Abstract The ability to trace and quantify sediment provenance in northwestern Patagonia is increasingly needed to properly understand modern sediment erosion and transport processes in this rapidly changing environment, and to accurately interpret sediment records from adjacent basins in terms of climate and environmental change. Nonetheless, no study so far has systematically evaluated the effectiveness of different tracers to reconstruct sediment provenance in this region. To fill this gap, we assess the effectiveness of commonly-used provenance indicators, including bulk mineralogy, major and rare earth element (REE) geochemistry, and Sr and Nd isotopes, to reconstruct sediment provenance in northwestern Patagonia. First, the ability of these tracers to discriminate between the main sources of sediment in the region is investigated, mostly using data compiled from the literature. Then, the potential of these tracers for provenance reconstruction is assessed by comparing the composition of sediments from six major Chilean rivers between 44 and 48°S to lithological proportions in their respective watersheds. The results suggest that mineralogy, major element geochemistry, and REE geochemistry can be used as qualitative tracers of sediment provenance. However, the compositional overlap between the sources and the relatively large variability within them prevent quantitative reconstructions. By comparison, 87Sr/86Sr and eNd allow to clearly differentiate between the sources, most likely due to significant age differences between the main lithologies, and to estimate the relative contribution of each source. End-member mixing results based on Sr and Nd isotopes show that the relative source contributions are in general agreement with the lithological proportions in the river watersheds. Differences between estimated contributions and lithological proportions in the watersheds are interpreted as the result of the high regional precipitation gradient and unequal glacier distribution, which lead to variable erosion rates across the study area. Our results demonstrate the suitability of 87Sr/86Sr and eNd for quantitative provenance reconstruction in northwestern Patagonia. They constitute a strong basis for the interpretation of sediment archives from the Patagonian fjords and from the eastern South Pacific, and they should be particularly useful to quantitatively investigate modern and past earth-surface processes.

中文翻译：

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巴塔哥尼亚河西北部沉积物的来源 (44–48°S)：矿物学、地球化学和同位素示踪剂的批判性评价

摘要 越来越需要追踪和量化巴塔哥尼亚西北部沉积物来源的能力，以正确理解这种快速变化环境中的现代沉积物侵蚀和输送过程，并根据气候和环境变化准确解释邻近盆地的沉积物记录。尽管如此，到目前为止，还没有研究系统地评估了不同示踪剂在该地区重建沉积物来源的有效性。为了填补这一空白，我们评估了常用物源指标的有效性，包括大块矿物学、主要和稀土元素 (REE) 地球化学以及 Sr 和 Nd 同位素，以重建巴塔哥尼亚西北部的沉积物来源。首先，研究了这些示踪剂区分该地区主要沉积物来源的能力，主要使用从文献中收集的数据。然后，通过比较 44 至 48°S 之间智利六条主要河流的沉积物组成与其各自流域的岩性比例，评估这些示踪剂用于物源重建的潜力。结果表明，矿物学、主要元素地球化学和稀土元素地球化学可作为沉积物来源的定性示踪剂。然而，来源之间的成分重叠和它们内部相对较大的可变性阻止了定量重建。相比之下，87Sr/86Sr 和 eNd 可以清楚地区分来源，很可能是由于主要岩性之间的显着年龄差异，并估计每个来源的相对贡献。基于 Sr 和 Nd 同位素的端元混合结果表明，相对源贡献与河流流域的岩性比例基本一致。流域中估计贡献和岩性比例之间的差异被解释为区域降水梯度高和冰川分布不均的结果，这导致整个研究区的侵蚀率各不相同。我们的结果证明了 87Sr/86Sr 和 eNd 适用于巴塔哥尼亚西北部的定量来源重建。它们构成了解释巴塔哥尼亚峡湾和南太平洋东部沉积物档案的有力基础，它们对于定量研究现代和过去的地球表面过程尤其有用。