渤海湾西北岸中更新世中期以来的气候环境和沉积环境演变

Evolution of the climate and sedimentary environment since the middle Pleistocene on the northwestern coast of the Bohai Bay

渤海湾西北岸是渤海湾沿岸砂坝-潟湖沉积体系组成部分,其沉积物蕴含着丰富的地质环境演变信息,是认识该地区气候环境和新构造活动的关键。通过对渤海湾西北岸QEJ01孔80m以上地层沉积环境、孢粉分析及微体古生物研究,结合测年数据,根据定量古气候重建数据,探讨了本区中更新世中期以来特征时期的植被演替及环境演变,并对MIS6~MIS1各阶段渤海湾西北岸的气候及环境变化进行了区域对比。QEJ01孔450.40~377.14ka,植被类型以针阔混交林为主,气候温暖干燥,沉积环境由河床逐渐演变为滨海湖泊;377.14~113.96 ka,气候相对寒凉湿润,植被类型以针阔叶混交林-草原为主,沉积环境以湖泊为主,后期为洪泛平原;113.96~98.84ka,该时期气候波动频繁,以稀树荒漠草原为主,气候温凉湿润,河床发育;98.84~74.33ka,气候温暖湿润,植被景观为针阔混交林-草原,降水量增加,沉积环境以漫滩湖泊和河床相为主;74.33~48.09ka,气候异常寒冷干旱,以针叶林为主的稀疏-荒漠草原较发育;48.09~25.72ka,植被类型为针阔混交林-草原,气候温暖偏湿;25.72~22.52ka,气候寒凉干旱,植被为稀树-荒漠草原;22.52~3.87ka,植被类型由常绿落叶阔叶林演变为针阔混交林-草原,气候温暖湿润,沉积环境以三角洲平原为主;3.87~0.0ka,气候凉爽干旱,植被类型以针阔混交林为主。渤海湾西北岸平原为构造活动的活跃地带,自MIS5阶段以来,沉降中心呈现自北西向南东迁移,以及海侵层的发育程度,均受区域构造运动和气候环境变化的影响控制。

The northwestern shore of the Bohai Bay is part of the sand bar-lagoon sedimentary system along the Bohai Bay.Its sediments contain rich information on the evolution of the geological environment,which is the key to understanding climate change and tectonism in this area.Based on the shallow stratigraphic sedimentary environment,sporopollen analysis and micropaleontological studies on the 80mthick sequence above the QEJ01 hole in the northwestern coast of the Bohai Bay,combined with chronological data and quantitative paleoclimate reconstruction data,the vegetation evolution in the characteristic period since the middle Pleistocene in this area is discussed.To reconstruct the environmental evolution,the regional comparisons of the climate and environmental changes in the northwestern coast of the Bohai Bay at each stage of MIS6~MIS1is carried out.In the QEJ01hole sequence,between 450.4~377.14ka,the vegetation type was mainly coniferous and broad-leaved mixed forest,the climate was warm and dry,and the sedimentary environment gradually evolved from a river bed to a coastal lake.From 377.14~113.96ka,the climate was relatively cold and humid,and the vegetation type was mainly coniferous and broad-leaved mixed forest-steppe.The sedimentary environment was dominated by lacustrine and the later period is flood plain.Between 113.96~98.84ka,the climate fluctuated frequently.It was mainly sparse tree desert grassland,the climate was cool and humid,the river bed was developed.From 98.84~74.33ka,the climate was warm and humid,the vegetation landscape was coniferous and broad-leaved mixed forest-grassland.Precipitation increased,the sedimentary environment was mainly floodplain lake and riverbed facies.Between 74.33~48.09ka,the climate was unusually cold and dry,and the sparse-desert forest was mainly coniferous forest.Grasslands were more developed.From 48.09~25.72ka,the vegetation type was coniferous and broadleaved mixed forest-grassland,the climate was warm and humid.Between 25.72~22.52ka,the climate was cold and dry,the vegetation was sparse tree-desert grassland.22.52~3.87ka,the vegetation type was evergreen deciduous broad-leaved forest that evolved into coniferous-broad mixed forest-grassland,with a warm and humid climate,and the sedimentary environment was mainly delta plain.Between 3.87~0.0ka,the climate was cool and dry,the vegetation type was mainly coniferous-broad mixed forest.The plain on the northwestern coast of the Bohai Bay is an active zone of tectonic activity.Since the MIS5stage,the subsidence center has migrated from northwest to southeast,and the degree of development of the transgressive layer is controlled by regional tectonic movements and changes in climate and environment.