TY - JOUR
T1 - Modern, Sangamon and Yarmouth soil development in loess of unglaciated southwestern Illinois
AU - Grimley, David A.
AU - Follmer, Leon R.
AU - Hughes, Randall E.
AU - Solheid, Peter A.
N1 - Funding Information:
The manuscript benefited greatly from review comments of Peter Birkeland, Peter Clark, and Joe Mason. We gratefully acknowledge Dan Muhs (US Geological Survey) for helping to provide the geochemical data and for many constructive comments. The authors also thank B. Brandon Curry (ISGS) and John E. Werner (University of Illinois) for their comments and suggestions. W. Hilton Johnson helped in the early stages of this study, both conceptually and with field work, as the senior author's dissertation advisor. Subir K. Banerjee (University of Minnesota Institute for Rock Magnetism) supported use of equipment in this facility for ARM and X fd measurements. Steven Altaner (University of Illinois) provided use of an X-ray diffractometer for silt mineralogy and provided some advice with geochemical interpretations. Gary Pulley (Illinois Department of Transportation, Carbondale, IL) provided the Thebes Core. This research was partially funded by Geological Society of America and Sigma Xi dissertation research grants for field expenses.
PY - 2003/2
Y1 - 2003/2
N2 - 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).
AB - 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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U2 - 10.1016/S0277-3791(02)00039-2
DO - 10.1016/S0277-3791(02)00039-2
M3 - Article
AN - SCOPUS:0037319385
SN - 0277-3791
VL - 22
SP - 225
EP - 244
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
IS - 2-4
ER -