摘要
湘中盆地中部的大乘山-龙山EW向隆起将湘中盆地分为涟源和邵阳两个次级凹陷。湘中盆地西部上古生界盖层中主体构造为NE—NNE向褶皱和逆断裂,前人认为其变形与向北西的逆冲推覆有关。本文对湘中盆地西部进行了多条构造剖面调查,结果表明:涟源凹陷西部上古生界褶皱轴面大多直立、部分斜歪;走向逆断裂及斜歪褶皱轴面大多倾向NW,少量倾向SE。大乘山背斜为一轴面倾向NWW的倒转背斜,背斜核部及两翼发育大量以NWW倾向为主的逆断裂,背斜内长安组劈理均倾向NWW。邵阳凹陷西部上古生界中走向逆断裂和倒转与斜歪褶皱轴面总体倾向NWW,局部反冲构造带断裂倾向SEE。湘中盆地盖层变形主要受控于盖层底部不整合界面及石炭纪测水组煤系地层的滑脱,部分断裂切入加里东褶皱基底。上述各次级构造单元变形特征表明湘中盆地西部逆冲推覆的总体方向为SE,而不是前人所认为的NW。研究表明湘中盆地NE—NNE向褶皱和逆断裂形成于中三叠世晚期的印支运动和中侏罗世晚期的早燕山运动。分析认为湘中盆地西部向SE逆冲,与雪峰造山带东缘向SE逆冲及城步-新化岩石圈断裂向NW俯冲有关。
The Xiangzhong basin is divided into Lianyuan depression and Shaoyang depression by the EW- trending Dachengshan-Longshan uplift. In the upper Paleozoic of the western Xiangzhong basin, there occur NE-to NNE-trending folds and thrust faults which have been considered to be related to the NW- thrust. This study carried out investigation over several structural sections in the western Xiangzhong basin. The results reveal the deformation characteristics. The most many axial planes of the Upper Paleozoic folds in the western Lianyuan depression are vertical with some inclined and the most axial planes of the trending thrust faults and inclined folds dip northwest with minor dipping southeast. The Dachengshan anticline is an overturned fold with an NWW-dipping axial plane and a number of NWW- dipping thrust faults are developed within core section and two wings of the anticline with the cleavages occurring in the Chang^an Formation. In the western Shaoyang depression, the thrust faults and the axial planes of inclined and overturned folds in the Upper Paleozoic dip NWW, with partial folds dipping SEE. The deformations of the cover in the Xiangzhong basin are controlled mainly by the detachment of the bottom unconformity surface and of the coal bed of the Ceshui Formation, and some faults incise through the Caledonian folded basement. Deformation characteristics of the secondary tectonic units indicate that the thrusting directions of western Xiangzhong basin are SE and not NW but not the NW direction proposed by previous studies. Studies show that the NE-to NNE-trending folds and thrust faults in the Xiangzhong basin were formed in late Middle Triassic Indosinian Movement and late Middle Jurassic Early Yanshanian Movement. Our study suggests that the SE-thrusting of the western Xiangzhong basin is related with the SE-thrusting of east periphery of the Xuefeng orogenic belt, and with the NW-subduction of Chengbu-Xinhua lithospheric fault.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2013年第12期1791-1802,共12页
Acta Geologica Sinica
基金
中国地质调查局"湖南1:25万武冈市和永州市幅区调修测"项目(编号1212011120793)
"中国地质构造区划综合研究与区域地质志修编"项目(编号1212010811032)
中上扬子及邻区重点盆地地质地球物理综合调查(编号1212011120967)共同资助的成果
关键词
褶皱
断裂
逆冲方向
成因机制
湘中盆地西部
fold
fault
thrusting direction
tectonic mechanisms
western Xiangzhong Basin