库车褶皱-冲断带前缘盐层厚度对滑脱褶皱构造特征及演化的影响
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摘要
库车褶皱-冲断带前缘发育一系列滑脱褶皱,虽然卷入变形的新生代地层及底部滑脱层(古近系盐层)相同,但滑脱褶皱的构造特征及演化存在显著差异。文中结合野外地质调查结果以及钻井资料和高品质二维地震反射剖面解析,以南喀背斜和米斯坎塔克背斜为例,估算出盐层初始厚度,并讨论其对于滑脱褶皱样式及其演化过程的影响。结果表明,南喀背斜和米斯坎塔克背斜下伏盐层初始厚度不同,估算出前者厚度介于0.1~0.5km,主要为0.1~0.3km,而后者却大约为1.0km。与此同时,南喀背斜和米斯坎塔克背斜均表现出分段差异变形特征。南喀背斜为低缓的滑脱褶皱,其东段隐伏地下,变形方式为褶皱作用;而西段出露地表,背斜核部发育隐伏的逆冲断层,变形方式为褶皱作用和断层作用。背斜西段平均隆升速率大于东段,导致西段隆升出露地表。米斯坎塔克背斜表现为大规模滑脱褶皱,根据变形特征的不同可以分为3段,东段背斜倾向北,盐岩在其核部及北翼下方聚集加厚;而中—西段背斜倾向南,其中中段背斜核部位置盐岩聚集加厚,两翼下伏盐岩减薄甚至形成盐焊接。而在西段背斜呈箱状,两翼下方盐岩厚度至少为1.0km。笔者总结出库车褶皱-冲断带前缘发育的7种滑脱褶皱变形样式,通过构造分析得出,研究区滑脱褶皱的变形主要受盐层厚度、构造缩短量及盐岩流动变形共同控制,其中盐层厚度起主导作用,控制了滑脱褶皱的发育位置,并影响了滑脱褶皱的变形样式。研究结果将为其他褶皱-冲断带中滑脱褶皱的相关研究提供重要参考,特别是在缺少高品质地震资料,或者构造变形强烈、地震资料品质较差的地区。
Detachment folds are widely distributed in the leading edge of Kuqa fold and thrust belt(KFTB).Although the Cenozoic sedimentary strata involved into the structural deformation and their underlying basal detachment(Paleogene salt layer)are the same,the structural characteristics and the evolution of detachment folds are quite different.In this paper,on the basis of the field observations and the interpretations of highquality seismic and well data,we demonstrate the initial salt layer thickness and discuss their relations to the deformation styles and the evolution of detachment folds,taking the examples from the Nanka and Misikantage anticlines.The results of our analysis indicate that the initial underlying salt layer of Nanka anticline is about0.1-0.5km in thickness,generally of 0.1-0.3km,which is in contrast to the Misikantage anticline with thickness of as much as~1.0km.Meanwhile,the along-strike variations in the structural styles have been observed both in the Nanka and Misikantage anticlines.The Nanka anticline is a low-amplitude detachment fold,whose eastern segment is buried under the ground surface and characterized by the folding deformation.However,in its western segment the fold with relative higher average uplift-rate is consequently exposed on the surface associated with both folding and thrusting,as evidenced by thrust faults developed at the core of anticline.In contrast,the Misikantage anticline is a large-scale detachment fold,which can be divided into three segments of different geometry.The north-vergence of the anticline in the eastern segment are different from the south-vergence of the anticline in the central and western segments.Meanwhile,thick salt is mainly accumulated underlying the north limb and at the core of anticline in the eastern segment,which is in contrast to the salt accumulated at the core of anticline,thinning towards both limbs and even forming the salt welds in the central segment,and also obviously different from the box-fold with underlying salt layer of at least 1km in thickness in the western segment.In summary,seven distinct deformation styles of detachment folds in the leading edge of KFTB have been demonstrated,and,according to our analysis,the deformation style of detachment fold was strongly affected by the salt layer thickness,compressive shortening and salt flow.Among them,the salt layer thickness was dominative in controlling the deformation style of detachment fold.The results of this study concerning about the structural characteristics and evolution of detachment folds and their controlling factors might be helpful for the investigations of the detachment folds in other fold and thrust belts,especially within the regions without high-quality seismic data or poor quality due to intense strutural deformation.
