海洋地质前沿2025，Vol.41Issue(4)：47-59,13.DOI:10.16028/j.1009-2722.2025.039
长江口外砂泥过渡带沉积粗化趋势与成因分析
Sediment coarsening trend and genetic analysis of the sandy-muddy transitional zone off the Yangtze River Estuary
摘要
Abstract
A narrow sandy-muddy transitional zone exists offshore the Yangtze River Estuary,separating the muddy subaqueous delta from the sandy East China Sea shelf,which is highly sensitive to the changes in fluvial sediment supply and marine hydrodynamic dynamics.We investigated decadal-scale changes in surface sediment grain size offshore the estuary and examined two sediment cores in YE 16 site collected in two consecutive years from the transitional zone,focusing on grain size,elemental ratios,organic compositions,and radionuclides.Res-ults reveal a recent landward migration of the outer boundary of the transitional zone,obvious surface sediment coarsening,and rapid thickening of sandy layers overlying muddy deposits in YE 16 site.Grain-size end-member(EM)analysis via the grain size-standard deviation method and component partitioning identified a pronounced increase in EM3(medium-fine sand end-member)in YE 16 cores.Sediments dominated by EM3 display lower C/N ratios,elevated Sr/Ba and Ca/Ti ratios,and depleted excess 210Pb and 137Cs activities,indicating older proven-ance with marine biogenic dominance.Integrated analysis attributes the EM3 increase to resuspension and on-shore transport of relict mid-shelf sandy sediments driven by high-energy events(e.g.,storm waves).This mech-anism of exogenic inputcoupled with drastic reductions in Yangtze-derived sediment,forms a dual driver for coarsening:exogenic sand compensates coarse fractions directly,while diminished fine sediment supply weakens the dilution effects.These combined processes explain recent landward migration,surface coarsening,and sandy layer thickening.Against intensifying extreme climatic events and watershed human activities,ongoing monitor-ing of the transitional zone's evolution and environmental impacts is imperative.关键词
砂泥过渡带/沉积物粗化/粒度端元分析/流域人类活动影响/强风浪Key words
sandy-muddy transitional zone/sediment coarsening/grain-size end-member analysis/watershed an-thropogenic disturbance/high-energy storm wave events分类
海洋学引用本文复制引用
黄雨菡,范代读,吴伊婧..长江口外砂泥过渡带沉积粗化趋势与成因分析[J].海洋地质前沿,2025,41(4):47-59,13.基金项目
国家自然科学基金(42330411) （42330411）
上海市教委科研创新计划自然科学重大项目(2021-01-07-00-07-E00093) （2021-01-07-00-07-E00093）
亚洲合作资金项目"长江三角洲与红河三角洲海洋地质环境与灾害合作研究" （）
