Comprehensive Geophysical Study On Stratigraphic Distribution Regularities And Tectonic Frameworks In The Barkol Basin

The Barkol Basin is sandwiched between the Maqinwula Island Arc and the Harlic Island Arc.Until now,its internal stratigraphic distribution,fault structure,hydrocarbon accumulation and basin-mountain relationship are still not clear.In this paper,geophysical and geological methods such as magnetotelluric sounding,aeromagnetic,and seismic methods are adopted to carry out comprehensive research.The study is of great theoretical and scientific significance to the understanding of the stratigraphic distribution and tectonic framework of the Barkol Basin,as well as to the future oil and gas exploration of the basin.Geophysical characteristics show that magnetic anomalies in the eastern part of the basin show high number,indicating the distribution of volcanic rocks.The north-central and south-eastern parts of the basin are mainly composed of the lower carboni-ferous quomen-men-formation and the shore-shallow Marine facies.The shirenzi vol-canic system in the north is formed by fissure volcanic eruption,and the main litholo-gy is middle base volcanic lava and eruptive rock?mainly sedimentation tuff?.It can be seen from the seismic reflection profile that the seismic reflection in phase axis corresponding to the bottom interface of the paleogene is strong reflection and has good continuity.The reflection in phase axis corresponding to the bottom of inter-facing of the quaternary system is strong reflection with general continuity.The refl-ection in phase axis of Permian and carboniferous is not obvious and the continuity is poor.The strata above the paleogene are relatively gentle and the waveform changea little.The Barkol basin is divided into 5 electrical layers and rock masses,and Q strata is the second high resistivity layer,E and N strata are the middle and low resisti-vity layers,Mz and P₂stratum are the low resistivity layers,Cenozoic strata is the second high resistivity layer,D-O is the high resistivity layer,and rock mass is the high resis-tivity feature.The 11electrical-magnetic profiles show that the Barkol basin is mainly a sedimentary basin of the upper Paleozoic.The P₁+Cstrata deposit inthe upper Paleozoic was relatively stable,with a maximum thickness of about 3000 m,which was generally characterized by fault depression.The petrophysical resistivity characteristics are basically consistent with the formation resistivity characteristics,it proves that the inversion characteristics of formation resistivity are accurate.The research results show that The Cenozoic sediments are relatively thin,and the Mesozoic and Upper Permian strata have the characteristics of thinning gradually from the center of the basin to the periphery.The Lower Permian and Carboniferous strata are characterized by thick Piedmont deposits and thinning southward.There are 12 faults in the basin,the strike of which is nearly east-west,most of which are thrust faults.These faults constitute the basic tectonic framework of the study area.The basin is divided into three secondary structural units:the northern slope,the Harlik thrust belt and the Barkol depression.The Dahe structure in the Barkol depression is a favorable area for hydrocarbon accumulation.The southern Mount Harlic is thrusting northwest into the basin that are bounded by the Harlik fault.The basin and the northern Mt.Maqinwula fault are bounded by the Mt.Maqinwula fault,and the western Mt.Bogda fault is bounded by the Dongwu fault.