塔西南坳陷西昆仑山前冲断带的收缩构造变形模式
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摘要
通过对地面地质、地震和连续电磁剖面资料的综合分析研究,提出"分层收缩、垂向叠置"的"非俯冲"型收缩构造解释模型,即由于上白垩统—古近系膏盐岩软弱岩层的分隔以及地层垂向能干性的差异,导致浅、中、深层分别发育不同的收缩变形样式,而不存在区域性的具有大位移量的拆离断层在水平方向叠置。浅层盐岩层之上的新生界能干岩层以滑脱褶皱变形为主,表现为近直立对称的长轴背斜与造山带平行排列;中层盐下层中生界及深层盆地基底岩系以韧性收缩变形为主,发育向西昆仑山倾斜的高角度基底卷入逆冲断层。断层上盘形成冲断隆起,下盘发育一系列同向倾斜的次级分支断层,构成楔状叠瓦扇,终止于反冲断层下盘的膏盐岩中。基底卷入的高角度逆冲断层可能利用了侏罗纪、白垩纪的先存正断层发生反转,并控制了下盘局部构造变形。西昆仑山隆升引起的垂直剪切作用可能是山前冲断带发育高角度逆冲断层及先存正断层反转的原因。
Through comprehensive analysis of the surface geology,seismic profile and continuous electromagnetic profile(CEMP) data in west Kunlun piedmont thrust belt in southwestern depression of Tarim basin,a non subduction-like contraction structure interpretation model with the layering contraction and vertically stacking style is proposed,which means that different styles of structural contraction and deformation occur in shallow and mid-deep layers owing to the detachments caused by the salt-gypsum rocks of Upper Cretaceous-Paleocene and competent strata's distribution in vertical direction.It seems that the detachment fault could not be stacked with another regional detachment fault whose horizontal displacement is great.The Cenozoic competent strata above the shallow salt layer are dominated by decollement fold deformation,which appears near perpendicular and symmetrical long-axis anticline,being parallel to the orogenic belt.The Mesozoic of middle subsalt layer and the deep basement rock formation in this basin are dominated by tenacious contraction deformation,and a series of basement-involved thrust faults with high-angle dipping to West Kunlun are developed.Thrust uplift may be formed in the upper wall,and a series of branch synthetic faults which constitute the imbricate wedge fan are developed in the foot wall.Finally,these thrust faults terminate in the gypsum-salt rocks below the back-thrust fault.The high-angle basement-involved thrust faults have been formed by the reverse displacement of pre-existing normal faults,which dominate the local structural deformation in the foot wall.The occurrence of high-angle thrust and the reverse of the pre-existing normal fault may be related to the vertical shearing caused by the uplift of West Kunlun.
Through comprehensive analysis of the surface geology,seismic profile and continuous electromagnetic profile(CEMP) data in west Kunlun piedmont thrust belt in southwestern depression of Tarim basin,a non subduction-like contraction structure interpretation model with the layering contraction and vertically stacking style is proposed,which means that different styles of structural contraction and deformation occur in shallow and mid-deep layers owing to the detachments caused by the salt-gypsum rocks of Upper Cretaceous-Paleocene and competent strata's distribution in vertical direction.It seems that the detachment fault could not be stacked with another regional detachment fault whose horizontal displacement is great.The Cenozoic competent strata above the shallow salt layer are dominated by decollement fold deformation,which appears near perpendicular and symmetrical long-axis anticline,being parallel to the orogenic belt.The Mesozoic of middle subsalt layer and the deep basement rock formation in this basin are dominated by tenacious contraction deformation,and a series of basement-involved thrust faults with high-angle dipping to West Kunlun are developed.Thrust uplift may be formed in the upper wall,and a series of branch synthetic faults which constitute the imbricate wedge fan are developed in the foot wall.Finally,these thrust faults terminate in the gypsum-salt rocks below the back-thrust fault.The high-angle basement-involved thrust faults have been formed by the reverse displacement of pre-existing normal faults,which dominate the local structural deformation in the foot wall.The occurrence of high-angle thrust and the reverse of the pre-existing normal fault may be related to the vertical shearing caused by the uplift of West Kunlun.
引文
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[2]曲国胜,李亦纲,张宁,等.塔里木西南缘(齐姆根弧)前陆构造及形成机理[J].地质评论,2004,50(6):567-576.
[3]陈新安,张新林,屈秋平.塔西南山前构造特征及含油气前景[J].新疆石油地质,1999,20(6):468-473.
[4]张达景,胡健民,蒙义峰,等.干涉背斜:塔里木盆地西南部齐姆根逆冲推覆构造的特征及其与油气的关系[J].地质通报,2007,26(3):266-274.
[5]伍秀芳,刘胜,汪新.帕米尔-西昆仑北麓新生代前陆褶皱冲断带构造剖面分析[J].地质科学,2004,39(2):260-271.
[6]秦都.塔里木盆地西南地区侏罗纪原型盆地类型与特征[J].石油与天然气地质,2005,26(6):831-838.
[7]罗金海,周鼎武,柳益群.塔里木盆地西南缘浅变质岩的时代确定及其地质意义[J].地层学杂志,2007,31(4):391-394.
[8]DeCelles P G,Giles K A.Foreland basin system[J].Basin Research,1986,8(1):105-123.
[9]漆家福,雷刚林,李明刚,等.库车坳陷克拉苏构造带的结构模型及其形成机制[J].大地构造与成矿学,2009,33(1):51-58.
[10]漆家福,陈书平,杨桥,等.准噶尔-北天山盆山过渡带构造基本特征[J].石油与天然气地质,2008,29(2):252-260.
[11]贾承造,魏国齐.“九五”期间塔里木盆地构造研究成果概述[J].石油勘探与开发,2003,30(1):11-14.
[12]刘胜,汪新,伍秀芳,等.塔西南山前晚新生代构造生长地层与变形时代[J].石油学报,2004,25(5):24-28.
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