Study On The Characteristics Of Buried Fault Structures In The North Of The Songliao Basin

For a long time,geological research in Songliao Basin has been focused on meso-Cenozoic strata.With the deepening of exploration in recent years,it is found that the carboniferous-Permian strata in the basin have a good oil and gas prospect.In this paper,the buried faults developed in the carboniferous and Permian strata in the northern part of Songliao Basin are taken as the research object.Based on the gravity data and combined with regional aeromagnetic,magnetotagnetic and regional geological data,the deep buried faults are classified,and their structural characteristics,forming stages and mechanisms are discussed.In this paper,a large number of geophysical data in the research area are collected and the characteristics of geophysical anomalies are summarized.The gravity and magnetic anomalies are mainly interpreted in combination with geological,drilling and seismic data,and the following understandings are obtained by referring to previous research results:(1)To obtain the characteristics of the deep anomaly field in the study area by using the gravity and magnetic anomaly plan after the upper extension of 15 km and the wavelet transform.The deep structure in the study area still shows n NE trend on the whole.According to the marks of faults in the gravity and magnetic anomalies,it is preliminarily inferred that there are roughly two groups of faults in the study area: n NE and NW.(2)The 25 fractures in the cut Carboniferous-Permian strata were identified by using the total gravity gradient anomaly after stripping treatment,and their vertical characteristics were obtained according to the electrical and seismic data.According to the geometrical characteristics and distribution relations of the faults,it is basically determined that the n W trending faults formed later than the NNE trending faults.(3)Based on the summary of plate movement since late Paleozoic in northeast China,it is concluded that the carboniferous-Permian geological bodies in the study area have been strongly influenced by the Pacific tectonic domain since Mesozoic.Since the Mesozoic era,the Izenazaki plate subducted along the NW direction,which made the crust in the study area in this period under the tensile environment,and the NE-NNE faults developed greatly.During the late Cretaceous,the formation of the Pacific plate began to drift towards the Eurasian continent,which changed the stress field environment of the study area.Underthe action of a left-handed torsional stress,several large NW-trending strike-slip faults developed in the study area.