北极东西伯利亚陆架表层沉积物的岩石磁学特征及环境意义

Magnetic signatures and paleoenvironmental implications of surface sediments from the East Siberian Arctic Shelf

  • 摘要: 作为全球气候变化的“放大器”,北极对气候环境变化极为敏感,其沉积记录为认识高纬环境过程及全球气候系统演变提供了重要信息。本研究通过对北极东西伯利亚陆架91个站位的表层沉积物开展高、低频质量磁化率(χhfχlf)、频率磁化率(χfd)和非磁滞剩磁(ARM)等环境磁学分析,结合黏土矿物与地球化学数据资料,探讨了磁性矿物变化特征及其环境指示意义。结果表明,沉积物低频质量磁化率呈现显著的空间分异性,可划分为3个区域:拉普捷夫海东部与楚科奇海西部为高磁化率区,东西伯利亚海中部为低磁化率区。拉普捷夫海东部高磁化率区主要反映西伯利亚大火成岩省富含铁镁质矿物的基性火成岩物质输入,楚科奇海西部高磁化率区与鄂霍次克–楚科奇火山带的物质输入及白令海入流水携带的火山碎屑密切相关。东西伯利亚海中部的低磁化率区则反映物质主要来自科雷马河和因迪吉尔卡河流域的中酸性安山岩及花岗岩等弱磁性源区。χfd、ARM和χARM/χlf值在河口近岸普遍较低,表明磁性矿物粒度较粗;向中外陆架延伸上述磁学参数逐渐增高,显示细粒磁性矿物占优,上述变化反映出水动力变化及其导致的粗细粒物质发生分异的综合影响。除河流输入与环流作用外,海冰过程在沉积物搬运与再分配中也发挥了重要作用。东西伯利亚陆架表层沉积物的磁学参数综合记录了物源与水动力环境等多重过程,为理解北极陆架沉积体系的形成演化提供了重要手段。

     

    Abstract: As a key amplifier of global climate change, the Arctic is highly sensitive to climatic and environmental changes. Its sedimentary records provide important insights into high-latitude environmental processes and the evolution of the global climate system. This study presents the results of environmental magnetic analysis of surface sediments from 91 stations in the East Siberian Arctic Shelf. The mass-specific magnetic susceptibility (χ) at low and high frequencies, frequency-dependent magnetic susceptibility (χfd), and anhysteretic remanent magnetization (ARM) were analyzed in combination with clay mineralogy and geochemical data, from which the variations in magnetic mineral assemblages and their environmental significance were investigated. Results reveal a pronounced spatial heterogeneity in low-frequency mass-specific magnetic susceptibility (χlf) of the sediments, based on which three distinct provinces were divided: two high susceptibility provinces of the eastern Laptev Sea and western Chukchi Sea, and a low susceptibility province of the central East Siberian Sea. The high magnetic susceptibility reflects primarily the input of terrigenous detritus rich in mafic minerals derived from basic igneous rocks in the source areas. In contrast, the low susceptibility province corresponds to the source rocks with weaker magnetic intensities, such as granites and metamorphic rocks. Values of χfd, ARM, and their ratio (χARM/χ) are generally low in the estuarine and coastal areas, indicating the presence of coarser magnetic mineral grains. These parameters progressively increase towards the middle and outer shelf, signifying a dominance of fine-grained magnetic minerals. The observed variations reflect the combined effects of hydrodynamic changes and the resulting grain-size differentiation of sedimentary materials. In addition to fluvial input and ocean current processes, sea-ice dynamics also played a significant role in sediment transport and redistribution. The magnetic parameters of the East Siberian Shelf surface sediments integratively record multiple processes, including provenance and hydrodynamic conditions, thereby providing an important mean to understand the formation and evolution of the Arctic shelf sedimentary system.

     

/

返回文章
返回