Sedimentary Characteristics And Cyclostratigraphic Division Of The Qiancengya Section In The Early Cretaceous In The Lingshan Island

Deep-water deposition is one of the most important sediments transport methods on the earth,and it is rich of oil and gas.However,the sedimentary characteristics of deep-water are complex and changeable due to the diversity of deep-water fluids.In order to study the sedimentary characteristics and the vertical stratigraphic cycles of deep-water,we selected the Early Cretaceous deep-water sedimentation in Lingshan Island,Qingdao,Shandong Province as research object.Based on outcrop observations,core observations,microscopic section,X-ray fluorescence analysis,scanning electron microscopy and core gamma scanning observations,the grain size structures,sedimentary characterastics were studied.The grain size of study area is fine and the composition of rock varies a bit.There are grain sequence bedding and various slump deformation structures in study area.According to the differences in sedimentary grain size,shale content and sedimentary structure in the study area,we divided the lithofacies.The lithofacies in the study area were first divided into sandstone,siltstone and argillaceous siltstones.Based on sedimentary structures and inclusions,the litofacies were further subdivided into positively-transforming(siltstone)sandstones,anti-graded(siltstone)sandstones,massive bedding(siltstone)sandstone facies,parallels bedding(siltstone)sandstone facies,staggered bedding sandstone facies,detrital(siltstone)sandstone facies,detrital argillaceous siltstone facies,massive argillaceous siltstone facies,horizontal bedding shale facies,massive bedding shale facies.According to the regular combination of lithofacies type,rock thickness,internal structure,and external morphology in the vertical direction,six types of lithofacies combinations are classified.Through 1:1 sketching of the entire section,it is found that the combination of lithofacies in the study area is complex and changeable.From the bottom up,the shale content is reduced and the massive sandstone facies is increased.It is believed that the sedimention of bottom cliff is mainly turbidite sedimention and hybrid sedimentation,the deposition of top profile is mainly debris flow deposit.The paleo-climate,paleo-water depth,paleo-salinity,and terrestrial input were recovered with geochemical parameters,and the profile was divided into five stages based on the geochemical parameters in the vertical,which dominated by paleoclimate.Based on GR logging combined with the combination of lithofacies,the profile is divided into 15 "GRP" cycles.Study suggests that the “GRP” cycle is controlled by the input of terrestrial sources.According to the combination of the vertical lithofacies of the profile,the profile is divided into 47 cycles and the sedimentation is from bottom to top is: turbidite deposition ? hybrid sedimentation ? clastic flow deposition.Lithofacies cycle is controlled by deposition events.There are better couplings between cycles of different scales.The climate cycle scale is larger,and contains 2 to 3 types of sedimentation in cycle.The terrestrial input cycle contains generally two kinds sedimentation.The lithofacies cycle one deposition.The deposition of the profile from the bottom to the top changes frequently and spirally.This study is important for understanding and understanding the complexity of deepwater gravity flow sedimentation...