The Study On Sequence Stratigraphy And Sedimentary System Of Mid-Lower Jurassic In Northwestern Tarim

Based on the comprehensive study of the previous research results,this paper takes the southeastern margin of the Tarim Basin in the north of Altun as the research area,and uses the data of field outcrop profile,logging,earthquake and paleontology,and points out the theory of sequence stratigraphy.Southeastern six wells and five outlying strata,and the study area is divided into two secondary sequences and five third-order sequences.According to the low-level field,High bit field will be each sequence of three points,which SQ1SQ2 equivalent to J1 s,SQ3 equivalent to J1 k,SQ4SQ5 equivalent to J2 y and J2 t.Through the observation of the outcrop profile,identify the core sedimentary facies sequence,combined with seismic facies and logging sedimentary facies study,identify the main sedimentary facies type.The results show that the sediments of the alluvial fan,fan delta,lake and swamp are mainly developed in the Lower Jurassic.It is believed that from the Early Jurassic to the Middle Jurassic,from the source area of the western Kunlun Mountains to the study area,the sedimentary facies has gradually transitioned with alluvial fan-shore facies.During the Early Jurassic period,the basin was at the beginning of the fault depression,and the sedimentary range was relatively small.The sedimentary grain size was relatively large.The sandy tasha group was mainly composed of alluvial fan,alluvial plain and shore-During the Middle Jurassic period,the transition from the basin to the depression-depression occurred,the sedimentation area increased,the lake surface increased,and the sedimentary facies was still in the alluvial fan-lake transition,fan delta and fan delta front subfacies.Minfeng Depression and Weishixia Depression.Based on this analysis,the distribution pattern of the sedimentary facies is controlled by the structural factors of the sequence-depositional filling.The Jurassic in the study area is NEE to the long and narrow strip along the piedmont,Fengxie depression and the Yashigou depression area,the source area for the southern East Kunlun Mountains.