Detachment folds are widely distributed in the leading edge of Kuqa fold and thrust belt(KFTB).Although the Cenozoic sedimentary strata involved into the structural deformation and their underlying basal detachment(Paleogene salt layer)are the same,the structural characteristics and the evolution of detachment folds are quite different.In this paper,on the basis of the field observations and the interpretations of highquality seismic and well data,we demonstrate the initial salt layer thickness and discuss their relations to the deformation styles and the evolution of detachment folds,taking the examples from the Nanka and Misikantage anticlines.The results of our analysis indicate that the initial underlying salt layer of Nanka anticline is about0.1-0.5km in thickness,generally of 0.1-0.3km,which is in contrast to the Misikantage anticline with thickness of as much as~1.0km.Meanwhile,the along-strike variations in the structural styles have been observed both in the Nanka and Misikantage anticlines.The Nanka anticline is a low-amplitude detachment fold,whose eastern segment is buried under the ground surface and characterized by the folding deformation.However,in its western segment the fold with relative higher average uplift-rate is consequently exposed on the surface associated with both folding and thrusting,as evidenced by thrust faults developed at the core of anticline.In contrast,the Misikantage anticline is a large-scale detachment fold,which can be divided into three segments of different geometry.The north-vergence of the anticline in the eastern segment are different from the south-vergence of the anticline in the central and western segments.Meanwhile,thick salt is mainly accumulated underlying the north limb and at the core of anticline in the eastern segment,which is in contrast to the salt accumulated at the core of anticline,thinning towards both limbs and even forming the salt welds in the central segment,and also obviously different from the box-fold with underlying salt layer of at least 1km in thickness in the western segment.In summary,seven distinct deformation styles of detachment folds in the leading edge of KFTB have been demonstrated,and,according to our analysis,the deformation style of detachment fold was strongly affected by the salt layer thickness,compressive shortening and salt flow.Among them,the salt layer thickness was dominative in controlling the deformation style of detachment fold.The results of this study concerning about the structural characteristics and evolution of detachment folds and their controlling factors might be helpful for the investigations of the detachment folds in other fold and thrust belts,especially within the regions without high-quality seismic data or poor quality due to intense strutural deformation.
引文
[1]Jamison W R.Geometric analysis of fold development in overthrust terranes[J].Journal of Structural Geology,1987,9(2):207-219.
[2]Poblet J,McClay K.Geometry and kinematics of single-layer detachment folds[J].AAPG Bulletin,1996,80(7):1085-1109.
[3]Suppe J.Geometry and kinematics of fault-bend folding[J].American Journal of Science,1983,283(7):684-721.
[4]Suppe J,Connors C D,Zhang Y.Shear fault-bend folding[M]∥McClay K R.Thrust Tectonics and Hydrocarbon Systems.AAPG Memoir 82.Tulsa:AAPG,2004:303-323.
[5]Suppe J,Medwedeff D A.Geometry and kinematics of faultpropagation folding[J].Eclogae Geologicae Helvetiae,1990,83(3):409-454.
[6]Mitra S.Fault-propagation folds:Geometry,kinematic evolution,and hydrocarbon traps[J].AAPG Bulletin,1990,74(6):921-945.
[7]Shaw J H,Connors C D,Suppe J.Seismic Interpretation of Contractional Fault-Related Folds[M].AAPG Studies in Geology 53.Tulsa:AAPG,2005.
[8]McClay K,Shaw J H,Suppe J.Thrust Fault-Related Folding[M].AAPG Memoir 94.Tulsa:AAPG,2011.
[9]Dahlstrom C D A.Geometric constraints derived from the law of conservation of volume and applied to evolutionary models for detachment folding[J].AAPG Bulletin,1990,74(3):336-344.
[10]Epard J L,Groshong R H.Kinematic model of detachment folding including limb rotation,fixed hinges and layer-parallel strain[J].Tectonophysics,1995,247:85-103.
[11]Homza T X,Wallace W K.Geometric and kinematic models for detachment folds with fixed and variable detachment depths[J].Journal of Structural Geology,1995,17(4):575-588.
[12]Atkinson P K,Wallace W K.Competent unit thickness variation in detachment folds in the Northeastern Brooks Range,Alaska:Geometric analysis and a conceptual model[J].Journal of Structural Geology,2003,25(10):1751-1771.
[13]Mitra S.A unified kinematic model for the evolution of detachment folds[J].Journal of Structural Geology,2003,25(10):1659-1673.
