Indian-Asian monsoon has oscillated between warm/wet interglacial periods and cool/dry glacial periods with periodicities closely linked to variations in Earth’s orbital parameters. However, processes that control wet versus dry, i.e. aridity cyclical periods on the orbital time-scale in the low latitudes of the Indian-Asian continent remain poorly understood because records over millions of years are scarce. The sedimentary record from International Ocean Discovery Program (IODP) Expedition 359 provides a well-preserved, high-resolution, continuous archive of lithogenic input from the Maldives reflecting on low-latitude aridity cycles. Variability within the lithogenic component of sedimentary deposits of the Maldives results from changes in monsoon-controlled sedimentary sources. Here, we present X-ray fluorescence (XRF) core-scanning results from IODP Site U1467 for the past two million years, allowing full investigation of orbital periodicities. We specifically use the Fe/K as a terrestrial climate proxy reflecting on wet versus dry conditions in the source areas of the Indian-Asian landmass, or from further afield. The Fe/K record shows orbitally forced cycles reflecting on changes in the relative importance of aeolian (stronger winter monsoon) during glacial periods versus fluvial supply (stronger summer monsoon) during interglacial periods. For our chronology, we tuned the Fe/K cycles to precessional insolation changes, linking Fe/K maxima/minima to insolation minima/maxima with zero phase lag. Wavelet and spectral analyses of the Fe/K record show increased dominance of the 100 kyr cycles after the Mid Pleistocene Transition (MPT) at 1.25 Ma in tandem with the global ice volume benthic δ¹⁸O data (LR04 record). In contrast to the LR04 record, the Fe/K profile resolves 100-kyr-like cycles around the 130 kyr frequency band in the interval from 1.25 to 2 million years. These 100-kyr-like cycles likely form by bundling of two or three obliquity cycles, indicating that low-latitude Indian-Asian climate variability reflects on increased tilt sensitivity to regional eccentricity insolation changes (pacing tilt cycles) prior to the MPT. The implication of appearance of the 100 kyr cycles in the LR04 and the Fe/K records since the MPT suggests strengthening of a climate link between the low and high latitudes during this period of climate transition.

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与马尔代夫大陆风化有关的200万年低纬度干旱记录

印度-亚洲季风在暖/湿冰期和冷/干冰期之间振荡，其周期性与地球轨道参数的变化紧密相关。然而，由于缺乏数百万年的记录，在印度-亚洲大陆的低纬度地区，控制湿对干的过程（即在轨道时间尺度上的干旱周期性周期）仍然知之甚少。来自国际海洋发现计划（IODP）359号探险队的沉积记录提供了保存完好的高分辨率连续记录的马尔代夫岩性输入，反映了低纬度干旱周期。马尔代夫沉积沉积物的岩性成分内部的变化是由季风控制的沉积源的变化引起的。这里，我们提供了过去两百万年来IODP网站U1467的X射线荧光（XRF）核心扫描结果，可以对轨道周期进行全面研究。我们专门将Fe / K用作陆地气候代用物，以反映印度-亚洲陆源或更远地区的干湿条件。Fe / K记录显示了轨道强迫循环，反映了冰川期的风成（冬季季风较强）相对于冰川间期的河流供应（夏季风较强）的相对重要性变化。对于我们的年代，我们将Fe / K周期调整为进动日射变化，将Fe / K最大值/最小值与零相位滞后的日射最小值/最大值联系起来。¹⁸ O数据（LR04记录）。与LR04记录相反，Fe / K曲线在1.25至200万年的时间间隔内，在130 kyr频带附近解析了100 kyr状的周期。这些类似100 kyr的周期很可能是由两个或三个倾斜周期的捆绑形成的，这表明低纬度的印度-亚洲气候变化反映了MPT之前对区域偏心日变化（步调倾斜周期）的倾斜敏感性增加。自MPT以来，LR04和Fe / K记录中出现了100 kyr周期，这暗示着在这一气候过渡时期低纬和高纬之间的气候联系得到加强。