Glacial–interglacial cycles in Sr and Nd isotopic composition of Arctic marine sediments triggered by the Svalbard/Barents Sea ice sheet
Glacial–interglacial cycles in Sr and Nd isotopic composition of Arctic marine sediments triggered by the Svalbard/Barents Sea ice sheet
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DOI：
10.1016/s0025-3227(01)00248-1
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发表时间：
2002-04
期刊：
影响因子：
2.9
通讯作者：
T. Tütken;A. Eisenhauer;Bettina A. Wiegand;B. T. Hansen
中科院分区：
文献类型：
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作者：
T. Tütken;A. Eisenhauer;Bettina A. Wiegand;B. T. Hansen
北极海洋沉积物Sr和Nd同位素组成特征的变化，沉积物源区和跟踪陆架-海洋颗粒路径在冰-间冰期转换在北冰洋东部。在斯瓦尔巴特群岛北部耶尔马克高原的一个140-ka海相岩心沉积记录中，87 Sr/86 Sr比值和ε Nd值分别在0.717和0.740之间以及-9.3和-14.9之间变化。Sr和Nd同位素组成的变化特征在冰期-间冰期旋回，并与斯瓦尔巴特/巴伦支海冰盖（SBIS）的延伸。Sr和Nd同位素组成的下芯变化表明，气候引起的变化，沉积物的来源从两个同位素不同的端员：（1）欧亚大陆架沉积物作为远源;和（2）斯瓦尔巴特群岛基岩作为近源，符合从海冰到冰川冰的运输机制的变化。在斯瓦尔巴冰川推进和冰川基岩侵蚀加剧的过程中，由于结晶斯瓦尔巴基岩物质的输入增加，ε Nd值逐渐下降到最小值-14.9。在冰川极大期，SBIS覆盖了整个巴伦支海大陆架，并提供了越来越多的欧亚大陆架材料的北冰洋冰筏碎屑（IRD）。冰川沉积物中的ε Nd值达到最大值，与现代欧亚大陆架和海冰沉积物的平均值（εNd=−10.3）相当。这证实了冰漂流是欧亚大陆架沉积物进入北冰洋的主要沉积物运输机制，并追踪了喀拉海/拉普捷夫海大陆架地区的沉积物来源。在基于陆架的SBIS衰减之后，冰川终止I（εNd=−10.6）和II（εNd=−10.1）期间的冰架沉积物峰值ε Nd值迅速下降到间冰期平均值的典型值−12.5。下钻芯Sr同位素组成与Nd同位素组成密切相关，但也可能受到粒度效应的影响。相反，一个整体沉积物样品的粘土-粉砂粒度级的Nd同位素组成类似于0.3-0.8 ε Nd单位，似乎是一个粒度独立的物源示踪剂。
Sr and Nd isotopic compositions of Arctic marine sediments characterize changes of sediment source regions and trace shelf–ocean particle pathways during glacial–interglacial transitions in the eastern Arctic Ocean. In the 140-ka sedimentary record of a marine core from Yermak Plateau, north of Svalbard,87Sr/86Sr ratios and εNdvalues vary between 0.717 and 0.740 and −9.3 and −14.9, respectively. Sr and Nd isotopic composition both change characteristically during glacial–interglacial cycles and are correlated with the extension of the Svalbard/Barents Sea ice sheet (SBIS). The downcore variation in Sr and Nd isotopic composition indicates climatically induced changes in sediment provenance from two isotopically distinct end-members: (1) Eurasian shelf sediments as a distal source; and (2) Svalbard bedrock as a proximal source that coincide with a change in transport mechanism from sea ice to glacial ice. During glacier advance from Svalbard and intensified glacial bedrock erosion, εNdvalues decrease gradually to a minimum value of −14.9 due to increased input of crystalline Svalbard bedrock material. During glacial maxima, the SBIS covered the entire Barents Sea shelf and supplied increasing amounts of Eurasian shelf material to the Arctic Ocean as ice rafted detritus (IRD). εNdvalues in glacial sediments reach maximum values that are comparable to the average value of modern Eurasian shelf and sea ice sediments (εNd=−10.3). This confirms ice rafting as a major sediment transport mechanism for Eurasian shelf sediments into the Arctic Ocean and trace a sediment origin from the Kara Sea/Laptev Sea shelf area. After the decay of the shelf-based SBIS, the glacial shelf sediment spikes during glacial terminations I (εNd=−10.6) and II (εNd=−10.1) εNdvalues rapidly decrease to values of −12.5 typical for interglacial averages. The downcore Sr isotopic composition is anticorrelated to the Nd isotopic composition, but may be also influenced by grain-size effects. In contrast, the Nd isotopic composition in clay- to silt-size fractions of one bulk sediment sample is similar to within 0.3–0.8 εNdunits and seems to be a grain-size independent provenance tracer.