Characteristics and genetic mechanism of Mesozoic fault system in Lunnan area,Tarim Basin
In order to reveal the characteristics and development mechanism of Mesozoic fault system in Lunnan area,Based on the analysis method of fault structure,the types,geometric characteristics and genetic evolution of Mesozoic fault system are studied deeply in Lunnan area.The results show that the Mesozoic fracture system is dominated by tensional fault and tension-torsion fault in Lunnan area.The tensional fault system is mainly distributed in Lunxi platform area,Lunnan fault horst zone and Sangtamu fault horst zone.The fault scale of the tensional fault system is large,the profile is"eight"shaped fault combination and graben-horst structure,and the plane is NE and EW-trending banded distribution.The tension-torsion fault system is distributed in the whole area.The fault scale of the tension-torsion fault system is small,the profile is negative flower,graben and stepped combination style,and the plane is NE,and nearly SN to echelon distribution.Controlled by mid-Caledonian strike-slip faults,Mesozoic tension-torsional faults developed.Controlled by the anticlinal arching of the thrust fault in Hercynian period,Mesozoic tensional faults developed.The evolution of the fault system can be divided into three stages,namely,middle Caledonian strike-slip fault stage,Hercynian thrust fault stage and Indosinian-Yanshanian tensional fault and tension-torsion fault stage.Detailed interpretation of faults at Cambrian bottom surface to Triassic bottom surface stratigraphic interval in Lunnan area show that the No.2 tensional fault zone,No.8 and No.9 tension-torsional fault zones are the three major connect downward to the source rock of the basin.In these three areas,some faults cut upward through Cambrian bottom surface to Triassic bottom surface,which is good for hybrocarbon migration from Paleozoic to Mesozoic strata.These areas,therefore,is good for future exploration in Lunnan area.
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