[14]Wilkerson M S,Smaltz S M,Bowman D R,et al.2-D and 3-D modeling of detachment folds with hinterland inflation:A natural example from the Monterrey Salient,northeastern Mexico[J].Journal of Structural Geology,2007,29(1):73-85.
[15]Stewart S A.Influence of detachment layer thickness on style of thin-skinned shortening[J].Journal of Structural Geology,1996,18(10):1271-1274.
[16]Stewart S A.Geometry of thin-skinned tectonic systems in relation to detachment layer thickness in sedimentary basins[J].Tectonics,1999,18(4):719-732.
[17]Gonzalez-Mieres R,Suppe J.Relief and shortening in detachment folds[J].Journal of Structural Geology,2006,28(10):1785-1807.
[18]Suppe J.Mass balance and thrusting in detachment folds[M]∥McClay K,Shaw J H,Suppe J.Thrust Fault-Related Folding.AAPG Memoir 94.Tulsa:AAPG,2011:21-37.
[19]Chen S P,Tang L J,Jin Z J,et al.Thrust and fold tectonics and the role of evaporites in deformation in the Western Kuqa Foreland of Tarim Basin,Northwest China[J].Marine and Petroleum Geology,2004,21(8):1027-1042.
[20]卢华复,贾东,陈楚铭,等.库车新生代构造性质和变形时间[J].地学前缘,1999,6(4):215-221.
[21]汪新,贾承造,杨树锋,等.南天山库车冲断褶皱带构造变形时间:以库车河地区为例[J].地质学报,2002,76(1):55-63.
[22]唐鹏程,汪新,谢会文,等.库车坳陷却勒地区新生代盐构造特征、演化及变形控制因素[J].地质学报,2010,84(12):1735-1745.
[23]李世琴,唐鹏程,饶刚.南天山库车褶皱-冲断带喀拉玉尔滚构造带新生代变形特征及其控制因素[J].地球科学:中国地质大学学报,2013,38(4):859-869.
[24]Li S Q,Wang X,Suppe J.Compressional salt tectonics and synkinematic strata of the western Kuqa foreland basin,southern Tian Shan,China[J].Basin Research,2012,24(4):475-497.
[25]Yin A,Nie S,Craig P,et al.Late Cenozoic tectonic evolu-tion of the southern Chinese Tian Shan[J].Tectonics,1998,17(1):1-27.
[26]唐鹏程,李世琴,雷刚林,等.库车褶皱-冲断带拜城凹陷盐构造特征与成因[J].地球科学:中国地质大学学报,2012,37(1):69-76,92.
[27]汤良杰,金之钧,贾承造,等.库车前陆褶皱-冲断带前缘大型盐推覆构造[J].地质学报,2004,78(1):17-25.
[28]汤良杰,贾承造,金之钧,等.库车前陆褶皱冲断带中段第三系盐枕构造[J].地质科学,2003,38(3):281-290.
[29]余一欣,汤良杰,杨文静,等.库车前陆褶皱-冲断带前缘盐构造分段差异变形特征[J].地质学报,2007,81(2):166-173.
[30]余一欣,汤良杰,殷进垠,等.应用平衡剖面技术分析库车坳陷盐构造运动学特征[J].石油学报,2008,29(3):378-382.
[31]Hardy S,Poblet J.Geometric and numerical model of progressive limb rotation in detachment folds[J].Geology,1994,22(4):371-374.
[32]Poblet J,Mcclay K,Storti F,et al.Geometries of syntectonic sediments associated with single-layer detachment folds[J].Journal of Structural Geology,1997,19(3/4):369-381.
[33]Poblet J,Muoz J A,TravéA,et al.Quantifying the kinematics of detachment folds using three-dimensional geometry:Application to the Mediano anticline(Pyrenees,Spain)[J].Geological Society of America Bulletin,1998,110(1):111-125.
[34]Mitra S.Structural models of faulted detachment folds[J].AAPG Bulletin,2002,86(9):1673-1694.
[35]李世琴.南天山库车前陆盆地中—西段挤压盐构造及同构造沉积地层研究[D].杭州:浙江大学,2009:1-147.
[36]Rowan M G,Trudgill B D,Fiduk J C.Deep-water,saltcored fold belts:Lessons from the Mississippi Fan and Perdido fold belts,northern Gulf of Mexico[M]∥Mohriak W,Talwani M.Atlantic Rifts and Continental Margins.Geophysical Monograph 115.Washington DC:American Geophysical Union,2000:173-191.
