晚第三纪以前形成古土壤的鉴别、分类及其在古环境研究中的应用

晚第三纪以前形成的古土壤可以揭示地质时期的古环境。辨识古土壤的主要标志包括野外形态特征、微形态特征、地球化学特征等。当前古土壤分类一般基于现代土壤的系统分类体系，即采用诊断层和诊断特征，辅之以古土壤总体的化学性质等指标划分古土壤类型。形成于晚第三纪以前的古土壤可以重建全球范围的古气候变化历史，同时揭示前寒武纪时期古大气O2分压以及后寒武纪时期古大气CO2浓度水平的演化过程；古土壤具有空间和时间等多重信息，能反映流域或区域的古景观、古地貌、古水文特征。但目前缺乏一个广为接受的古土壤分类系统,成岩作用对古土壤特征的影响以及古土壤记录的古环境信息机制与解译等方面也还需要深入探讨。今后必须加强成岩作用对古土壤特性的影响以及现代土壤与其环境的对应关系的研究。

Identification, Classification and Application in Paleoenvironment Research of Pre-Neogene Paleosols

pre-Neogene paleosols can reveal paleoenvironment during geological times. Paleosols were identified by field morphological, micromorphological, geochemical features, and so on. Currently, paleosols are classified based on taxonomic classification of modern soils, i. e, such indices as diagnostic horizons and diagnostic features, in conjunction with bulk chemical properties of paleosols etc. , were employed to sort paleosols. By using paleosols, the history of ancient paleoclimate change might be reconstructed while variation of atmospheric pressure of oxygen and level of carbon dioxide concentration during pre-Cambrian and post-Cambrian periods, as well as paleoecological, paleogeographic features and paleolandscape were rebuilt. However, several problems should be tackled, e.g. establishing an extensively acceptable paleosol classification system, eliminating diagenetic effects on the properties of buried paleosols, and improving the research on the mechanism of paleoclimate information recorded by paleosols and its interpretation, etc. The further studies on diagenetic effects on the properties of buried paleosols and the elaborate relationship between modern soils and pedogenetic environment should be intensified.