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Influences of modern pedogenesis on paleoclimate estimates from Pennsylvanian and Permian paleosols, southeast Ohio, U.S.A.

Sarah J. Kogler and Daniel I. Hembree
Influences of modern pedogenesis on paleoclimate estimates from Pennsylvanian and Permian paleosols, southeast Ohio, U.S.A.
Journal of Sedimentary Research (March 2019) 89 (3): 227-241

Abstract

Paleosols are widely used in paleoclimatic reconstructions. Various proxies based on ratios of major oxides in paleosols have been used to estimate weathering processes, mean annual precipitation (MAP), and mean annual temperature (MAT). The degree of influence that modern weathering and pedogenesis has on the bulk geochemistry of exposed paleosols and the corresponding weathering ratios, however, has not been adequately addressed. In this study, previously analyzed Pennsylvanian and Permian Vertisols and Inceptisols that are actively undergoing pedogenesis were sampled from five roadcuts with known exposure times in southeastern Ohio, USA. Samples were collected at depths of 0, 25, 50, 100, and 150 cm from the outcrop surface. The physical properties of the samples from each depth were described and then analyzed via X-ray fluorescence (XRF) for major-oxide geochemistry. These data were used to calculate molecular weathering ratios, MAP, and MAT at each depth. Results indicate that although physical properties and oxide geochemistry often differ between sampling depths, the differences do not occur in a pattern that supports recent weathering and pedogenesis as a driving factor. Therefore, the decade-level exposure time along these roadcuts effectively limits the extent of pedogenic modification of the paleosols, despite the formation of soils on them. Rather, this study likely captured lateral variations within the paleosols that were the result of small-scale differences in parent material, topography, and biota. Ultimately, for geochemical studies on paleosols in outcrops located on young roadcuts in temperate climates, current sampling techniques appear to be sufficient in mitigating the effects of modern weathering. Recommendations from this study include sampling from 25-50 cm beyond the paleosol surface and taking multiple samples across or into an outcrop to account for lateral variation.


ISSN: 1527-1404
EISSN: 1938-3681
Serial Title: Journal of Sedimentary Research
Serial Volume: 89
Serial Issue: 3
Title: Influences of modern pedogenesis on paleoclimate estimates from Pennsylvanian and Permian paleosols, southeast Ohio, U.S.A.
Affiliation: Baylor University, Department of Geosciences, Waco, TX, United States
Pages: 227-241
Published: 201903
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 58
Accession Number: 2019-032113
Categories: StratigraphyGeochemistry of rocks, soils, and sediments
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., sketch maps
N38°49'60" - N39°10'00", W82°19'60" - W81°45'00"
N39°12'00" - N39°34'60", W82°17'60" - W81°42'00"
Secondary Affiliation: Ohio University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201917
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