多世代旋转正断层对断陷盆地沉积迁移的控制——柴达木早、中侏罗世盆地性质
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摘要
基于盆-山耦合关系、地震剖面解释及盆地沉积特征,认为早侏罗世柴达木为箕状断陷盆地,具“南断北超”性质,中侏罗世亦为箕状断陷盆地,具“北断南超”性质。昆仑山北缘正断层与阿尔金左行、鄂拉山右行走滑断裂,分别控制了早侏罗世柴西、柴东箕状断陷盆地;随着昆仑山隆升向北扩展,北倾的高角度正断层逐渐旋转上凸,柴南早侏罗世地层逐渐剥蚀而缺失,仅残存于柴北缘鄂博梁、冷湖构造带等地区。下侏罗统与基底接触带发育的“鱼鳞式”构造,为地壳不均匀隆升时,多世代旋转正断层先后切割所致。柴西南隆升导致中侏罗世地层向北、北东迁移,并出现反向箕状断陷盆地。因此,柴达木早—中侏罗世箕状断陷盆地的反向与沉积迁移,记录了青藏高原北部地壳由水平拉张转换为垂向隆升并向北扩展的地质过程。
Based on the coupling relations between basins and mountains, interpretation of seismic sections and sedimentary characteristics of basins, the Early Jurassic Qaidam Basin is confirmed as a haft-graben fault basin with characters of "faulting in the south and overlapping in the north", while the Middle Jurassic Qaidam Basin as a haft-graben fault basin with the characters of "faulting in the north and overlapping in the south". Normal faults at the northern margin of the Kunlun Mountains, together with the left-lateral strike-slip Altun Tagh fracture and right-lateral strike-slip Elashan fracture, respectively, controlled the formation of Early Jurassic haft-graben fault basins in the western and eastern Qaidam Basin. Along with the uplift of the Kunlun Mountains expanding toward the north, north-inclined high-angle normal fault planes gradually rotated and rose, which resulted in a tectonic denudation and disappearance of Early Jurassic strata in the southern Qaidam Basin and relics of Early Jurassic strata are remained only in the Lenghu structural and Eboliang structural belts and other belts in the southern Qaidam Basin. Fish-scale-like structures formed at the contact surface between lower Jurassic and basement might result from mutual incision of multi-generation rotary normal faults in turn because of asymmetrical uplift of crust. Uplift in the southwestern Qaidam Basin led to the migration of Middle Jurassic strata to the north and west, and resulted in the formation of inverted haft-graben fault basin. Therefore, the dip of normal faults controlling the Early Jurassic haft-graben fault basins was contrary to that of the Middle Jurassic haft-graben fault basins, and there was a sedimentary migration from the Early Jurassic to Middle Jurassic. It recorded a geological process that the crust of the northern Qinghai—Tibetan Plateau changed from horizontal extension to vertical uplift.
Based on the coupling relations between basins and mountains, interpretation of seismic sections and sedimentary characteristics of basins, the Early Jurassic Qaidam Basin is confirmed as a haft-graben fault basin with characters of "faulting in the south and overlapping in the north", while the Middle Jurassic Qaidam Basin as a haft-graben fault basin with the characters of "faulting in the north and overlapping in the south". Normal faults at the northern margin of the Kunlun Mountains, together with the left-lateral strike-slip Altun Tagh fracture and right-lateral strike-slip Elashan fracture, respectively, controlled the formation of Early Jurassic haft-graben fault basins in the western and eastern Qaidam Basin. Along with the uplift of the Kunlun Mountains expanding toward the north, north-inclined high-angle normal fault planes gradually rotated and rose, which resulted in a tectonic denudation and disappearance of Early Jurassic strata in the southern Qaidam Basin and relics of Early Jurassic strata are remained only in the Lenghu structural and Eboliang structural belts and other belts in the southern Qaidam Basin. Fish-scale-like structures formed at the contact surface between lower Jurassic and basement might result from mutual incision of multi-generation rotary normal faults in turn because of asymmetrical uplift of crust. Uplift in the southwestern Qaidam Basin led to the migration of Middle Jurassic strata to the north and west, and resulted in the formation of inverted haft-graben fault basin. Therefore, the dip of normal faults controlling the Early Jurassic haft-graben fault basins was contrary to that of the Middle Jurassic haft-graben fault basins, and there was a sedimentary migration from the Early Jurassic to Middle Jurassic. It recorded a geological process that the crust of the northern Qinghai—Tibetan Plateau changed from horizontal extension to vertical uplift.
引文
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陈宣华,尹安,GeorgeEGehrels,等.2002.青藏高原北缘中生代伸展构造、40Ar/39Ar测年和MDD模拟.地球学报,23(4):305～310.
曹国强,陈世悦,徐凤银,等.2005.柴达木盆地西部中—新生代沉积构造演化.中国地质,32(1):33～40.
邓晋福,吴宗絮,杨建军,等.1995.格尔木—额济纳旗地学断面走廊域地壳—上地幔岩石学结构与深部过程.地球物理学报,38(增刊):130～144.
葛肖虹,刘俊来.2000.被肢解的“西域克拉通”.岩石学报,16(1):59～66.
刘和甫,梁慧社,李晓清,等.2000.中国东部中新生代裂陷盆地与伸展山岭耦合机制.地学前缘,7(4):477～486.
马杏垣,刘和甫,王维襄.1983.中国东部中新生代裂陷作用及伸展构造.地质学报,57(1):22～32.
孙延贵,张国伟,王瑾,等.2004.秦昆接合区两期基性岩墙群40Ar/39Ar定年及其构造意义.地质学报,78(1):65～71.
汤良杰,张一伟,金之钧,等.2004.塔里木盆地、柴达木盆地的开合旋回.地质通报,23(3):254～260.
夏文臣,张宁,袁晓萍,等.1998.柴达木侏罗系的构造层序及前陆盆地演化.石油与天然气地质,19(3):173～180.
翟光明,徐凤银,李建青.1997.重新认识柴达木盆地力争油气勘探获得新突破.石油学报,18(2):1～7.
周建勋,徐凤银,胡勇.2003.柴达木盆地北缘中、新生代构造变形及其对油气成藏的控制.石油学报,24(1):19～24.
张克信,黄继春,殷鸿福,等.1999.放射虫等生物群在非史密斯地层研究中的应用～以东昆仑阿尼玛卿混杂岩带为例.中国科学(D辑),29(6):542～550.
AnupmaG,ChristopherH,ScholzCH.2000.Amodelofnormalfaultinteractionbasedonobservationsandtheory.JournalofStructuralGeology,22:865～879.
ContrerasJ,AndersMH,ScholzCH.2000.Growthofanormalfaultsystem:observationsfromtheLakeMalawibasinoftheeastAfricanrift.JournalofStructuralGeology,22:159～168.
ListerGS,DavisGA.1989.TheoriginofmetamorphiccorecomplexesanddetachmentfaultsformedduringTertiaryinthenorthernColoradoriverregion,U.S.A.J.Structure,11:65～94.
WernickeB,BurchfieBC.1982.Modelofextensionaltectonics.JournalofStructuralGeology,4:105～115.
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