江汉—洞庭地区与黄广—九江地区更新统划分与对比

为进一步厘清长江中游江汉—洞庭地区与黄广—九江地区更新统划分与对比,在区域地质调查基础上,识别出区内早更新世砾石层与上覆网纹红土之间的不整合关系,辅以年代学研究,开展了长江中游江汉—洞庭地区与黄广—九江地区第四系研究,建立了区域地层划分与对比格架。研究表明: 白沙井砾石层、阳逻砾石层、宜昌砾石层、九江砾石层等是区内短程河流的冲洪积相沉积,时代为早更新世晚期(Qp₁),而上覆网纹红土则形成于中更新世(Qp₂),二者之间为不整合接触,并以此为基础构建了区内第四纪更新世地层格架; 白沙井砾石层、阳逻砾石层、宜昌砾石层、九江砾石层与上覆网纹红土所代表的水动力条件和沉积环境的重大调整是长江三峡续接贯通的环境响应,暗示了长江上游“川峡二江”续接贯通的时限为早—中更新世之交。

Division and comparison of Pleistocene in Jianghan-Dongting area and Huangguang-Jiujiang area

In order to further clarify the division and comparison of Pleistocene of Jianghan-Dongting and Huangguang-Jiujiang areas in the middle reaches of Yangtze River, based on the regional geological survey, the unconformity relationship between the Early Pleistocene gravel layer and the overlying latticed laterite was identified in this paper. And the Quaternary System of this area has been studied, with supplementary of chronology study. Besides, reginal sequence division and comparative framework were established. The results show that gravel layers, such as Baishajing, Yangluo, Yichang and Jiujiang, were the pluvial facies sediments of Yangtze River, and epoch was late Early Pleistocene (Qp₁). The overlying reticulate red clay was formed in Middle Pleistocene (Qp₂), and the contact relationship between these two layers was unconformity. The stratigraphic framework of Pleistocene Series in this area was established based on the research results above. The major adjustment of hydrodynamic conditions and sedimentary environment represented by gravel layers, such as Baishajing, Yangluo, Yichang and Jiujiang, and the overlying reticulate red clay were the environmental response of the continuous connection of Three Gorges of Yangtze River. It also suggested that the continuous connection of Three Gorges of Yangtze River occurred in the Early to Middle Pleistocene.