Shales in deep lake basins have become the main focus of continental shale oil and gas exploration.In order to highlight the sedimentary dynamics of mud deposition in deep lake basins,a combination of core observation...Shales in deep lake basins have become the main focus of continental shale oil and gas exploration.In order to highlight the sedimentary dynamics of mud deposition in deep lake basins,a combination of core observation,thin section examination,X-ray diffraction,and QEMSCAN(quantitative evaluation of minerals by scanning electron microscopy)was used to analyze the depositional characteristics of mudrocks in the Chang-7 Member from the Yanchang Formation(Upper Triassic)in Ordos Basin,and to establish a depositional model for mud accumulation in deep lake basins.This study recognizes four mudrock lithofacies in the Chang-7 Member:(1)the laminated silt-bearing mudstone,which generally develops a binary composition of“silt-clay”or a ternary composition of“silt-clay-organic matter”;(2)the graded mudstone,mainly composed of dark gray and gray-black mudstone sandwiched by silt-bearing mudstone;(3)the massive mudstone,internally showing a uniform distribution of quartz,clay,and carbonate minerals,with also a small amount of organic detritus;and(4)the laminated shale,which is generally composed of clay laminae,and organic laminae of the former two.Sediment supply,topographic slope,and flood intensity combine to control the evolution of gravity flows and the transport and deposition of the mudrock in the Chang-7 Member.The influence of orogeny provides terrain gradient,water depth,abundant sediments at source areas,and triggering mechanism for the formation of gravity flows.Floods triggered by wetting events provide the impetus for sediment transport.Mud deposition in the Chang-7 Member was mainly related to the transport and sedimentation of mud by hyperpycnal flows and rapid sedimentation by buoyant plume flocculation.A comprehensive evolutionary model for shale accumulation in the deep lake basin is established by integrating various triggering mechanisms and mud transport sedimentary processes.展开更多
Based on the abundant information from drilling, cores, and logging, the influence of topography, size of rivers and lakes, climate changes and the lake level＇s fluctuation on the sandbodies at shallow-water delta fr...Based on the abundant information from drilling, cores, and logging, the influence of topography, size of rivers and lakes, climate changes and the lake level＇s fluctuation on the sandbodies at shallow-water delta front are systematically summarized and the sedimentary dynamic processes are analyzed. The interwell communication among the sandbodies and their planar distribution revealed from the hydrodynamic features of the development wells are integrated during the analysis. The fundamental requirements for the development of the shallow-water delta included flat topography and uniform subsiding rate. The delta plain was connected smoothly with the wide delta front and predelta, without the three-fold structure of topset, foreset, and bottomset as defined in the Gilbert Delta Model. Because of the weak fluvial effect and the lake energy is strong, the small and scattered shallow-water delta is destroyed by the scouring-backwashing, coastal current, and lake wave, resulting in the coastal sheet deposition. As the fluvial effect became stronger and the lake energy became weaker, the shape of the shallow-water deltas transferred from sheets to lumps and then branches.展开更多
The grain-size distribution of surface sediments in the Bohai Sea(BS) and the northern Yellow Sea(NYS), and its relationship with sediment supply and hydrodynamic environment were investigated based on grain-size comp...The grain-size distribution of surface sediments in the Bohai Sea(BS) and the northern Yellow Sea(NYS), and its relationship with sediment supply and hydrodynamic environment were investigated based on grain-size compositions of surface sediments and modern sedimentation rates. The results showed that the surface sediments in the BS and the NYS were primarily composed of silty sand and clayey silt with a dominant size of silt. In addition, the Yellow River delivered high amount of water and sediments to the BS, and they are dominated in surface sediments(mainly silt) in the Bohai Bay, the Yellow River mouth, the center of the BS, and the north coast of Shandong Peninsula. The coarse-grained sediments were mainly deposited at the river mouth due to the estuarine filtration and physical sorting. Meanwhile, there was a significant relationship among the modern sedimentation rate, the surface sediment grain size distribution and sediment transport pattern. The areas with coarser surface sediments generally corresponded low sedimentation rates because of strong erosion;whereas the sedimentation rate was relatively high at the place that the surface sediments were fine-grained. Furthermore, the grain-size trend analysis showed that the areas with fine-grained surface sediments such as the mud area in the central BS and the upper Liaodong Bay were the convergent centers of surface sediments, except for the Bohai Bay and the subaqueous Yellow River Delta where offshore sediment transport was evident.展开更多
