Late Pleistocene paleosols in the lower Mississippi River Valley: Documentation of regional base level change

Conference · Wed Jan 01 00:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5808151

Autin, W J ^[1]; Aslan, A ^[2]

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1. Louisiana Geological Survey, Baton Rouge, LA (United States)
2. Univ. of Colorado, Boulder, CO (United States). Dept. of Geological Sciences

Late Pleistocene alluvial paleosols of the Mississippi River are developed in constructional fluvial deposits of ancestral meander belt, overbank, and flood basin deposits. At the type section of the Mt. Pleasant Bluff Alloformation of the Prairie Complex, the upper paleosol developed between 27 and 22 ka as part of a sequence of stacked paleosols that reflect cycles of an abandoned channel fill draped by proximal overbank deposits. Peoria Loess and mixed loess accumulated between 22 and 12 ka to bury the alluvial sequence. Base level lowering coincided with Late Wisconsinan glaciation and a minimum sea level at about 20 to 18 ka. Subsequent Holocene alluvial aggradation and valley wall plantation produced the present terrace escarpment. Soil morphology of the Mt. Pleasant Bluff Alloformation reflects two stages of soil development related to the removal of soils from an active flood plain environment to a terraced landscape position. Based on comparison with Holocene analogs, the first stage of pedogenesis in an active flood plain environment produced a hydromorphic soil as evidenced by color mottles, iron and carbonate nodules, and moderately developed B and C horizons. The second stage of development produced a more oxidized and leached soil profile as evidenced by an increase in soil color brightness, kaolinite content, and a decrease in smectite content and soil pH. In addition, pedogenic mixing by biogenic processes probably incorporated the A and E horizons into the overlying loess. A stratigraphic succession of alluvial paleosols may contain a record of regional base level rise and fall. However, an evaluation of eustatic, climatic, and/or tectonic influences on regional base level must first take into account local factors that control flood plain sedimentation and erosion.

• OSTI ID: 5808151
• Report Number(s): CONF-921058-; CODEN: GAAPBC
• Journal Information: Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
MISSISSIPPI RIVER BASIN
DEPOSITION
PLEISTOCENE EPOCH
PALEOCLIMATOLOGY
AGE ESTIMATION
CLIMATIC CHANGE
FLOODS
GEOLOGIC HISTORY
GEOMORPHOLOGY
GLACIERS
SEA LEVEL
SOIL CHEMISTRY
STRATIGRAPHY
CENOZOIC ERA
CHEMISTRY
DISASTERS
GEOLOGIC AGES
GEOLOGY
LEVELS
PALEONTOLOGY
QUATERNARY PERIOD
WATERSHEDS
580000* - Geosciences