Tectonics and regional monsoon strength control weathering and erosion regimes of the watersheds feeding into the Bay of Bengal, which are important contributors to global climate evolution via carbon cycle feedbacks. The detailed mechanisms controlling the input of terrigenous clay to the Bay of Bengal on tectonic to orbital timescales are, however, not yet well understood. We produced orbital‐scale resolution geochemical records for International Ocean Discovery Program Site U1443 (southern Bay of Bengal) across five key climatic intervals of the middle to late Miocene (15.8–9.5 Ma). Our new radiogenic Sr, Nd, and Pb isotope time series of clays transported to the Ninetyeast Ridge suggest that the individual contributions from different erosional sources overall remained remarkably consistent during the Miocene despite major tectonic reorganizations in the Himalayas. On orbital timescales, however, high‐resolution data from the five investigated intervals show marked fluctuations of all three isotope systems. Interestingly, the variability was much higher within the Miocene Climatic Optimum (around 16–15 Ma) and across the major global cooling (~13.9–13.8 Ma) until ~13.5 Ma, than during younger time intervals. This change is attributed to a major restriction on the supply of High Himalayan erosion products due to migration of the peak precipitation area toward the frontal domains of the Himalayas and the Indo‐Burman Ranges. The transient excursions of the radiogenic isotope signals on orbital timescales most likely reflect climatically driven shifts in monsoon strength.

中文翻译：

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中新世中期运至孟加拉湾的黏土的来源和风化：与构造学和季风气候的联系

构造和区域季风强度控制着流入孟加拉湾的流域的风化和侵蚀状况，这是通过碳循环反馈对全球气候演变的重要贡献。然而，目前尚不清楚在构造到轨道时间尺度上控制土质粘土向孟加拉湾输入的详细机制。我们在中新世中期至中晚期（15.8-9.5 Ma）的五个关键气候间隔内，为国际海洋发现计划站点U1443（孟加拉南部）制作了轨道规模的分辨率地球化学记录。我们新的放射性Sd，Nd 运到九十里脊的粘土的铅同位素和时间序列表明，尽管喜马拉雅山脉发生了重大的构造重组，但在中新世期间，来自不同侵蚀源的单个贡献总体上仍然非常一致。但是，在轨道时标上，来自五个调查区间的高分辨率数据显示了所有三个同位素系统的明显波动。有趣的是，在中新世最佳气候期间（约16-15 Ma）和主要的全球冷却（约13.9-13.8 Ma）直至〜13.5 Ma，其变异性要比年轻时段高得多。这种变化归因于高峰降水区向喜马拉雅山脉和印度－缅甸山脉的锋域迁移，从而对高喜马拉雅侵蚀产品的供应受到了严重限制。