We investigate the phased evolution and variation of the South Asian monsoon and resulting weathering intensity and physical erosion in the Himalaya–Karakoram Mountains since late Pliocene time (c. 3.4 Ma) using a comprehensive approach. Neodymium and strontium isotopic compositions and single-grain zircon U–Pb age spectra reveal the sources of the deposits in the east Arabian Sea, and show a combination of sources from the Himalaya and the Karakoram–Kohistan–Ladakh Mountains, with sediments from the Indian Peninsula such as the Deccan Traps or Craton. We interpret shifts in the sediment sources to have been forced by sea-level changes that correlate with South Asian monsoon rainfall variation since late Pliocene time. We collected 908 samples from the International Ocean Discovery Program Hole U1456A, which was drilled in the east Arabian Sea. Time series of hematite content and grain size of the sediments were examined downcore. We found South Asian monsoon precipitation and weathering intensity experienced three phases from late Pliocene time. Lower monsoon precipitation, with a lower variability and strong weathering intensity, occurred during 3.4–2.4 Ma; an increased and more variable South Asian monsoon rainfall, along with strengthened but fluctuating weathering intensity, occurred at 1.8–1.1 Ma; and a reduced rainfall with lower South Asian monsoon precipitation variability and moderate weathering intensity marked the period 1.1–0.1 Ma. Maximum entropy spectral analysis and wavelet transform show that there were orbital-dominated cycles of periods c. 100 and c. 41 ka in these proxy-based time series. We propose that the monsoon, sea level, global temperature and insolation together forced the weathering and erosion in SW Asia.

中文翻译：

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上新世晚期以来南亚季风的阶段性演化和变化，以及由此产生的喜马拉雅山脉-喀喇昆仑山脉的风化和地表侵蚀，使用来自阿拉伯海核心的数据

我们研究了上新世晚期以来喜马拉雅-喀喇昆仑山脉南亚季风的阶段性演化和变化以及由此产生的风化强度和物理侵蚀。C。3.4 Ma) 采用综合方法。钕和锶同位素组成和单粒锆石 U-Pb 年龄光谱揭示了东阿拉伯海沉积物的来源，并显示了喜马拉雅山脉和喀喇昆仑山脉-科希斯坦-拉达克山脉的来源以及印度沉积物的组合半岛，如德干陷阱或克拉通。我们将沉积物来源的变化解释为自上新世晚期以来与南亚季风降雨变化相关的海平面变化造成的。我们从在阿拉伯海东部钻探的国际海洋发现计划孔 U1456A 收集了 908 个样本。对沉积物赤铁矿含量和粒度的时间序列进行了检查。我们发现南亚季风降水和风化强度从上新世晚期经历了三个阶段。3.4~2.4 Ma期间出现较低的季风降水，变率较小，风化强度强；在 1.8-1.1 Ma 发生了增加和变化更大的南亚季风降雨，以及加强但波动的风化强度；降雨减少，南亚季风降水变率较低，风化强度适中，标志着 1.1-0.1 Ma 的时期。最大熵谱分析和小波变换表明存在轨道主导的周期循环 1.8~1.1 Ma，风化强度增强，但风化强度有所波动；降雨减少，南亚季风降水变率较低，风化强度适中，标志着 1.1-0.1 Ma 的时期。最大熵谱分析和小波变换表明存在轨道主导的周期循环 1.8~1.1 Ma，风化强度增强，但风化强度有所波动；降雨减少，南亚季风降水变率较低，风化强度适中，标志着 1.1-0.1 Ma 的时期。最大熵谱分析和小波变换表明存在轨道主导的周期循环C。100 和C。在这些基于代理的时间序列中为 41 ka。我们提出季风、海平面、全球温度和日照共同推动了亚洲西南部的风化和侵蚀。