Tectonic-sedimentary landform classification of 1∶250000 Changde Sheet and its implication for researches on Quaternary geology and environment of Jianghan-Dongting basin

Abstract：The 1∶250000 Changde Sheet strides across Wuling uplift and Jianghan-Dongting basin from west to east, characterized by complicated Quaternary uplift-depression tectonic framework. Based on detailed geological mapping and lots of borehole data, the authors conducted tectonic-sedimentary landform classification and mapping of this sheet according to Quaternary tectonic activity, sedimentation and present elevation and topographic characteristics. Types of tectonic-sedimentary landforms were derived from decomposition of traditional landform types based on Quaternary geological process. Ten types of tectonic-sedimentary landforms were defined, namely, rising-denudation middle-low mountain (Ⅰ), uplift-denudation hilly area (Ⅱ), sedimentary and later uplift-denudation hilly area (Ⅲ), sedimentary and later uplift-denudation hilly plateau (Ⅳ), eluvial-slope wash hilly plateau (Ⅴ), isolated hill (Ⅵ), subsiding-sedimentary and later uplift-denudation hilly plateau (Ⅶ), subsiding-sedimentary and later uplift wave plateau (Ⅷ), stable sedimentary low plateau (Ⅸ) and subsiding-sedimentary low plateau (Ⅹ). A detailed analysis shows that every type of tectonic-sedimentary landform possesses its unique characteristics of elevation, Quaternary uplifting-falling activity, weathering-erosion and sedimentation. Tectonic-sedimentary landform classification and geomorphologic map not only show geographic environments but also provide effective means for direct and visual expression of Quaternary strata, tectonic features and geological-environmental evolution. In addition, these means will promote and deepen researches on Quaternary geology and environment of the Jianghan-Dongting basin.