Chronostratigraphic and paleoclimatic data for Quaternary loessial and fluvial deposits in the Mississippi River Valley of Arkansas and Tennessee

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5932331

Markewich, H W ^[1]; Millard, Jr, H T ^[2]; Pavich, M J ^[3]; Rodbell, D T ^[4]; Rich, F J ^[5]; Rutledge, E M ^[6]; Ward, L ^[7]; Van Valkenberg, S ^[3]; Wysocki, D ^[8]

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1. Geological Survey, Atlanta, GA (United States)
2. Geological Survey, Denver, CO (United States)
3. Geological Survey, Reston, VA (United States)
4. Geological Survey, Golden, CO (United States)
5. Georgia Southern Univ., Statesboro, GA (United States)
6. Univ. of Arkansas, Fayetteville, AR (United States)
7. Dept. of Agriculture, Little Rock, AR (United States). Soil Conservation Service
8. Dept. of Agriculture, Lincoln, NE (United States). Soil Conservation Service

Ongoing investigations into Quaternary paleoclimates of the Mississippi River Valley in eastern Arkansas and western Tennessee include age estimations using [sup 14]C, [sup 10]Be, thermoluminescent (TL), and optically stimulated luminescent (OSL) analyses; compositional studies using petrographic and diffractometer analyses; pedological analyses with complete characterization studies; and magnetic susceptibility measurements with laboratory analyses to investigate the source of the magnetism. Preliminary data on composition of the < 63-micron fraction, thickness, and age of the loesses and associated paleosols are available from selected stratigraphic sections that are being described and sampled in detail. These data suggest the following: (1) overall thickness of loess, as well as thickness of each loess sheet, decreases by one-half to two-thirds within the 96-km distance from the south end of Crowleys Ridge near Helena, AR northward to Forest City, AR and Memphis, TN; (2) near Helena, loess thicknesses are 25 to 30 m, 7 m, 6 m, and 6 m for the Peoria, Roxana, Loveland, and Crowleys Ridge respectively; (3) the depth of weathering in the Peoria ranges from 4.5 to 8.5 m near Helena, depending on slope position; (4) at the south end of Crowleys Ridge, near Helena, the Roxana has two associated paleosols and an intervening layer of weathered parent material; (5) isotopic data suggest that (a) loess deposition took place between 4,500 ka and 10 ka and that (b) each younger disconformity represents less time than the one before; (6) the predominantly illite and illite/smectite mineralogy of the paleosols, even that of the Sangamon soil, suggests minimal weathering of labile loessial minerals prior to pedogenic development; (7) pollen data indicate that by 10 ka this part of the valley had vegetation indicative of a cool temperate climate, with minimal cypress and no boreal components.

• OSTI ID: 5932331
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ARKANSAS
CENOZOIC ERA
CHEMISTRY
DEPOSITION
DEVELOPED COUNTRIES
DIMENSIONS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOLOGIC STRATA
GEOLOGIC STRUCTURES
GEOLOGY
MAGNETISM
NORTH AMERICA
PALEOCLIMATOLOGY
PALEOMAGNETISM
PALEONTOLOGY
QUATERNARY PERIOD
SEDIMENTARY BASINS
STRATIGRAPHY
TENNESSEE
THICKNESS
USA
WEATHERING