Anatomy of a Sub-Cambrian Paleosol in Wisconsin
Anatomy of a Sub-Cambrian Paleosol in Wisconsin: Mass Fluxes of Chemical Weathering and Climatic Conditions in North America during Formation of the Cambrian Great Unconformity L. Gordon Medaris Jr.,1,* Steven G. Driese,2 Gary E. Stinchcomb,3 John H. Fournelle,1 Seungyeol Lee,1,4 Huifang Xu,1,4 Lyndsay DiPietro,2 Phillip Gopon,5 and Esther K. Stewart6 1. Department of Geoscience, University of Wisconsin, Madison, Wisconsin 53706, USA; 2. Department of Geosciences, Terrestrial Paleoclimatology Research Group, Baylor University, Waco, Texas 76798, USA; 3. Department of Geosciences and Watershed Studies Institute, Murray State University, Murray, Kentucky 42071, USA; 4. NASA Astrobiology Institute, University of Wisconsin, Madison, Wisconsin 53706, USA; 5. Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, United Kingdom; 6. Wisconsin Geological and Natural History Survey, Madison, Wisconsin 53705, USA ABSTRACT A paleosol beneath the Upper Cambrian Mount Simon Sandstone in Wisconsin provides an opportunity to evaluate the characteristics of Cambrian weathering in a subtropical climate, having been located at 207S paleolatitude 500 My ago. The 285-cm-thick paleosol resulted from advanced chemical weathering of a gabbroic protolith, recording a total mass loss of 50%. Weathering of hornblende and plagioclase produced a pedogenic assemblage of quartz, chlorite, kaolinite, goethite, and, in the lowest part of the profile, siderite. Despite the paucity of quartz in the protolith and 40% removal of SiO2 from the profile, quartz constitutes 11%–23% of the pedogenic mineral assemblage. Like many other Precambrian and Cambrian paleosols in the Lake Superior region, the paleosol experienced potassium metasomatism, now con- taining 10%–25% mixed-layer illite-vermiculite and 5%–44% potassium feldspar.
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