The Origin, Provenance, Age and Climatic Links of the Chengdu Clay: A Review
The Chengdu Clay (Chengtu Clay) was named by Thorp and Dye in 1936.The Chengdu Clay is defined as a type of brownish yellow sticky and plastic clay which contains lime concretions overlying the hills and higher terraces in the northwest Sichuan Basin (Szechwan Basin).Thorp and Dye also proposed that the Chengdu Clay is likely a weathered aeolian deposit.The developed Quaternary clayey strata in the northwestern Sichuan Basin can be divided into three units from top to bottom:Chengdu Clay (upper horizon),brown clay (middle horizon) and reticulate-mottled red clay (lower horizon).Within the 70 years after Thorp and Dye,a number of pedologists,geographers and geologists focused on the study of the Chengdu Clay.But,the origin,provenance,age and climatic links of the Chengdu Clay,and the relationship among the Chengdu Clay,loess on the Tibetan Plateau,and loess on the Chinese Loess Plateau are still debatable.The Chengdu Clay as a possible aeolian deposit can provide valuable information about past climate and vegetation,especially information about past wind direction,intensity of atmospheric circulation,source-area aridity and plant cover.In addition,the Chengdu Clay and underlying brown clay and red clay are characterized by overconsolidated,expansive and fissured features.Therefore,the study of these particular clays has theoretical and practical significance.The history of the study for the Chengdu Clay was reviewed in this paper.In addition,a number of research questions for future work have been raised.They involve the following issues:1.further investigation of geomorphological distribution of Chengdu Clay; 2.high-resolution geochronological study of Chengdu Clay and establishment of key profile; 3.origin of brown clay and reticulatemottled red clay; 4.relationship and possible sedimentary hiatus among the Chengdu Clay,brown clay and reticulate-mottled red clay; 5.original relationship among the Chengdu Clay,loess on the eastern Tibetan Plateau,and loess on the Chinese Loess Plateau; 6.the dust provenance and transport mechanism for the Chengdu Clay; 7.connection between the genesis and weathering reworking with the development of overconsolidated,expansive and fissured features for all the clays.
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万方数据
维普
