The differences in sedimentary filling within a continental lacustrine basin,caused by lake-level fluctuations,pose significant impacts on hydrocarbon generation and enrichment,while the lake-level fluctuations are notably influenced by climatic changes.In this study,we investigate the continuous lacustrine sedimentary records preserved in the 1st member of the Shaximiao Formation(also referred to as the Sha 1 Member)of the early Middle Jurassic in the central Sichuan Basin.Using the high-resolution natural gamma-ray(GR)log data as paleoclimate proxies,we explore the cyclostratigraphy of the early Middle Jurassic continental strata.Through the filtering of long and short eccentricity cycles,we establish a floating astronomical time scale(ATS)for the Sha 1 Member.The results indicate that the sedimentary strata in the lacustrine basin of the Sha 1 Member preserve well-defined response signals to astronomical cycles.Calculations by the ATS reveal that the Sha 1 Member in the central Sichuan Basin underwent continuous deposition for approximately 2.43 Ma.The combination of eccentricity maxima and relatively high precession amplitude suggests a warm and humid climate.In this case,the lake level rose relatively,resulting in the development of argillaceous sediment.In contrast,the combination of eccentricity minima and relatively low precession amplitude implies a cold and arid climate.In this case,sandy sediment occurred,the thickness of which is modulated by precession amplitude.The driving forces of the orbital cycles at different scales during the early Middle Jurassic jointly determined the climatic changes,which caused lake-level fluctuations and further affected the sediment distribution.
关键词
湖平面波动/气候变化/旋回地层学/沉积物分布规律/沙溪庙组一段/中侏罗世/陆相湖盆/四川盆地
Key words
lake-level fluctuation/climatic change/cyclostratigraphy/sediment distribution pattern/the 1st member of the Shaximiao Formation(Sha 1 Member)/Middle Jurassic/continental lacustrine basin/Sichuan Basin
维普
万方数据