Provenance and Weathering of Clays Delivered to the Bay of Bengal During the Middle Miocene: Linkages to Tectonics and Monsoonal Climate
Provenance and Weathering of Clays Delivered to the Bay of Bengal During the Middle Miocene: Linkages to Tectonics and Monsoonal Climate
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DOI：
10.1029/2020pa003917
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发表时间：
2020-11
影响因子：
3.5
通讯作者：
L. Bretschneider;E. Hathorne;Huang Huang-Huang;J. Lübbers;K. Kochhann;A. Holbourn;W. Kuhnt;R. Thiede;D. Gebregiorgis;L. Giosan;M. Frank
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文献类型：
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作者：
L. Bretschneider;E. Hathorne;Huang Huang-Huang;J. Lübbers;K. Kochhann;A. Holbourn;W. Kuhnt;R. Thiede;D. Gebregiorgis;L. Giosan;M. Frank
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制度，这是通过碳循环反馈对全球气候演变的重要贡献。然而，控制陆源粘土输入孟加拉湾的详细机制在构造到轨道的时间尺度上还没有被很好地理解。我们为国际海洋发现计划站点U1443(孟加拉湾南部)制作了轨道尺度分辨率的地球化学记录，时间跨度为中新世中晚期(15.8-9.5 Ma)的五个关键气候区间。我们新的放射性成因粘土的锶、钕和铅同位素时间序列表明，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，来自不同侵蚀源的个体贡献总体上保持了显著的一致。然而，在轨道时间尺度上，来自五个调查间隔的高分辨率数据显示，所有三个同位素系统都有显著的波动。有趣的是，在中新世气候最佳期(约16-15 Ma)和全球主要降温时期(约13.9-13.8 Ma)至~13.5 Ma期间，这种变化比更年轻的时段要高得多。这种变化归因于高喜马拉雅侵蚀产物供应的主要限制，这是由于峰值降雨区向喜马拉雅山脉和印度-缅甸山脉的前缘区域迁移所致。放射性同位素信号在轨道时间尺度上的瞬时漂移很可能反映了气候驱动的季风强度的变化。
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.