Lacustrine sediments serve as valuable archives of extreme events and past environmental changes.However,the formation mechanisms and distribution patterns of gravity flow deposits in inland hypersaline lakes under cl...Lacustrine sediments serve as valuable archives of extreme events and past environmental changes.However,the formation mechanisms and distribution patterns of gravity flow deposits in inland hypersaline lakes under climatic controls remain underexplored.In the Eocene Jianghan Basin,rhythmic strata influenced by climatic cycles provide a unique opportunity to investigate the relationship between gravity flow deposits and paleoclimate.According to core descriptions,thin section analysis,logging data,and grain size analysis,seven lithofacies and four lithofacies associations related to gravity flow deposits were identified.Frequent turbidity flows,primarily flood-induced gravity flows,are widely distributed in the saline lake.Proximal gravity flow deposits are characterized by thick,massive sandstones with minimal mud debris,occasionally featuring deformed lamination and scoured bases.Distal gravity flow deposits comprise clast-bearing massive sandstones,planar laminated sandstones,and graded siltstones.Paleoclimate analysis,based on trace elements and rock salt thickness,reveals a strong linkage between gravity flow deposits and climatic cycles.Correlations were established by systematically identifying short-term base-level cycles,which were subsequently grouped into medium-term base-level cycles through stacking pattern analysis.Short-term base-level changes,corresponding to stable climatic cycles,are marked by rhythmic salt layers.In contrast,medium-term base-level cycles,controlled by orbital periods,govern the deposition of gravity flow deposits.Under arid climatic conditions,reduced vegetation coverage and pronounced temperature variations lead to intensified erosion and increased suspended particle concentration.The deposition of sandstone layers is more substantial,and the frequency of turbidity flows is significantly higher under arid climatic conditions compared to humid climatic conditions.This research highlights how climatic cycles influence gravity flow deposits in hypersaline lake environments.展开更多
Two rectangular-shaped lakes,Lake Hulun and Lake Buir,located at the boundary between China and Mongolia,only c.75 km apart and therefore experiencing similar wind fields,have been studied based on satellite images an...Two rectangular-shaped lakes,Lake Hulun and Lake Buir,located at the boundary between China and Mongolia,only c.75 km apart and therefore experiencing similar wind fields,have been studied based on satellite images and field surveys in order to compare their geomorphological and sedimentological characteristics.The wind-driven hydrodynamics,which have a significant effect on the development of littoral landforms and on sediment distribution,have been discussed for the two similar lakes that experienced a prevailing wind perpendicular to their long axis.A conceptual model related to wind-driven water bodies and sediment distribution is proposed.Wave-influenced to wave-dominated deltas,beaches,spits,and eolian dune deposits develop around these two lakes,with a strikingly similar distribution pattern.These features locally inform the longshore drift and help reconstruct the water circulation induced by wind forcing.Under the NW prevailing wind regime,the spits developed on the SW coast with a NW—SE extension,which was influenced by the NW—SE longshore currents.The same influence was observed in the delta extension in the NE area.The differences lie in the presence of fan deltas in the NW region of Lake Hulun,but not in Lake Buir.Additionally,the width of the beach and eolian deposits on the downwind coast of Lake Hulun is three times greater than that of Lake Buir which were caused by the differences in sediment supply and wind fetch between the two lakes.Lake Hulun and Lake Buir provide two reliable examples to understand the relationship among the wind field,provenance,hydrodynamics,landforms,and asymmetrical distribution of clastics in elongated lakes.They also represent relevant modern analogs,which may also be of guiding significance to wind-driven sand body prediction in lacustrine basins.展开更多
基金supported by the National Major Research Program for Science and Technology of China(Grant No.2017ZX05009-002)the National Natural Science Foundation of China(42402114)the Special Fund for Basic Scientific Research Operating Expenses of Central Universities(2652022035)。
文摘Lacustrine sediments serve as valuable archives of extreme events and past environmental changes.However,the formation mechanisms and distribution patterns of gravity flow deposits in inland hypersaline lakes under climatic controls remain underexplored.In the Eocene Jianghan Basin,rhythmic strata influenced by climatic cycles provide a unique opportunity to investigate the relationship between gravity flow deposits and paleoclimate.According to core descriptions,thin section analysis,logging data,and grain size analysis,seven lithofacies and four lithofacies associations related to gravity flow deposits were identified.Frequent turbidity flows,primarily flood-induced gravity flows,are widely distributed in the saline lake.Proximal gravity flow deposits are characterized by thick,massive sandstones with minimal mud debris,occasionally featuring deformed lamination and scoured bases.Distal gravity flow deposits comprise clast-bearing massive sandstones,planar laminated sandstones,and graded siltstones.Paleoclimate analysis,based on trace elements and rock salt thickness,reveals a strong linkage between gravity flow deposits and climatic cycles.Correlations were established by systematically identifying short-term base-level cycles,which were subsequently grouped into medium-term base-level cycles through stacking pattern analysis.Short-term base-level changes,corresponding to stable climatic cycles,are marked by rhythmic salt layers.In contrast,medium-term base-level cycles,controlled by orbital periods,govern the deposition of gravity flow deposits.Under arid climatic conditions,reduced vegetation coverage and pronounced temperature variations lead to intensified erosion and increased suspended particle concentration.The deposition of sandstone layers is more substantial,and the frequency of turbidity flows is significantly higher under arid climatic conditions compared to humid climatic conditions.This research highlights how climatic cycles influence gravity flow deposits in hypersaline lake environments.
基金supported by the National Science and Technology Special Project(No.2017ZX05009-002)the Fundamental Research Funds for the Central Universitiessupported by CNES through the funding of his postdoctoral fellowship。
文摘Two rectangular-shaped lakes,Lake Hulun and Lake Buir,located at the boundary between China and Mongolia,only c.75 km apart and therefore experiencing similar wind fields,have been studied based on satellite images and field surveys in order to compare their geomorphological and sedimentological characteristics.The wind-driven hydrodynamics,which have a significant effect on the development of littoral landforms and on sediment distribution,have been discussed for the two similar lakes that experienced a prevailing wind perpendicular to their long axis.A conceptual model related to wind-driven water bodies and sediment distribution is proposed.Wave-influenced to wave-dominated deltas,beaches,spits,and eolian dune deposits develop around these two lakes,with a strikingly similar distribution pattern.These features locally inform the longshore drift and help reconstruct the water circulation induced by wind forcing.Under the NW prevailing wind regime,the spits developed on the SW coast with a NW—SE extension,which was influenced by the NW—SE longshore currents.The same influence was observed in the delta extension in the NE area.The differences lie in the presence of fan deltas in the NW region of Lake Hulun,but not in Lake Buir.Additionally,the width of the beach and eolian deposits on the downwind coast of Lake Hulun is three times greater than that of Lake Buir which were caused by the differences in sediment supply and wind fetch between the two lakes.Lake Hulun and Lake Buir provide two reliable examples to understand the relationship among the wind field,provenance,hydrodynamics,landforms,and asymmetrical distribution of clastics in elongated lakes.They also represent relevant modern analogs,which may also be of guiding significance to wind-driven sand body prediction in lacustrine basins.