[37]Costa E,Vendeville B C.Experimental insights on the geometry and kinematics of fold-and-thrust belts above weak,viscous evaporitic decollement[J].Journal of Structural Geology,2002,24(11):1729-1739.
[38]Rowan M G,Peel F J,Vendeville B C.Gravity-driven fold belts on passive margins[M]∥McClay K R.Thrust Tectonics and Hydrocarbon Systems.AAPG Memoir 82.Tulsa:AAPG,2004:157-182.
[39]陈书平,汤良杰,贾承造.含盐前陆充填变形前缘盐上层构造样式[J].地球学报,2004,25(5):561-564.
[40]Cotton J T,Koyi H A.Modeling of thrust fronts above ductile and frictional detachments:Application to structures in the Salt Range and Potwar Plateau,Pakistan[J].Geological Society of America Bulletin,2000,112(3):351-363.
[41]汪新,王招明,谢会文,等.塔里木库车坳陷新生代盐构造解析及其变形模拟[J].中国科学:地球科学,2010,40(12):1655-1668.
[2]Poblet J,McClay K.Geometry and kinematics of single-layer detachment folds[J].AAPG Bulletin,1996,80(7):1085-1109.
[3]Suppe J.Geometry and kinematics of fault-bend folding[J].American Journal of Science,1983,283(7):684-721.
[4]Suppe J,Connors C D,Zhang Y.Shear fault-bend folding[M]∥McClay K R.Thrust Tectonics and Hydrocarbon Systems.AAPG Memoir 82.Tulsa:AAPG,2004:303-323.
[5]Suppe J,Medwedeff D A.Geometry and kinematics of faultpropagation folding[J].Eclogae Geologicae Helvetiae,1990,83(3):409-454.
[6]Mitra S.Fault-propagation folds:Geometry,kinematic evolution,and hydrocarbon traps[J].AAPG Bulletin,1990,74(6):921-945.
[7]Shaw J H,Connors C D,Suppe J.Seismic Interpretation of Contractional Fault-Related Folds[M].AAPG Studies in Geology 53.Tulsa:AAPG,2005.
[8]McClay K,Shaw J H,Suppe J.Thrust Fault-Related Folding[M].AAPG Memoir 94.Tulsa:AAPG,2011.
[9]Dahlstrom C D A.Geometric constraints derived from the law of conservation of volume and applied to evolutionary models for detachment folding[J].AAPG Bulletin,1990,74(3):336-344.
[10]Epard J L,Groshong R H.Kinematic model of detachment folding including limb rotation,fixed hinges and layer-parallel strain[J].Tectonophysics,1995,247:85-103.
[11]Homza T X,Wallace W K.Geometric and kinematic models for detachment folds with fixed and variable detachment depths[J].Journal of Structural Geology,1995,17(4):575-588.
[12]Atkinson P K,Wallace W K.Competent unit thickness variation in detachment folds in the Northeastern Brooks Range,Alaska:Geometric analysis and a conceptual model[J].Journal of Structural Geology,2003,25(10):1751-1771.
[13]Mitra S.A unified kinematic model for the evolution of detachment folds[J].Journal of Structural Geology,2003,25(10):1659-1673.
[14]Wilkerson M S,Smaltz S M,Bowman D R,et al.2-D and 3-D modeling of detachment folds with hinterland inflation:A natural example from the Monterrey Salient,northeastern Mexico[J].Journal of Structural Geology,2007,29(1):73-85.
[15]Stewart S A.Influence of detachment layer thickness on style of thin-skinned shortening[J].Journal of Structural Geology,1996,18(10):1271-1274.
[16]Stewart S A.Geometry of thin-skinned tectonic systems in relation to detachment layer thickness in sedimentary basins[J].Tectonics,1999,18(4):719-732.
[17]Gonzalez-Mieres R,Suppe J.Relief and shortening in detachment folds[J].Journal of Structural Geology,2006,28(10):1785-1807.
[18]Suppe J.Mass balance and thrusting in detachment folds[M]∥McClay K,Shaw J H,Suppe J.Thrust Fault-Related Folding.AAPG Memoir 94.Tulsa:AAPG,2011:21-37.
[19]Chen S P,Tang L J,Jin Z J,et al.Thrust and fold tectonics and the role of evaporites in deformation in the Western Kuqa Foreland of Tarim Basin,Northwest China[J].Marine and Petroleum Geology,2004,21(8):1027-1042.
