Collaborative Research: Stabilized Organic Carbon and Paleoenvironmental Interpretations of Late Quaternary Paleosols

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Collaborative Research: Stabilized Organic Carbon and Paleoenvironmental Interpretations of Late Quaternary PaleosolsMichael Thompson, Iowa State University, EAR-1226949Elmer Bettis III, University of Iowa, EAR-1226412Rolfe Mandel, Kansas University, EAR-1226757Jingdong Mao, Old Dominion University, EAR-1226323ABSTRACTPaleosols are widespread archives of paleoenvironmental information. Many Quaternary paleosols are laterally extensive, readily correlated, and suggestive of periods of regional climatic or geomorphic stability. This grant focuses on organic matter (OM) in paleosols. The objectives of this grant are (1) to identify and rank the importance of mechanisms of OM stabilization at the millennial scale, and (2) to significantly refine paleovegetation reconstructions of midcontinent, Late-Quaternary environments. At five sites in Kansas and Nebraska, OM will be studied in buried paleosols as old as 44.6 ka. These paleosols were chosen (1) to characterize paleosol organic matter in the two most widespread surficial materials in the Midcontinent (alluvium and loess), (2) to compare OM that has witnessed primarily aerated conditions (loess soils) with OM that has been subjected to alternating aerated and saturated condition (alluvial soils); (3) to systematically lengthen the periods in which OM has been buried, giving opportunity for early diagenetic changes to occur; and (4) to capitalize on information available from previous studies.This project will improve understanding of which components of soil organic matter are preserved over millennial time scales and why they are preserved. Such understanding will inform reconstructions of Quaternary paleoenvironments and landscapes that are based on OM-hosted proxies. Of particular interest is the hypothesis that a significant component of stable carbon in paleosols consists of charcoal.By evaluating the significance of charcoal in paleosol OM, the roles that fire can play in carbon storage, landscape evolution, and interpretations of paleoclimate can be elucidated. Because some forms of OM bind together mineral particles, paleosol OM components may regulate the ability of sediments to resist erosion, thus impacting landscape evolution. The research will also help to refine geochemical models that predict the amount of carbon that can be effectively sequestered in soils and provide new insights concerning the long-term stability of terrestrial OM and its impact on global carbon cycles.This project will broaden participation of underrepresented groups in earth sciences through collaboration with colleagues and students at Alabama A&M Univ. AAMU students be invited to join the research team during summer sessions as part of ISU's George Washington Carver Summer Internship program and they will be recruited for graduate studies at Iowa State Univ. and Univ. of Iowa.