Study On Structural Characteristics Of The Tianjingshan Region Of The Longmenshan North Section

The Tianjingshan region of the Longmenshan north section belongs to theforeland thrust belt of the Longmenshan orogenic belt (Overthrust Belt). The oil andgas area of the foreland thrust belt composed of thrust belt and front type subductionarea under the impact of the squeeze dynamics,which is one of the world’s mostabundant types of oil and gas area.The structure and causes of the Longmenshanorogenic belt have always attracted attention of both domestic and abroadgeologists,so the Longmenshan orogenic belt has become the hot spot of structuralgeology research work.As the oil and gas exploration is gradually going deep into theorogenic belt from foreland basin, it is more and more important to do research on thetectonic characteristics, tectonic formation mechanism and tectonic evolution,however,the complex tectonic problems increasingly become a constraint on the current oil andgas exploration. In order to get breakthroughs on oil and gas exploration in such acomplex tectonic as orogenic belt piedmont tectonic belt,tectonic research plays abasic role in providing correct understanding of structural geology for decisionmaking of the oil and gas exploration.Therefore, deepening study on tectonicdeformation charateristics and evolution rules of Tianjingshan district inLongmenshan northern section is very important in both theory and practice to searchnew favorable exploration areas in Tianjingshan district.This paper will play animportant guiding role in clearing the direction of oil and gas exploration of thestudied areas and reducing exploration risk.This study has established the complex structrural model of the Longmenshanpiedmont zone Tianjingshan district basing on field investigation and data of drilling,well logging and seismic profile, by making full use of such new theory and methodsas extensional tectonics, compressional tectonics, inversion tectonics and fault-related fold structures.This paper has also done an in-depth and systematic research ongeometric features,deformation features and structural dynamics mechanism ofTianjingshan structure by such research means as regional tectonic setting researchand seismic interpretation.This paper has got the following results:1)Tianjingshandistrict has extensively developed such tectonic styles as gravity slidingstructure,fault-bend fold structure,overturned anticline structure,crowded away fromthe wedge structure, double structure,rushed up structure and imbricate structure.2) Inin the vertical direction of Tianjingshan region, there are three regional-baseddetachment systems: shallow detachment systems, purple shale of Feixianguan groupsupper part; the belly layer detachment systems is in the lower part of Cambrian of theYangtze ditch group; the deep detachment systems is strata Presinian.3)The formationof Tianjingshan structure has gone through four phases:Caledonian-early Indo-Chinais in the extensional dynamic environment; the late Indosinian movement is in thesqueeze dynamic environment; Yanshan movement is mainly vertical lifting effect;Himalayan movement period is mainly the powerful compression for the North West-South East.4) The Tianjingshan structure were divided into three tectonic units in thispaper: the shallow nappe tectonic units, the central thrust nappe tectonic units andabdominal nappe tectonic units.