Tectonic Interpretation Of The Seismic Profiles In The Lianhuashan Area In The Southern Part Of Western Sichuan Foreland Basin

Hydrocarbon exploration in the western Sichuan foreland basin is a hot spot allalong. For decades, many famous geologists research the characteristics ofthe western Sichuan with different ways, and come out with lots ofimportant opinions. These effectively guide the oil and gas exploration in thewestern Sichuan foreland basin. But recent years, the facts of the artesianwells in the Lianhuashan regions where locate in the south of the westernSichuan basin indicate that the folds and tectonics are dissimilar with the existingunderstanding. So that to reknow the underground structure in the regions are veryexigent.The western Sichuan basin is a multigenetic superimposed basin of theprototype basins since Sinian, including the marine cratonic basin,the fault basin,thesag basin and the foreland basin. The change of the tectonic dynamic environment indifferent periods cause the alternation and formation of the basins. But these basins isnot absolute superposition with a single way, always with the change of thetectonodynamics environment in later stage alter the early prototype basin. Thelithosomic bodies in the prototype basin which have been formed in different periodsare not same.The geometry and features of the subsurface faults and folds in the Lianhuashanregion are discussed on the basis of the interpretation of the seismic profiles inintegration with the research of the forerunners and the evolution of the Longmenshanmountains and the western Sichuan basin.Finally come to the following conclusions:1. With the main clue of basin-orogen coupling dynamic evolution, the studyreveals that western Sichuan basin and Sichuan basin both have the same thermal evolution history. They both went throng Pre-Sinian extrusion, Simian to Permianextension, Triassic and Jurassic transition, and extrusion since the Cretaceous. In thisprocess, the Triassic and Jurassic transition phase went throng from the early tension tothe late extrusion, and was the stage of the formation and expansion of SichuanTerrestrial Basin.2. From the viewpoint of the superimposed basin, according to sedimentary basinsequence and the dynamic characteristics of basin-orogen coupling evolution, Thewestern sichuan basin will be divided into four prototype basin: Sinian-Triassic stablecratonic basin development stage; the rift basin development stage in the 1st-3rdmember of Xujiahe Formation in Late Triassic; Basin development stage from the 4thmember of Xujiahe Formation in Late Triassic to Shaximiao Formation in MiddleJurassic; Foreland basin development stage since Late Jurassic.3. According to detailed seismic interpretation and field survey data, we considerthat the Xinkaidian fault, Mengdingshan fault and Zhongli fault are shallow thrust faultwhich are Himalayan movement products.4. Through detailed seismic interpretation and the study of previous research,there are three large reverse faults to control the tectonic evolution of the area, whichare Daxi—Shuanshi fault, Lushan fault and Mengquanyuan fault. They are successionand development of previous fault.5. According to detailed seismic interpretation and field survey data,Mengquanyuan fault is a multi-phase fault, which experience early tension and lateextrusion. The section is a positive-reversal tectonic style.6. According to detailed structure seismic interpretation, we discover thatMengdingshan anticline is fault-propagation fold, which performances as a typicalunsymmetrical box fold.