洞庭湖赤山凸起第四纪构造沉积演变特性

Quaternary tectono-sedimentary evolution of Chishan Uplift in the Dongting Lake

  • 摘要: 第四纪以来,洞庭湖赤山凸起构造沉积演变活跃,致使其第四纪地层沉积时代、成因及构造活动较为复杂,而赤山凸起作为洞庭湖内部重要的地质构造单元,研究其第四纪构造沉积演变特性对探索洞庭湖第四纪历史演变有着重要的地质意义。本文从地质构造、地层岩性、古气候、文化遗址等多角度入手,对赤山凸起第四纪构造沉积演变特性进行深入探究。研究结果表明:赤山凸起第四纪更新统沉积有早更新世汨罗组、中更新世新开铺组和白沙井组地层,并自下而上形成河湖相沉积镶嵌阶地。赤山凸起早更新世晚期构造活动表现为先凹陷后稳定,中更新世早期—中期末表现为稳定—凹陷—稳定—凸起—稳定。中更新世晚期初,赤山凸起基岩面海拔0 m及以上区域已凸起成陆,并开始出现人类活动,同时在当时第四系顶部遗留下旧石器遗址。中更新世晚期至全新世初赤山凸起均处于剥蚀状态,并在其地势较低区域地表下沉积风成堆积层。

     

    Abstract: Tectonic activities were reactivated since Pleistocene at the Chishan Uplift of the Dongting Lake where complicated geological phenomena are observed. As an important geological unit in the Dongting Lake, the study of the uplift and the evolutionary characteristics of the Quaternary structures and depositional systems is of great significance to the exploration of the Quaternary history of the lake. Thus, a thorough study from the perspectives of geological structure, stratigraphic framework, lithology and paleoclimate as well as cultural relics, is made by the authors in this paper. Results show that: In the late Early Pleistocene, the structural activity of Chishan uplift was first depressed and then stable, and in the early to middle Pleistocene, it was stable - depressed-stable-raised-stable. In the beginning of late Middle Pleistocene, the area with the elevation of 0 m and above of the bedrock surface of Chishan uplift had been uplifted and formed land, and human activities began to appear. At the same time, paleolithic sites were left on the top of the Quaternary strata at that time. From late Middle Pleistocene to early Holocene, the Chishan Uplift was denuded, and the aeolian deposits were deposited in the lower area of Chishan uplift.

     

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