Pedogenetic Characteristics and Paleoenvironment Significance of Mesozoic Paleosols in Sichuan Basin
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P532;S151

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National Natural Science Foundation of China (Nos. 41901066,41371225)

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    Abstract:

    [Objective] Detailed inversion of paleoclimates facilitates a better understanding of variation of the climate in the history and provides a basis for predicting future changes triggered by human activities in climate. Paleosol, formed on the Earth's surface during its geological period, is a direct record of the information about the terrestrial environmental conditions when it was formed. Quite a volume of paleosols are found developed within the Mesozoic strata across the Sichuan Basin and they may serve as an important terrestrial archive available for the research on global or regional deep-time paleoclimate.[Method] In this paper, a total of four hundred and thirteen deep-time paleosol profiles were identified in the Mesozoic strata of the Sichuan Basin, southwest China based on the pedogenic characteristics of paleosols. Of the paleosol profiles, observations and analyses were performed for their morphology, micromorphology, mineral composition, particle size composition and geochemical properties, for summarization of their pedogenic characteristics, for researches on their classification, and for discussion of their environmental significance as indicators.[Result] These profiles with distinct pedogenic features, such as presence of root traces and/or animal burrows, accumulation of pedogenic carbonate nodules, vertical variation of color, and development of soil horizons and soil structures, could be sorted into four different types of paleosols (i.e., Paleosol A, Paleosol B, Paleosol C, and Paleosol D). All the paleosol horizons are predominantly composed of quartz and calcite in mineralogy with minor proportions of feldspar, muscovite, illite and/or smectite. And content of the minerals varies with type of the paleosol. The paleosols are obviously lower than their corresponding modern ones in TOC and vary in a similar trend. And moreover, the two are basically consistent in element composition, and do not differ much in geochemical weathering index, leaching index, clayeyness, salinization index, and barium/strontium ratio, which indicate that the paleosols vary in chemical weathering degree with geological period and type of the soil.[Conclusion] According to the standards of the Chinese Soil Taxonomy, the paleosols, observed within the Mesozoic strata of the Sichuan Basin, are analogous to the four orders of modern soil, that is, Primosols, Cambosols, Aridosols, and Argosols, and the proportion of the last is relatively low. The development of the different types of paleosols indicates that the environment of the Sichuan Basin experienced repeated alternations between aridity and humidity during the Mesozoic Era, however, it was mainly under semi-arid and arid weathers.

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LI Jun, HUANG Chengmin, WEN Xingyue, YUE Zhihui. Pedogenetic Characteristics and Paleoenvironment Significance of Mesozoic Paleosols in Sichuan Basin[J]. Acta Pedologica Sinica,2022,59(1):79-91.

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History
  • Received:April 30,2020
  • Revised:October 29,2020
  • Adopted:February 07,2021
  • Online: February 22,2021
  • Published: January 11,2022