中国东部渤海湾晚中新世以来化学风化记录及地质意义  

Late Miocene geochemical weathering records and significances in the Bohai Bay,eastern China

作　　者：杨吉龙 张超宇 胥勤勉 胡云壮 周新郢[4] 肖国桥[5] YANG Jilong;ZHANG Chaoyu;XU Qinmian;HU Yunzhuang;ZHOU Xinying;XIAO Guoqiao(Tianjin Center,China Geological Survey(North China Center for Geoscience Innovation),Tianjin 300170,China;Tianjin Key Laboratory of Coast Geological Processes and Environmental Safety,Tianjin 300170,China;Chinese Academy of Natural Resources Economics,Beijing 101149,China;Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences,Institute of Vertebrate Paleontology and Paleoanthropology,Beijing 100044,China;School of Geography and Information Engineering,University of Geosciences,Wuhan,Hubei 430074,China)

机构地区：[1]中国地质调查局天津地质调查中心(华北地质科技创新中心),天津300170 [2]天津市海岸带地质过程与环境安全重点实验室,天津300170 [3]中国自然资源经济研究院,北京101149 [4]脊椎动物演化与人类起源重点实验室/中国科学院古脊椎动物与古人类研究所,北京100044 [5]中国地质大学(武汉)地理与信息工程学院,湖北武汉430074

出　　处：《地质学报》2025年第3期976-990,共15页Acta Geologica Sinica

基　　金：国家自然科学基金面上项目(编号41972196);中国地质调查项目(编号DD20230091)联合资助的成果。

摘　　要：渤海湾西岸位于中国东部边缘海,晚新生代主要为湖相、河流相及海相沉积,厚度达数千米,是研究晚新生代古气候演变、海平面变化及区域构造活动的理想场地。本次研究对渤海湾西岸晚中新世以来的两个深孔进行了元素地球化学和黏土矿物分析。结果表明CIA、Al/Na、Al/K和Al/Si比值对中国东部沉积物风化程度有较好的指示作用,8.5~3.6 Ma之间风化程度较高,大致与孢粉记录揭示的暖湿气候一致;3.6 Ma以来因极地冰量增加,东亚冬季风增强,导致沉积物风化程度逐渐降低。1.5 Ma以来两个钻孔沉积物CIA值、Al/Si、Al/Na和Al/K比值较低且变化幅度较小,与深海氧同位素、黄土的CIA值表现的缓慢降低特征不相符,可能指示了物源的变化,推测与黄河携带大量物质进入华北平原有关。早更新世中期黄河贯通进入华北平原的动力机制可能是构造运动叠加来自气候变化条件下的溯源侵蚀。The thick alluvial,lacustrine,and marine sediments deposited in the Bohai Sea coastal plain hold valuable information about Cenozoic climate change,global sea-level fluctuations,sediment provenance,and regional tectonics.However,reconstructing long-term paleoenvironmental changes in this area has been hindered by the scarcity of well-dated,deep sediment cores.In this study,we present geochemical and palaeobotanical records from two well-dated boreholes(G2:1226 m and G3:905 m)that extend back to the late Miocene in the Bohai Sea coastal plain.Our results indicate that the CIA and ratios of Al/Na,Al/K,and Al/Si are good indicators for the degree of chemical weathering.Intense chemical weathering is observed between 8.5 Ma and 3.6 Ma,coinciding with a relatively warm and humid climate as revealed by sporopollen records from the G2 borehole.Since 3.6 Ma,a decrease in chemical weathering intensity and an increase in conifers in the palynological assemblages indicate a gradual cooling trend,consistent with ongoing high-latitude cooling and the strengthening of the East Asian winter monsoon during this interval.A sharp decline in chemical weathering intensity is observed since~1.5 Ma,deviating from the gradual trends observed in deep-seaδ^(18)O records and loess CIA values.This discrepancy is attributed to the influx of dry and cold climate-derived sediments from the Loess Plateau into Bohai Bay,leading to reduced chemical weathering intensity.This interpretation is supported by our previous detrital zircon provenance analysis,which revealed a shift in sediment sources around 1.5 Ma.We propose that tectonic movements,coupled with persistent dry and cold conditions,lowered the regional water level datum and intensified headward erosion in North China since~1.5 Ma.This provided the driving force for the Yellow River to incise through the Sanmen Gorge and enter the North China Plain,contributing eroded loess material to the Bohai Sea coastal plain.

关 键 词：渤海湾 晚中新世 化学风化 古气候 物源 

分 类 号：P61[天文地球—矿床学]