradient, and extend across a continental shelf that varies along strike in width and gradient.

Incision depths vary for valleys that have similar gradient profiles but different drainage-basin areas, suggesting significant control of upstream variables on incised-valley morphology. Additionally, these data show a strong linear correlation between drainage-basin area and incised-valley cross-sectional area. This suggests applicability of the empirically derived relationship between modern discharge and cross-sectional channel area to incised valleys when compared at the maximum highstand shoreline of the previous sequence. Incised-valley dimension adjusts over a longer period than the lowstand and is in equilibrium with drainage-basin area, which is considered a proxy for long-term discharge. Although base-level fall promotes incision, upstream variables control incised-valley dimensions.