第四纪洞庭盆地临澧凹陷构造-沉积特征与环境演化  

Quaternary Tectonic-sedimentary Characteristics and Environmental Evolution of Linli sag,Dongting Basin

作　　者：柏道远[1][2] 刘波 李长安[2] 马铁球 王先辉 彭云益 Chang'an 

机构地区：[1]湖南省地质调查院,湖南,长沙,410011 [2]中国地质大学(武汉)地球科学学院 [3]湖南省常德市地质环境监测站,湖南,常德,415000

出　　处：《山地学报》2010年第6期641-652,共12页Mountain Research

基　　金：1∶25万常德市幅和岳阳市幅区域地质调查(1212010610706);国家自然科学基金项目(40771213)~~

摘　　要：临澧凹陷为第四纪洞庭盆地西部的一个次级构造单元,居于武陵隆起和太阳山隆起之间。通过地表地质调查和钻孔资料对临澧凹陷第四纪构造-沉积特征与环境演化进行了研究。凹陷呈SN向,全长约55km,宽5～10km。受SN向雷公庙断裂和渐水断裂控制,凹陷中央形成断槽。凹陷分为南、北两段,其间前第四纪基底上凸。在凹陷北段,中央断槽内为最厚达270m的中更新世洞庭湖组,其主体为含砾粘土与粘土互层,顶部为粘土、含粉砂质粘土;断槽东面自西往东依次为中更新世中期白沙井组(含粉砂质)湖相粘土和更新世残坡积层;断槽西面依次为白沙井组(含粉砂质)湖相粘土和中更新世早期新开铺组砾石层,后者组成基座阶地。在凹陷南段,中央断槽内中更新世早期-中期沉积厚100m左右,顶部为湖相粘土,往下为冲积层;断槽东面发育白沙井组冲积砂砾层;断槽西面依次发育白沙井组和新开铺组,前者自下而上分别为冲积含砾砂层和湖相粘土,后者为冲积砂砾层并组成堆积阶地。根据地貌、沉积和断裂特征,重塑临澧凹陷构造活动与环境演化过程:中更新世早期渐水由西部进入临澧凹陷区后向南汇入沅水,于凹陷南段形成冲积层;同时来自西面山地的次级水系于凹陷西缘形成砾石层。中更新世中期受两侧正断裂控制中央断槽开始形成并接受沉积,其中北段断槽形成相对封闭的湖泊,南段断槽为河流环境;与此同时,断槽西面相对抬升并遭受剥蚀,稍后南段尚形成白沙井组冲积层。中更新世中后期临澧凹陷南、北段均产生扩张并处于湖泊环境,于中央断槽和两侧边缘形成泥质沉积。中更新世晚期构造反转,临澧凹陷整体抬升、遭受剥蚀且地表粘土发生网纹化,同时具有自西向东的掀斜,造成凹陷西侧水系更为发育。晚更新世因切割和剥蚀而形成丘岗地貌,并形成改造型或坡积型的褐色铁Linli sag is western one of the secondary tectonic units of the Dongting basin,and is located between Wuling uplift and Taiyangshan uplift. Detailed geologic mapping and bore data was taken to study on the Quaternary tectonic and sedimentary characteristics and environmental evolution of Linli sag. The sag trend north with about 55 km length and 5-10 km width. Controlled by SN-trending Leigongmiao fault and Jianshui fault,there occurred faulted trough at center of the sag. The sag can be divided into two segment from south to north with pre-Quaternary basement uplifting at center. At the north segment of the sag,in the faulted trough there occurred Middle Pleistocene Dongtinghu Formation with maximun thickness of 270 m that is mainly composed of gravel-bearing clay and clay with the top part composed of clay and silt-bearing clay; to east of the trough there exis from west to east silt-bearing clay and clay of middle Middle Pleistocene Baishajin Formation and Pleistocene residual soil; to west of the trough there exist from east to west silt-bearing clay and clay of Baishajin Formation and gravels of early Middle Pleistocene Xinkaipu Formation making up base terrace. At the south segment of the sag,in the faulted trough there occurred early-middle Middle Pleistocene about 100 m-thick deposits composed of top lacustrine clay and low alluvial deposits; to east of the trough there exis alluvial deposits of Baishajin Formation; to west of the trough there exist from east to west alluvial gravel-bearing sands and lacustrine clay of Baishajin Formation and alluvial sand-gravel layers of Xinkaipu Formation making up terrace. Based on geomorphologic,sedimentary and fault characteristics,evolution of the Quaternary tectonic and environment is defined. Jianshui river entered into Linli sag and flowed south into Yuanshui river,while alluvial deposits were formed at south segment of the sag during early Middle Pleistocenc; in the same time,secondary rivers from west mounts formed gravels in the west periphery of the sag. Con

关 键 词：第四纪构造 洞庭盆地 凹陷构造 沉积特征 环境演化过程 中更新世早期 湖相粘土 冲积层 沙井 断裂控制 中更新世晚期 砂砾层 砾石层 粉砂 发育 次级构造单元 剥蚀 北段 钻孔资料 走滑拉分 

分 类 号：P9[天文地球—自然地理学]