Quaternary tectonic and sedimentary characteristics and geological evolution of the Huarong uplift and its adjacent areas

Abstract：Quaternary Huarong uplift is located at the center of Jianghan-Dongting basin. Detailed geological mapping and bore data analysis were conducted to investigate Quaternary tectonic and sedimentary characteristics and geological evolution. EW-trending Huarong uplift is adjacent to north Jianghan basin, south Anxiang sag and Yuanjiang sag of Dongting basin. The framework of the uplift is controlled by several surrounding Quaternary normal faults such as EW-trending Shishou fault, NW-trending Nanxian-Huangshantou fault and NNE-trending Zhuanqiao fault. There generally occurred alluvial or lacustrine deposits in every period of Quaternary in the peripheral sags. Late Early Pleistocene-Holocene deposits are located in the inner lower areas of the uplift and on the edge of the mountainous area, and pre-Quaternary rocks or residual deposits are distributed in the other areas of the uplift. On the basis of studying landforms, boundary faults, distribution of Quaternary deposits and pre-Quaternary rocks, the authors recovered the Quaternary evolution of Huarong uplift and adjacent areas in such aspects as rising and subsidence, sedimentation and denudation. There had occurred original hypsographic differentiation inside Huarong uplift in springtime of Quaternary before denudation. During early Early Pleistocene the normal faults around the uplift moved. At the same time, Jianghan basin, Anxiang sag and Yuanjiang sag subsided and received deposits and Huarong uplift was denuded. During the late Early Pleistocene—middle Middle Pleistocene period the normal faults continued to move, Huarong uplift and peripheral sags subsided, and the uplift rose relative to the sags. At the same time there occurred deposits in low areas of Huarong uplift and its peripheral sags, and there existed tectonic rising and denudation at the end of Early pleistocene. During late Midle Pleistocene Huarong uplift and peripheral sags rose and were denuded, forming vermicular red earth. There was a stable period in late Middle pleistocene when fluvial and lake-frontal deposits were formed on the edge of main Huarong-Zhuanqiao body of the uplift. Alluvial and lacustrine deposits were formed on the edge of the uplift and in the peripheral plain during Late Pleistocene under the relatively stable condition. At the end of Late Pleistoncene regional sea-level was lowered, causing the denudation of Huarong uplift and its peripheral areas. There occurred lacustrine-alluvial deposits in low areas of Huarong uplift and peripheral sags in Holocene due to the rising of regional river and lake level. Controlled by early high topography, the main body of Huarong uplift and parts of south Nanshan sub-uplift and Tanshan sub-uplift were weathered and denuded throughout Quaternary, resulting in the formation of large-sizes residual soil in some areas. Controlled by overall subsidence of Jianghan-Dongting basin, Huarong uplift subsided markedly in Quaternary as a whole.