Formation and Evolution of a Paleosol across the Lower Silurian-Lower Permian Boundary in Zunyi District, Northern Guizhou, China and Its Paleoenvironment and Paleoclimate Implications
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This work was supported by 12th Five-Year Plan Project of State Key Laboratory Of Ore Deposit Geochemistry Chinese Academy of Sciences (SKLODG-ZY125-08), funds from State Key Laboratory of Palaeobiology and Stratigraphy Chinese Academy of Sciences and Chinese National Program on Key Basic Research and Development (2007CB411408). We thank prof. WANG Shijie (Institute of Geochemistry, CAS) for giving good advices before writing this paper, and also thank HU Xiaoyan for Major elements, HU Jing for Trace elements and GONG Guohong for XRD analysis.

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    Abstract:

    This paper presents a set of bulk geochemical and mineralogical data from a paleoweathering profile located in Zunyi District, Northern Guizhou, China. It was formed at the top of the Hanjiadian Formation of the Lower Silurian. A truncated, argillic, gleyed, kryptic paleospodosol is recognized in the paleoweathering profile. Ratios of immobile elements (Ti/Zr, Ti/Al) and their binary (e.g., Nb vs. Zr/TiO2 and Th/Sc vs. Zr/Sc), triangular diagrams (La-Th-Sc, Th-Sc-Zr/10, Zr-Cr-Ga) reflect that the Gaojiayan paleosol is the product of in-situ weathering of gray-green silty mudstone of the underlying Hanjiadian Formation. Mass balance calculations indicate K enrichment and Na enrichment in the upper and lower portions of paleosol, respectively. These findings both are the results of transgression, which brings substantial concentrations of such elements as K, Na, and Sr. In particular, K enrichment is achieved by the illitization of kaolinite. The biological processes of terrestrial vascular plants also enhance K concentration, especially at the top of the paleosol. Na enrichment is a consequence of albitization and/or adsorption by clay minerals through cation exchange. The mass distributions and relative mass changes of rare earth elements (REEs) in the studied profile display characteristics of vertical zonation. Three peaks in total REEs content are observed, indicating two paleoclimatic or paleoenvironmental changes. Mineralogical characteristics indicate that the paleoclimate changed first from warm and humid to cold and dry and later, to dry and lightly warmer. The corresponding soil environment varies from weakly acidic to strongly alkaline and later, to weakly acidic. Mass translocation characteristics of REEs and several transition metals suggest that the Gaojiayan paleosol may have undergone top erosion.

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XIONG Xiaohui, XIAO Jiafei, HU Ruizhong, WANG Jian, WANG Yi, WANG Xinsong, DENG Qi.2015. Formation and Evolution of a Paleosol across the Lower Silurian-Lower Permian Boundary in Zunyi District, Northern Guizhou, China and Its Paleoenvironment and Paleoclimate Implications[J]. Acta Geologica Sinica(),89(6):2012-2029

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History
  • Received:May 10,2014
  • Revised:December 13,2014
  • Adopted:
  • Online: December 16,2015
  • Published: