| 库车坳陷西段盐构造二维平衡恢复与复原构造剖面分析 |
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| 引用本文： | 高麟,汪新,饶刚.库车坳陷西段盐构造二维平衡恢复与复原构造剖面分析[J].地质学报,2020,94(6):1727-1739. |
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| 作者姓名： | 高麟 汪新 饶刚 |
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| 作者单位： | 浙江大学地球科学学院，杭州，310027 |
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| 基金项目： | 本文为国家科技重大专项（2017ZX05008001）资助的成果。 |
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| 摘 要： | 天山南麓库车坳陷西部沉积古近系膏盐岩,盐层下伏中生界发现万亿立方米储量天然气田,是我国西气东输重要气源。库车坳陷盐下是油气勘探关注目标,目前研究认识不能满足勘探需求,尤其是盐构造形成机制存在争议,盐构造平衡恢复是研究难点。本文应用二维构造平衡剖面技术,综合地震剖面、钻井和地表地质资料,选取库车坳陷西段四条剖面,通过StructureSolver公司开发的构造恢复软件(简称SS),开展平衡恢复工作,分层恢复盐上层、膏盐层、盐下层,复原挤压变形前地震剖面。研究结果揭示库车坳陷西段发育二期盐构造:渐新世-中新世发育刺穿型盐丘,上新世-第四纪发育挤压型盐构造。挤压作用下早期盐丘演变为盐席、盐墙,盐上层发育盐逆冲断层和盐背斜,盐下发育叠瓦状逆冲断层和挤压构造楔。库车坳陷西段盐层上覆冲积扇沉积(重力)差异负载是发育盐丘的原因,盐丘分布于山前冲积扇前端和却勒冲积扇南侧。库车坳陷盐下发育逆冲构造楔,应用临界楔理论研究构造楔顶面坡度与底部滑脱层角度变化,盐下构造楔顶面坡度突变,指示底部滑脱层角度发生变化,推断古生代基底正断层卷入逆冲构造楔。
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| 关 键 词： | 库车坳陷 盐构造 二维平衡恢复 构造楔 基底断裂 |
| 收稿时间： | 2020/3/30 0:00:00 |
| 修稿时间： | 2020/5/5 0:00:00 |
Two-dimensional balanced restoration of salt structures and analysis of restored cross sections in the western Kuqa depression |
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| GAO Lin,WANG Xin,RAO Gang.Two-dimensional balanced restoration of salt structures and analysis of restored cross sections in the western Kuqa depression[J].Acta Geologica Sinica,2020,94(6):1727-1739. |
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| Authors: | GAO Lin WANG Xin RAO Gang |
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| Institution: | School of Earth Sciences, Zhejiang University, Hangzhou, 310027 |
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| Abstract: | The Paleogene gypsum- salt rocks were deposited in the western Kuqa depression at the southern piedmont of Tian Shan. Trillions of cubic meters of nature gas fields were discovered within the Mesozoic strata below the gypsum- salt layer, an important gas source for the west east gas transmission in China. The sub- salt in Kuqa depression is a target for oil and gas exploration. At present insufficient understanding of the formation mechanism of the salt structure, which requires restoration of salt structure balance, hinders gas exploration. We have, in this paper, by integrating seismic, drilling and surface geological data from four selected sections of the western Kuqa depression, undertaken tectonic balance restoration using the StructureSolverTM (SS) restoration software developed by StructureSolver Company. We have restored the seismic image before compression deformation of the supra- salt layer, salt layer, and sub- salt layer to rebuild the pattern of the seismic profiles before compression deformation. The results reveal that two stages of salt structures were developed in the western Kuqa depression: piercing salt dome developed in the Oligocene to Miocene, and extruded salt structures developed in the Pliocene to Quaternary. Under compaction, the salt dome developed in the early stage evolved into salt sheets and salt walls, thrust faults and salt anticlines developed in the supra- salt layer, and imbricated thrust faults and critical- taper wedge developed in the sub- salt layer. The differential loading of the overlying salt layer (gravity) was the reason for the development of the salt dome in the western Kuqa depression. The salt domes in the western Kuqa depression are distributed in front of the piedmont alluvial fan and on both sides of Quele alluvial fan. Critical taper wedge developed in the sub- salt layer in western Kuqa depression. The critical taper wedge theory is used to study the relationship between the slope of the top surface of the wedge and the angle of the bottom detachment layer. The slope of the top surface changes abruptly signifying variation in the angle of the detachment layer, thus indicating that the Paleozoic basement normal fault was involved in the wedge. |
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| Keywords: | Kuqa depression salt tectonics two- dimensional balanced restoration critical taper wedge basal fractures |
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