Grain size analysis and chemical analysis of heavy metals are made for 312 surface samples of the Jiaozhou Bay. Nineteen samples of the waste water taken from the sewage discharge outlets along the eastern coast of th...Grain size analysis and chemical analysis of heavy metals are made for 312 surface samples of the Jiaozhou Bay. Nineteen samples of the waste water taken from the sewage discharge outlets along the eastern coast of the bay are also analyzed for heavy metals. Results show that heavy metals are richer in the east and poorer in the west of the bay. Sedimentary dynamic studies reveal that the distribution of heavy metals in the surface sediments of the Jiaozhou Bay is under the control of hydrodynamics.展开更多
With available survey data and 237surface sediment samples,the modern sedimentation in Qingdao bays is studied.The research result shows that the east area is shallower(16.4 m) than that in the west(45.8 m).The geogra...With available survey data and 237surface sediment samples,the modern sedimentation in Qingdao bays is studied.The research result shows that the east area is shallower(16.4 m) than that in the west(45.8 m).The geography was formed by a symmetric wave in a sequence of bank-offshore depression-platform-tidal channel-platform-offshore depression-foreshore from south to north.Flood sedimentary systems were formed from inlet of the Jiaozhou Bay in the west to the barrier bar in the east.Lateral sedimentation includes mainly tidal current ridges in two tidal channels.Gravel sandy sediments formed by wave lie in midland of from seashore to wave base.Dynamic functions are mainly tide and wave.Tidal current moves sediment in vertical and horizontal directions,sorting sediments and providing materials for coastwise beaches.The sources of sediment are mainly from eroded headland rocks.In general,grain sizes in this area from the inlet of the Jiaozhou Bay in the west(120°17') to the barrier bar outside in the east(120°35') are coarse-fine-coarse,forming gravel-gravelly sand(G-S),sand(S),gravel clay silt(G-YT),clay silt(YT),gravelly silty sand(G-TS),silty sand(TS),gravelly sandy silt(G-ST),and sandy silt(ST) in turn.展开更多
基金co-funded by the National Natural Science Foundation of China (Grant No.42372141and Grant No.42072126)Open Fund (DGERA20241002) of Key Laboratory of Deep-time Geography and Environment Reconstruction and Applications of Ministry of Natural Resources,Chengdu University of Technologythe Science Development Fund of Dongying (Grant No.2024kyqd004).
文摘Shales in deep lake basins have become the main focus of continental shale oil and gas exploration.In order to highlight the sedimentary dynamics of mud deposition in deep lake basins,a combination of core observation,thin section examination,X-ray diffraction,and QEMSCAN(quantitative evaluation of minerals by scanning electron microscopy)was used to analyze the depositional characteristics of mudrocks in the Chang-7 Member from the Yanchang Formation(Upper Triassic)in Ordos Basin,and to establish a depositional model for mud accumulation in deep lake basins.This study recognizes four mudrock lithofacies in the Chang-7 Member:(1)the laminated silt-bearing mudstone,which generally develops a binary composition of“silt-clay”or a ternary composition of“silt-clay-organic matter”;(2)the graded mudstone,mainly composed of dark gray and gray-black mudstone sandwiched by silt-bearing mudstone;(3)the massive mudstone,internally showing a uniform distribution of quartz,clay,and carbonate minerals,with also a small amount of organic detritus;and(4)the laminated shale,which is generally composed of clay laminae,and organic laminae of the former two.Sediment supply,topographic slope,and flood intensity combine to control the evolution of gravity flows and the transport and deposition of the mudrock in the Chang-7 Member.The influence of orogeny provides terrain gradient,water depth,abundant sediments at source areas,and triggering mechanism for the formation of gravity flows.Floods triggered by wetting events provide the impetus for sediment transport.Mud deposition in the Chang-7 Member was mainly related to the transport and sedimentation of mud by hyperpycnal flows and rapid sedimentation by buoyant plume flocculation.A comprehensive evolutionary model for shale accumulation in the deep lake basin is established by integrating various triggering mechanisms and mud transport sedimentary processes.
