Modern,Sangamon and Yarmouth soil development in loess of unglaciated southwestern Illinois |
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| Institution: | 1. GeoQuest Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, 2522 NSW, Australia;2. Desert Research Institute, Nevada System of Higher Education, Reno, NV 89512, USA;1. Faculty of Natural Resources & Marine Sciences, Tarbiat Modares University, 46417-76489 Noor, Mazandaran, Iran;2. Research Department, The Morton Arboretum, 4100 Illinois Route 53, Lisle, IL 60532-1293, USA;3. Department of Forestry, University of Natural Resources and Agriculture Sciences of Sari, Mazandaran, Iran;4. Department of Soil Sciences, Shahrekord University, Shahrekord, Iran;1. Department of Geography, Northern Illinois University, DeKalb, IL 60115, USA;2. Illinois State Geological Survey, Institute of Natural Resource Sustainability, University of Illinois at Urbana-Champaign, 615 E. Peabody Dr., Champaign, IL 61820, USA;1. Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan;2. Graduate School of Global Environmental Studies, Kyoto University, Kyoto 606-8501, Japan;3. College of Agriculture, Sokoine University of Agriculture, Morogoro, Tanzania;1. Department of Biological Sciences, University of Illinois at Chicago, 845 W. Taylor St. M/C 066, Chicago, IL 60607, USA;2. Biosciences Division, Argonne National Laboratory, 9700 S. Cass Ave., Argonne, IL 60439, USA;3. Illinois State Geological Survey, Prairie Research Institute, University of Illinois, 615 E. Peabody Dr., Champaign, IL 61820, USA |
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| Abstract: | The Thebes Section in unglaciated southwestern Illinois contains a well preserved ～500 kyr loess–paleosol sequence with four loesses and three interglacial soils. Various magnetic, mineralogical, and elemental properties were analyzed and compared over the thickness of soil sola. These proxies for soil development intensity have the following trend: Yarmouth Geosol>Sangamon Geosol>modern soil. Quartz/plagioclase, Zr/Sr, and TiO2/Na2O ratios were most sensitive to weathering. Frequency dependent magnetic susceptibility and anhysteretic remanent magnetization, greatest in A horizons, also correspond well with soil development intensity. Neoformed mixed-layered kaolinite/expandables, suggestive of a warm/humid climate, were detected in the Sangamon and Yarmouth soil sola. Clay illuviation in soils was among the least sensitive indicators of soil development. Differences in properties among interglacial soils are interpreted to primarily reflect soil development duration, with climatic effects being secondary. Assuming logarithmic decreases in weathering rates, the observed weathering in the Sangamon Geosol is consistent with 50 kyr of interglacial weathering (Oxygen Isotope Stage 5) compared to 10 kyr for the modern soil (Oxygen Isotope Stage 1). We propose that the Yarmouth Geosol in the central Midwest formed over 180 kyr of interglacial weathering (including oxygen isotope stages 7, 9, and 11). |
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