Based on the field survey of Lower Jurassic Badaowan Formation(Fm.)in Changji area of Xinjiang,China,the authors studied the sedimentary environment and provenance characteristics using the analyses of stratigraphic p...Based on the field survey of Lower Jurassic Badaowan Formation(Fm.)in Changji area of Xinjiang,China,the authors studied the sedimentary environment and provenance characteristics using the analyses of stratigraphic profiles,sedimentary structures,petrography,zircon U-Pb chronology and geochemistry.The results show that Badaowan Fm.deposited in fluvial to swamp shallow-deeplacustrine sedimentary facies deposition.Contents of Sr and ratios of Sr/Cu,Sr/Ba,Th/U,SiO_(2)/Al_(2)O_(3),V/(V+Ni),V/Cr,and Cu/Zn together indicate that Badaowan Fm.was deposited in an oxygen-poor transitional freshwater environment,under humid climatic conditions.Geochemical characteristics and Q–F–L,Qm–E–Lt,Th–Co–Zr/10,La–Th–Sc,and Th–Sc–Zr/10 discrimination diagrams indicate that the tectonic setting of the source area was a continental island arc environment.Lithological composition,Th/U ratios,and Co/Th–La/Sc,La/Th–Hf,and La/Yb–REE discrimination diagrams show that the source rocks of Badaowan Fm.were upper-crust felsic volcanic rocks.U-Pb dating of detrital zircons yields ages of 1542.3±15.0 to 232.9±3.3 Ma and mostly in the ranges of 470–410 and 370–280 Ma.A comparison of these ages with the age data from different blocks of crystalline rock in Tianshan Mountains area reveals that the sedimentary rocks in the Badaowan Fm.were sourced predominantly from the central and subordinately from the southern Tianshan Mountains during Early Jurassic.展开更多
In order to determine the planar and volume distribution of sand bodies of the Jurassic Badaowan formation in Block T13 of Junggar basin,we used analysis of field outcrop and 3D seismic data,which play an essential ro...In order to determine the planar and volume distribution of sand bodies of the Jurassic Badaowan formation in Block T13 of Junggar basin,we used analysis of field outcrop and 3D seismic data,which play an essential role in areas of sparse well coverage.We describe sedimentary facies characteristics,sand body planforms,width and connectivity patterns of sand bodies,and vertical associations and successions by acoustic impedance inversion technology and sedimentological theory.Results of our study show braided fluvial strata deposits in the Jurassic Badaowan formation.Each sand body is approximately lenticular in shape.The width of each sand body falls in the range 100～800 m,with most between 200 and 400 m.The sand bodies vary in thickness from 4 to 13 m,with most below 9 m.The width/thickness ratios lie in the range 20～55.The connectivity of braided fluvial channel sand bodies is controlled by changes of accommodation space.One fining-upward sedimentary cycle of base-level rise is recognized in Badaowan formation,representing an upward rise of base level.The connectivity of sand bodies was found to be greatest in the early stage of base-level rise,becoming progressively worse with increasing base-level rise.展开更多
基金Supported by Geological Survey Project of China(No.K45E001012,2019–002).
文摘Based on the field survey of Lower Jurassic Badaowan Formation(Fm.)in Changji area of Xinjiang,China,the authors studied the sedimentary environment and provenance characteristics using the analyses of stratigraphic profiles,sedimentary structures,petrography,zircon U-Pb chronology and geochemistry.The results show that Badaowan Fm.deposited in fluvial to swamp shallow-deeplacustrine sedimentary facies deposition.Contents of Sr and ratios of Sr/Cu,Sr/Ba,Th/U,SiO_(2)/Al_(2)O_(3),V/(V+Ni),V/Cr,and Cu/Zn together indicate that Badaowan Fm.was deposited in an oxygen-poor transitional freshwater environment,under humid climatic conditions.Geochemical characteristics and Q–F–L,Qm–E–Lt,Th–Co–Zr/10,La–Th–Sc,and Th–Sc–Zr/10 discrimination diagrams indicate that the tectonic setting of the source area was a continental island arc environment.Lithological composition,Th/U ratios,and Co/Th–La/Sc,La/Th–Hf,and La/Yb–REE discrimination diagrams show that the source rocks of Badaowan Fm.were upper-crust felsic volcanic rocks.U-Pb dating of detrital zircons yields ages of 1542.3±15.0 to 232.9±3.3 Ma and mostly in the ranges of 470–410 and 370–280 Ma.A comparison of these ages with the age data from different blocks of crystalline rock in Tianshan Mountains area reveals that the sedimentary rocks in the Badaowan Fm.were sourced predominantly from the central and subordinately from the southern Tianshan Mountains during Early Jurassic.
基金Financial support for this work,provided by the National Basic Research Program of China(No.2006 CB202300),
文摘In order to determine the planar and volume distribution of sand bodies of the Jurassic Badaowan formation in Block T13 of Junggar basin,we used analysis of field outcrop and 3D seismic data,which play an essential role in areas of sparse well coverage.We describe sedimentary facies characteristics,sand body planforms,width and connectivity patterns of sand bodies,and vertical associations and successions by acoustic impedance inversion technology and sedimentological theory.Results of our study show braided fluvial strata deposits in the Jurassic Badaowan formation.Each sand body is approximately lenticular in shape.The width of each sand body falls in the range 100～800 m,with most between 200 and 400 m.The sand bodies vary in thickness from 4 to 13 m,with most below 9 m.The width/thickness ratios lie in the range 20～55.The connectivity of braided fluvial channel sand bodies is controlled by changes of accommodation space.One fining-upward sedimentary cycle of base-level rise is recognized in Badaowan formation,representing an upward rise of base level.The connectivity of sand bodies was found to be greatest in the early stage of base-level rise,becoming progressively worse with increasing base-level rise.
