四川盆地中生代古土壤发生学特征及古环境意义
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P532;S151

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国家自然科学基金项目(41901066,41371225)资助


Pedogenetic Characteristics and Paleoenvironment Significance of Mesozoic Paleosols in Sichuan Basin
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National Natural Science Foundation of China (Nos. 41901066,41371225)

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    摘要:

    古土壤形成于地质历史时期的地球表面,直接记录了其形成时地球陆地表层的环境信息。以四川盆地中生代古土壤为研究对象,通过古土壤的形态与微形态、矿物组成、颗粒组成以及地球化学等成土特征的观察与分析,开展土壤发生学特征概述与分类研究并探讨古土壤指示的环境意义。结果表明:(1)四川盆地中生代古土壤具有生物遗迹、成壤碳酸盐结核、土层颜色变化、土壤发生层次等成土特征。(2)古土壤的矿物组成以石英和方解石为主,含少量长石、蒙脱石和云母类矿物,且不同古土壤类型中矿物含量有差异。(3)古土壤总有机碳含量明显低于现代土壤,但变化趋势与其一致。(4)不同时期不同类型古土壤的化学风化强弱程度不同。古土壤类似于现代的新成土、雏形土、干旱土和淋溶土,其中淋溶土的比例较少。不同类型古土壤的发育表明四川盆地中生代环境整体上在干旱-湿润之间波动变化,但以半干旱、干旱环境为主。

    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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李军,黄成敏,文星跃,岳智慧.四川盆地中生代古土壤发生学特征及古环境意义[J].土壤学报,2022,59(1):79-91. DOI:10.11766/trxb202004300208 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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  • 收稿日期:2020-04-30
  • 最后修改日期:2020-10-29
  • 录用日期:2021-02-07
  • 在线发布日期: 2021-02-22
  • 出版日期: 2022-01-11