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首页> 外文期刊>Journal of quaternary science: JQS >Late Pleistocene to Holocene palaeoenvironmental variability in the north-west Spanish mountains: insights from a source-to-sink environmental magnetic study of Lake Sanabria
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Late Pleistocene to Holocene palaeoenvironmental variability in the north-west Spanish mountains: insights from a source-to-sink environmental magnetic study of Lake Sanabria

机译：西班牙西北山区晚更新世至全新世古环境变化：萨那布里亚湖从源到汇的环境磁研究的见解

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摘要

We present a source-to-sink environmental magnetic study of a sediment core from Lake Sanabria (north-west Iberian Peninsula) and rocks of its catchment. The results indicate the occurrence of magnetite, and probably also pyrrhotite, in sediments accumulated between ca. 26 and 13 cal ka BP in a proglacial lake environment. These minerals also appear to dominate the magnetic assemblage of Palaeozoic rocks from the lake catchment. This indicates that sedimentation was then driven by the erosion of glacial flour, which suffered minimal chemical transformation due to a rapid and short routing to the lake. A sharp change in magnetic properties observed in the lake sediments between 13 and 12.6 cal ka BP reflects the rapid retreat of glaciers from the lake catchment. Sediments from the upper half of the studied sequence, accumulated after 12.6 cal ka BP in a lacustrine environment with strong fluvial influence, contain magnetite and smaller amounts of maghemite and greigite. We suggest that greigite grew authigenically under anoxic conditions caused by enhanced accumulation of organic matter into the lake. The occurrence of maghemite in these sediments suggests pedogenic activity in the then deglaciated lake catchment before the erosion and transportation of detrital material into the lake.
机译：我们提出了从源头到源头的环境磁研究，该研究来自Sanabria湖（西北伊比利亚半岛）的沉积物核及其流域的岩石。结果表明，大约在两地之间堆积的沉积物中出现了磁铁矿，可能还有黄铁矿。冰川湖环境中的26和13 cal ka BP。这些矿物似乎也主导了来自湖流域的古生代岩石的磁性组合。这表明，沉积是由冰川粉的侵蚀驱动的，由于流向湖面的路线短促，其化学转化最小。在13到12.6 cal ka BP之间的湖泊沉积物中观察到的磁特性的急剧变化反映了冰川从湖泊流域迅速退缩。来自研究序列上半部分的沉积物，在12.6 cal ka BP后，在河流影响强烈的湖相环境中积累，包含磁铁矿以及少量的磁赤铁矿和钙铁矿。我们建议，在缺氧条件下，由于有机质向湖中积累的增加，钙铁矿会自然生长。这些沉积物中磁赤铁矿的存在表明，在随后的冰川消融的流域，在碎屑物质被侵蚀和运输到湖泊之前，有成岩作用。

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