We present a record of glacial to Holocene ²³⁰Th_xs normalized sediment mass fluxes for a site located on the eastern flank of the Carlsberg Ridge, Arabian Sea to evaluate carbonate burial, preservation and surface ocean changes spanning the last 38 ka. Sediment fluxes (0.81–3.70 g cm⁻² ka⁻¹) indicate dominant carbonate rain (0.44–1.83 g cm⁻² ka⁻¹), followed by ²³²Th‐based lithogenic flux (0.36–1.42 g cm⁻² ka⁻¹), with higher fluxes during the Holocene and the late Marine Isotope Stage (MIS) 3 and extremely low fluxes during MIS 2. Despite large variations in sediment mass fluxes, the average flux of ²³⁰Th_xs scavenged over the last 38 ka remained nearly constant. In contrast, the large variations in the initial ²³⁰Th_xs activity display the effect of variable dilution by the carbonate flux. Analysis of ²³²Th‐based lithogenic flux documents a dominant fluvial source and links its variability to changing SW monsoon precipitation in the Indus source region. Comparison of the last 38 ka carbonate flux record with the present‐day carbonate flux intercepted at the closest mooring at 3915 m depth demonstrates burial efficiency of 80 to 99% to the seabed during the Holocene and late MIS 3 and 53% for the MIS 2. Calculated carbonate preservation efficiency relative to the trapped upper ocean carbonate flux provides evidence for a productivity control of the preserved carbonate flux, which indicates high preservation during the Holocene (63±10%), and MIS 3 (77±24%) and low during MIS 2 (41±15%). Our results suggest that the eastern flank of Carlsberg Ridge experienced enhanced carbonate production during the Holocene and MIS 3 compared to MIS 2. We suggest that changing oceanographic conditions in near‐surface waters have changed the carbonate supply to the sea floor accounting for the glacial to Holocene pattern with increased supply due to the intensified SW monsoon and reduced input associated with the weakened SW monsoon.

中文翻译：

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阿拉伯海南部230Th派生的冰川至全新世沉积物通量：对碳酸盐沉积的认识

我们提供了一个冰川到全新世的²³⁰ Th _xs归一化沉积物质量通量的记录，该记录位于阿拉伯海卡尔斯伯格山脊东部侧面，用于评估过去38 ka的碳酸盐岩埋藏，保存和地表海洋变化。沉积物通量（0.81–3.70 g cm ^-2  ka ^-1）表示主要的碳酸盐雨（0.44–1.83 g cm ^-2  ka ^-1），其次是²³² Th基成岩通量（0.36-1.42 g cm ^-2  ka ^-1）），在全新世和后期海洋同位素阶段（MIS）3期间通量较高，而在MIS 2期间通量极低。在最后38 ka清除的²³⁰ Th _xs几乎保持不变。相反，初始²³⁰ Th _xs活性的较大变化显示了碳酸盐通量可变稀释的效果。²³²分析基于的岩性通量记录了一个主要的河流源，并将其变化与印度河源区西南风季风降水的变化联系在一起。将最近的38 ka碳酸盐通量记录与目前在3915 m深度的最近系泊处截获的碳酸盐通量记录进行比较，发现在全新世和晚期MIS 3期间海床的埋藏效率为80％至99％，而MIS 2则为53％ 。计算得出的相对于被捕集的上层海相碳酸盐通量的碳酸盐保存效率为控制所保存的碳酸盐通量提供了证据，这表明全新世期间的保存率很高（63±10％），MIS 3期间的保存率很高（77±24％）。在MIS 2中（41±15％）。我们的结果表明，与MIS 2相比，全新世和MIS 3期间，Carlsberg Ridge的东部侧面碳酸盐岩产量增加。