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首页> 外文期刊>Geochemistry, geophysics, geosystems >South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea
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South Asian monsoon history over the past 60 kyr recorded by radiogenic isotopes and clay mineral assemblages in the Andaman Sea

机译：安达曼海的放射性同位素和粘土矿物组合记录了过去60年的南亚季风历史

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The Late Quaternary variability of the South Asian (or Indian) monsoon has been linked with glacial-interglacial and millennial scale climatic changes but past rainfall intensity in the river catchments draining into the Andaman Sea remains poorly constrained. Here we use radiogenic Sr, Nd, and Pb isotope compositions of the detrital clay-size fraction and clay mineral assemblages obtained from sediment core NGHP Site 17 in the Andaman Sea to reconstruct the variability of the South Asian monsoon during the past 60 kyr. Over this time interval epsilon Nd values changed little, generally oscillating between -7.3 and -5.3 and the Pb isotope signatures are essentially invariable, which is in contrast to a record located further northeast in the Andaman Sea. This indicates that the source of the detrital clays did not change significantly during the last glacial and deglaciation suggesting the monsoon was spatially stable. The most likely source region is the Irrawaddy river catchment including the Indo-Burman Ranges with a possible minor contribution from the Andaman Islands. High smectite/(illite+chlorite) ratios (up to 14), as well as low Sr-87/Sr-86 ratios (0.711) for the Holocene period indicate enhanced chemical weathering and a stronger South Asian monsoon compared to marine oxygen isotope stages 2 and 3. Short, smectite-poor intervals exhibit markedly radiogenic Sr isotope compositions and document weakening of the South Asian monsoon, which may have been linked to short-term northern Atlantic climate variability on millennial time scales.
机译：南亚（或印度）季风的第四纪晚期变率与冰川间冰期和千年尺度的气候变化有关，但过去流向安达曼海的流域的降雨强度仍然受到限制。在这里，我们使用从安达曼海沉积核心NGHP站点17获得的碎屑黏土级分和黏土矿物组合的放射性Sr，Nd和Pb同位素组成，来重建过去60年来南亚季风的变化性。在此时间间隔内，εNd值变化不大，通常在-7.3和-5.3之间振荡，并且Pb同位素特征基本不变，这与安达曼海东北方的记录形成了鲜明对比。这表明碎屑粘土的来源在最后的冰川和冰消期没有明显改变，表明季风在空间上是稳定的。最有可能的来源地区是伊洛瓦底江流域，包括印度-缅甸山脉，而安达曼群岛的贡献可能很小。全新世时期绿土/（伊利石+绿泥石）比率高（高达14）以及低Sr-87 / Sr-86比率（0.711）表明与海洋氧同位素阶段相比，化学风化作用增强，南亚季风更强参见图2和3。蒙脱石贫瘠的短间隔显示出显着的放射性Sr同位素组成，并记录了南亚季风的减弱，这可能与千禧年尺度上北大西洋的短期气候变化有关。

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