1∶25万常德市幅区域地质调查主要进展及成果

Main Progress and Achievements in Regional Geological Survey of 1:250000 Changde Sheet

1∶25万常德市幅区域地质调查项目对洞庭盆地第四纪地质特征及演化进行了重点研究,取得以下主要进展及成果:1厘定了洞庭盆地及周缘隆-凹构造格局,并分别对洞庭盆地各次级构造单元及其周缘地区的第四纪地质特征及演化进行了详细解剖。2通过孢粉组合和沉积物地球化学特征重塑了第四纪气候演化过程;通过重矿物组合探讨了洞庭盆地南部河湖变迁以及构造沉降过程。3确定洞庭盆地早更新世—中更新世中期处于断陷阶段、中更新世晚期以来处于拗陷阶段,并详细查明了各阶段构造活动特征,提出了新的构造活动动力机制模式。4新提出"构造-沉积地貌类型"的概念,对图区进行了构造-沉积地貌类型的划分。

The regional geological survey project of 1 ： 250 000 Changde sheet have studied the Quaternary geological and environmental characteristics and evolution of the Dongting basin, and achieved progress as follows ： ①We found out the Quaternary uplift-depression tectonic framework of the Dongting basin and peripheral area, and amply studied the Quaternary tectonic and sedimentary characteristics and environmental evolution of every secondary tectonic unit of the Dongting basin and its periphery area. ②We revealed the climatic evolution of the Dongting basin through pollen assemblages and geochemical characteristics of sediments, and discussed the evolutions of the sedimentary environment and tectonic subsidence of the southern Dongting basin through heavy minerals. ③We ascertained the tectonic movement characteristics of the basin that the Dongting basin was a rift basin during Early Pleistocene-middle of Middle Pleistocene, and entered into a depression phase since late Middle Pleistocene, and advanced geodynamic mechanism model of every tectonic period. ④We brought forward the concept of tectonic-sedimentary landforms, and defined tectonic-sedimentary landform types in the sheet.