[20]卢华复,贾东,陈楚铭,等.库车新生代构造性质和变形时间[J].地学前缘,1999,6(4):215-221.
[21]汪新,贾承造,杨树锋,等.南天山库车冲断褶皱带构造变形时间:以库车河地区为例[J].地质学报,2002,76(1):55-63.
[22]唐鹏程,汪新,谢会文,等.库车坳陷却勒地区新生代盐构造特征、演化及变形控制因素[J].地质学报,2010,84(12):1735-1745.
[23]李世琴,唐鹏程,饶刚.南天山库车褶皱-冲断带喀拉玉尔滚构造带新生代变形特征及其控制因素[J].地球科学:中国地质大学学报,2013,38(4):859-869.
[24]Li S Q,Wang X,Suppe J.Compressional salt tectonics and synkinematic strata of the western Kuqa foreland basin,southern Tian Shan,China[J].Basin Research,2012,24(4):475-497.
[25]Yin A,Nie S,Craig P,et al.Late Cenozoic tectonic evolu-tion of the southern Chinese Tian Shan[J].Tectonics,1998,17(1):1-27.
[26]唐鹏程,李世琴,雷刚林,等.库车褶皱-冲断带拜城凹陷盐构造特征与成因[J].地球科学:中国地质大学学报,2012,37(1):69-76,92.
[27]汤良杰,金之钧,贾承造,等.库车前陆褶皱-冲断带前缘大型盐推覆构造[J].地质学报,2004,78(1):17-25.
[28]汤良杰,贾承造,金之钧,等.库车前陆褶皱冲断带中段第三系盐枕构造[J].地质科学,2003,38(3):281-290.
[29]余一欣,汤良杰,杨文静,等.库车前陆褶皱-冲断带前缘盐构造分段差异变形特征[J].地质学报,2007,81(2):166-173.
[30]余一欣,汤良杰,殷进垠,等.应用平衡剖面技术分析库车坳陷盐构造运动学特征[J].石油学报,2008,29(3):378-382.
[31]Hardy S,Poblet J.Geometric and numerical model of progressive limb rotation in detachment folds[J].Geology,1994,22(4):371-374.
[32]Poblet J,Mcclay K,Storti F,et al.Geometries of syntectonic sediments associated with single-layer detachment folds[J].Journal of Structural Geology,1997,19(3/4):369-381.
[33]Poblet J,Muoz J A,TravéA,et al.Quantifying the kinematics of detachment folds using three-dimensional geometry:Application to the Mediano anticline(Pyrenees,Spain)[J].Geological Society of America Bulletin,1998,110(1):111-125.
[34]Mitra S.Structural models of faulted detachment folds[J].AAPG Bulletin,2002,86(9):1673-1694.
[35]李世琴.南天山库车前陆盆地中—西段挤压盐构造及同构造沉积地层研究[D].杭州:浙江大学,2009:1-147.
[36]Rowan M G,Trudgill B D,Fiduk J C.Deep-water,saltcored fold belts:Lessons from the Mississippi Fan and Perdido fold belts,northern Gulf of Mexico[M]∥Mohriak W,Talwani M.Atlantic Rifts and Continental Margins.Geophysical Monograph 115.Washington DC:American Geophysical Union,2000:173-191.
[37]Costa E,Vendeville B C.Experimental insights on the geometry and kinematics of fold-and-thrust belts above weak,viscous evaporitic decollement[J].Journal of Structural Geology,2002,24(11):1729-1739.
[38]Rowan M G,Peel F J,Vendeville B C.Gravity-driven fold belts on passive margins[M]∥McClay K R.Thrust Tectonics and Hydrocarbon Systems.AAPG Memoir 82.Tulsa:AAPG,2004:157-182.
[39]陈书平,汤良杰,贾承造.含盐前陆充填变形前缘盐上层构造样式[J].地球学报,2004,25(5):561-564.
[40]Cotton J T,Koyi H A.Modeling of thrust fronts above ductile and frictional detachments:Application to structures in the Salt Range and Potwar Plateau,Pakistan[J].Geological Society of America Bulletin,2000,112(3):351-363.
[41]汪新,王招明,谢会文,等.塔里木库车坳陷新生代盐构造解析及其变形模拟[J].中国科学:地球科学,2010,40(12):1655-1668.
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