末次盛冰期以来冰岛南部陆坡沉积物来源变化及其对周边冰盖消涨的响应

Changes in sediment sources in the southern slope of Iceland since the Last Glacial Maximum and their response to the adjacent ice sheets

  • 摘要: 冰岛南部陆坡岩芯沉积物记录的末次盛冰期以来海洋沉积物来源可以反映千年尺度的冰盖及洋流变化。本文利用冰岛南部陆坡ARC05/IS-2A岩芯沉积物浮游有孔虫AMS14C测年数据构建年代框架,并进行了粒度、颜色反射率以及高分辨率X射线荧光光谱仪元素地球化学测试。根据X射线荧光光谱仪分析结果,通过因子分析方法确定了IS-2A岩芯沉积物的主要物质来源;结合前人对冰盖及洋流变化的研究,重建了末次盛冰期以来冰岛南部陆坡沉积物来源的演化过程,讨论了沉积物来源变化及其与周边主要冰盖活动之间的关系。结果表明,末次盛冰期以来IS-2A岩芯沉积物以陆源输入为主。 其中,末次盛冰期研究区碎屑沉积物主要来自冰岛冰盖、不列颠-爱尔兰冰盖和斯堪的纳维亚冰盖。而在末次冰消期初期,陆源碎屑物质整体增加,它们主要来自近源冰岛冰盖、斯堪的纳维亚冰盖和不列颠-爱尔兰冰盖,以及远端劳伦德冰盖。末次冰消期中后期,由于搬运条件的减弱,劳伦德冰盖的陆源输入有所减少,反映了冰盖活动对研究区沉积物来源的制约。进入全新世后,现代洋流体系形成,在冰岛-苏格兰溢流水和北大西洋暖流的共同作用下,沉积物主要来自冰岛和欧洲西部,拉布拉多半岛的碎屑物质也有部分输入。

     

    Abstract: Changes of marine sedimentary environment since the Last Glacial Maximum (LGM) recorded in the core sediments of the southern slope of Iceland reflect millennial-scale changes in ice sheets and ocean currents. The age framework was established with AMS14C dating data of the ARC05/IS-2A core sediments in the southern slope of Iceland, and the grain size, color reflectance and high-resolution XRF element geochemical tests were carried out. According to the XRF spectrometer analysis results, the main material source of the IS-2A core sediment was determined through factor analysis method. Combined with previous studies on the changes of ice sheets and ocean currents in North Atlantic, the evolution of sediment sources on the southern slope of Iceland since the LGM was reconstructed, and the relationship between the changes of sediment sources and activities of the surrounding major ice sheets was discussed. Results show that the sediments of IS-2A core are mainly terrigenous since the LGM. Detritus in sediment indicate the main source areas from the Iceland Ice Sheet (IIS), the British-Irish Ice Sheet (BIIS), and the Finnoscandia Ice Sheet (FIS). In the early last deglaciation, terrigenous detritus were increased as a whole, came mainly from IIS, FIS and BIIS, as well as the distal Laurent ice sheet (LIS). In the middle and late period of the last deglaciation, due to the weakening of transport conditions, the terrestrial input of LIS decreased, reflecting the restriction of ice sheet on the sediments supply to the study area. In the Holocene, the modern ocean current system was formed. Under the combined action of the Iceland-Scotland Overflow Water and the North Atlantic Current, sediments mainly came from Iceland and western Europe, and partially from the detritus of the Labrador Peninsula.

     

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