摘要
渤海湾沉积记录研究对于认识华北平原形成过程及晚新生代以来东亚季风演化具有重要意义.对渤海湾G4孔~5.2 Ma以来的沉积物开展了粒度、色度及元素地球化学研究.结果表明:CIA、Al/Si、Al/Na、Al/K、Ba/Sr及(La/Sm)N、(La/Yb)N元素地球化学指标揭示钻孔底部5.2 Ma至1.6 Ma沉积物的化学风化程度由中等风化向弱风化转变,反映晚新生代全球气候变冷和东亚冬季风对华北平原产生同步影响. 1.60 Ma以来G4孔沉积物出现(La/Sm)N、(La/Yb)N明显增大, CIA、Al/Si、Al/Na、Al/K、Ba/Sr变化趋势与同期深海氧同位素、黄土CIA及87Sr/86Sr缓慢降低特征不相符的情况,指示发生了一次物源变化,可能与黄河进入华北平原有关.渤海湾钻孔剖面显示自1.60 Ma开始至0.78 Ma,黄骅坳陷被快速填平补齐,可能揭示黄河带来的大量物质对华北平原形成贡献巨大.
In this study, the grain size, chromaticity and elemental geochemistry of sediments from borehole G4 reaching Pliocene of Bohai Bay have been analyzed, and the sedimentary features and weathering degree of the sediments from this borehole since ~5.2 Ma have been expounded.The results showed that the ratios of CIA（chemical index of alteration）, Al/Si, Al/Na, Al/K, Ba/Sr and（La/Sm）N、（La/Yb）Nwere good indicators of weathering degree and material composition of sediments in North China. The grain size composition, chromaticity change and element ratio characteristics revealed that the chemical weathering degree of the sediments from ~5.2 Ma to 1.6 Ma changed from medium to weak, which revealed the synchronous effect caused by Late Cenozoic global cooling and the East Asian winter monsoon. Since 1.6 Ma, the（La/Sm）N、（La/Yb）Nfrom G4 hole have suddenly increased, and the trends of other indicators are not consistent with the slow decreasing characteristics of the deep ocean oxygen isotope ratio, the CIA and87 Sr/86 Sr of loess, indicating the change of sediment source. Considering the regional tectonic and climatic conditions, we assume that the change of sediment source from G4 since 1.6 Ma is related to the entry of Yellow River into the North China Plain at 1.6 Ma, and the Yellow River eventually cut through the Sanmen Gorge and enter the North China Plain with the dynamic of intensive headward erosion caused by globe climate changes in the early Pleistocene. The combined section of boreholes from Bohai Bay revealed that the Huanghua depression was basically filled, and the peneplanation process of the North China Plain mainly completed from 1.6 Ma to 0.78 Ma, which indicated that the great mass of sediments from Yellow River made a huge contribution in the forming of the North China Plain.
作者
杨吉龙
胥勤勉
胡云壮
袁海帆
王福
田立柱
肖国桥
Yang Jilong;Xu Qinmian;Hu Yunzhuang;Yuan Haifan;Wang Fu;Tian Lizhu;Xiao Guoqiao(Tianjin Centre,China Geological Survey,Tianjin 300170,China;Key Laboratory of Muddy Coast Geo-environment,China Geological Survey,Tianjin 300170,China;State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Wuhan 430074)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2018年第A01期287-300,共14页
Earth Science
基金
国家自然科学青年基金(No.41602205)
中国地质调查局项目(Nos.121201006000150009
121201006000182401)
关键词
渤海湾
上新世
风化过程
沉积演化
物源
地球化学
Bohai bay
Pliocene
chemical weathering
sedimentary evolution
provenance
geochemistry.
作者简介
杨吉龙（1980-），男，硕士，高级工程师，从事水文地质与第四纪地质研究．ORCID：0000-0002-5123-7011．E-mail：jilong．y@163．com
