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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Quartz content and the quartz-to-plagioclase ratio determined by X-ray diffraction: a proxy for ice rafting in the northern North Atlantic?
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Quartz content and the quartz-to-plagioclase ratio determined by X-ray diffraction: a proxy for ice rafting in the northern North Atlantic?

机译：通过X射线衍射确定的石英含量和石英与斜长石之比：是北大西洋北部漂流的代名词吗？

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摘要

Many paleoceanographic reconstructions of the glacial North Atlantic include estimates of iceberg discharge, which are based on the variable abundance of ice-rafted detritus (IRD) in deep-sea sediments. IRD abundance is most often determined by the mechanical separation and painstaking counting of terrigenous particles larger than a specified threshold grain size, typically 150 μm. Here we present a new proxy for IRD based on X-ray diffraction (XRD) analysis of bulk sediments. This approach complements results obtained from standard techniques while offering several distinct advantages. In addition to the rapid production of objective data, XRD measurements on bulk sediments are sensitive to a broader and more characteristic grain size range than counts of individual coarse lithic fragments. The technique is demonstrated in a study of 12 sediment cores from the North Atlantic. Bulk quartz content and the quartz-to-plagioclase ratio exhibit peak-to-peak correspondence to manual counting results, which verifies the identification of large IRD influxes. The XRD data also reveal variations between the manually identified peaks, suggesting increased sensitivity to low-level, distal, or sea-ice sources of IRD. A saw-tooth pattern emerges in many IRD events, which supports a link between ice rafting and atmospheric temperature changes over Greenland, and providing further evidence of the influence of climate on iceberg discharges.
机译：冰河北大西洋的许多古海洋重建都包括对冰山流量的估计，这些估计是基于深海沉积物中浮冰碎屑（IRD）的可变丰度而得出的。 IRD的丰度通常由大于特定阈值粒度（通常为150μm）的陆源颗粒的机械分离和细致的计数确定。在这里，我们介绍了基于散装沉积物的X射线衍射（XRD）分析的IRD的新代理。这种方法补充了从标准技术获得的结果，同时提供了几个明显的优势。除了快速生成客观数据外，对散装沉积物进行XRD测量比对单个粗岩碎屑的计数更敏感，对更宽广且更具特征的晶粒尺寸范围敏感。这项技术在对北大西洋12个沉积岩芯的研究中得到了证明。大块石英含量和石英与斜长石之比与手动计数结果呈现峰峰对应，这验证了对大量IRD涌入的识别。 XRD数据还揭示了手动识别的峰之间的差异，表明对IRD的低水平，远侧或海冰源的敏感性增加。在许多IRD事件中都出现了锯齿状图案，这支持了漂流与格陵兰岛上的大气温度变化之间的联系，并提供了气候对冰山排放影响的进一步证据。

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