文摘Based on the abundant information from drilling, cores, and logging, the influence of topography, size of rivers and lakes, climate changes and the lake level＇s fluctuation on the sandbodies at shallow-water delta front are systematically summarized and the sedimentary dynamic processes are analyzed. The interwell communication among the sandbodies and their planar distribution revealed from the hydrodynamic features of the development wells are integrated during the analysis. The fundamental requirements for the development of the shallow-water delta included flat topography and uniform subsiding rate. The delta plain was connected smoothly with the wide delta front and predelta, without the three-fold structure of topset, foreset, and bottomset as defined in the Gilbert Delta Model. Because of the weak fluvial effect and the lake energy is strong, the small and scattered shallow-water delta is destroyed by the scouring-backwashing, coastal current, and lake wave, resulting in the coastal sheet deposition. As the fluvial effect became stronger and the lake energy became weaker, the shape of the shallow-water deltas transferred from sheets to lumps and then branches.
基金supported by the National Natural Science Foundation of China (No.41525021)the Ministry of Science and Technology of People's Republic of China (Nos.2016YFA0600903 and 2017YFC0405502)。
文摘The grain-size distribution of surface sediments in the Bohai Sea(BS) and the northern Yellow Sea(NYS), and its relationship with sediment supply and hydrodynamic environment were investigated based on grain-size compositions of surface sediments and modern sedimentation rates. The results showed that the surface sediments in the BS and the NYS were primarily composed of silty sand and clayey silt with a dominant size of silt. In addition, the Yellow River delivered high amount of water and sediments to the BS, and they are dominated in surface sediments(mainly silt) in the Bohai Bay, the Yellow River mouth, the center of the BS, and the north coast of Shandong Peninsula. The coarse-grained sediments were mainly deposited at the river mouth due to the estuarine filtration and physical sorting. Meanwhile, there was a significant relationship among the modern sedimentation rate, the surface sediment grain size distribution and sediment transport pattern. The areas with coarser surface sediments generally corresponded low sedimentation rates because of strong erosion;whereas the sedimentation rate was relatively high at the place that the surface sediments were fine-grained. Furthermore, the grain-size trend analysis showed that the areas with fine-grained surface sediments such as the mud area in the central BS and the upper Liaodong Bay were the convergent centers of surface sediments, except for the Bohai Bay and the subaqueous Yellow River Delta where offshore sediment transport was evident.
文摘Grain size analysis and chemical analysis of heavy metals are made for 312 surface samples of the Jiaozhou Bay. Nineteen samples of the waste water taken from the sewage discharge outlets along the eastern coast of the bay are also analyzed for heavy metals. Results show that heavy metals are richer in the east and poorer in the west of the bay. Sedimentary dynamic studies reveal that the distribution of heavy metals in the surface sediments of the Jiaozhou Bay is under the control of hydrodynamics.
基金Supported by the National Natural Scientific Foundation of China (No 40506013)
文摘With available survey data and 237surface sediment samples,the modern sedimentation in Qingdao bays is studied.The research result shows that the east area is shallower(16.4 m) than that in the west(45.8 m).The geography was formed by a symmetric wave in a sequence of bank-offshore depression-platform-tidal channel-platform-offshore depression-foreshore from south to north.Flood sedimentary systems were formed from inlet of the Jiaozhou Bay in the west to the barrier bar in the east.Lateral sedimentation includes mainly tidal current ridges in two tidal channels.Gravel sandy sediments formed by wave lie in midland of from seashore to wave base.Dynamic functions are mainly tide and wave.Tidal current moves sediment in vertical and horizontal directions,sorting sediments and providing materials for coastwise beaches.The sources of sediment are mainly from eroded headland rocks.In general,grain sizes in this area from the inlet of the Jiaozhou Bay in the west(120°17') to the barrier bar outside in the east(120°35') are coarse-fine-coarse,forming gravel-gravelly sand(G-S),sand(S),gravel clay silt(G-YT),clay silt(YT),gravelly silty sand(G-TS),silty sand(TS),gravelly sandy silt(G-ST),and sandy silt(ST) in turn.
