川西坳陷中段盆山过渡带构造变形特征及其演化

Structure deformation and evolution of basin-mountain transition zone in middle part of western Sichuan Depression

郭卫星¹ 李书兵¹ 刘树根² 罗啸泉¹ 王睿婧²

中国石化西南油气分公司勘探开发研究院，四川 成都 610081 成都理工大学，四川 成都 610059

Research Institute of Exploration and Development, Southwest Oil and Gas Company, SINOPEC, Chengdu 610081, China Chengdu University of Technology, Chengdu 610059, China

川西坳陷中段盆山过渡带地震资料品质较差，构造解释存在多解性。前人多采用前展式逆冲叠瓦构造模型进行解释，文中依据露头、钻井和地震资料分析认为，分层变形构造模型更加合理。盆山过渡带以安县—灌县断层和关口断层为界，可分为叠瓦构造带、分层变形带和山前单斜带。垂向构造以须家河组3段和中、下三叠统为界，分为浅层、中层和深层3个层次，浅层和中层总体呈叠瓦构造，深层构造变形弱。以绵竹为界，研究区分为北东段和南西段，北东段构造倾角大、垂向位移明显，南西段构造倾角小、水平位移大。构造演化分析表明，印支晚期以安县—灌县断层活动为代表，推覆构造活动强烈并有较大的水平收缩变形量；燕山早期构造相对平静；燕山中—晚期和喜马拉雅期关口断层发育，水平收缩变形量相对小，而基底隆升明显。

Quality of seismic data for basin-mountain transition zone in middle part of western Sichuan Depression is poor. So, there is ambiguity in structure interpretation. Basement-involved in-sequence imbricate structure model is adopted to interpret structure by predecessors. Based on outcrop, drilling and seismic data, this paper considers that the stratified deformation structure is more reasonable. Bounded by Anxian-Guanxian Fault and Guankou Fault, basin-mountain transition zone can be divided into imbricate structure belt, stratified deformation belt and mountain front monocline belt. Bounded by the 3rd Member of Xujiahe Formation and Middle-Low Triassic, vertical structure can be divided into shallow layer, middle layer and deep layer. Shallow layer and middle layer structures are imbricate on the whole and the deformation of deep layer structure is weak. Basin-mountain transition zone in study area is divided into northeastern section and southwestern section bounded by Mianzhu. Northeastern section has high-angle structure and its vertical displacement is obvious. Southwestern section has low-angle structure and horizontal displacement is large. Analysis of structure evolution shows that the activity of Anxian-Guanxian Fault is representative in Late Indo-Chinese epoch, the activity of nappe structure is strong and horizontal contraction is large. Structure deformation is weak in early Yanshanian epoch. In Mid-Late Yanshanian and Himalayan epoch, Guankou Fault developed and horizontal contraction was small, which associated with obvious basement uplift.

10.6056/dkyqt201206002