Abstract. The evolution of the Cenozoic Icehouse over the past 30 million years (Myr) from a unipolar to a bipolar world is broadly known; however, the exact development of orbital-scale climate variability is less well understood. Highly resolved records of carbonate (CaCO₃) content provide insight into the evolution of regional and global climate, cryosphere and carbon cycle dynamics. Here, we generate the first Southeast Atlantic CaCO₃ content record spanning the last 30 Myr, derived from X-ray fluorescence (XRF) ln(Ca/Fe) data collected at Ocean Drilling Program Site 1264 (Angola Basin side of the Walvis Ridge, SE Atlantic Ocean). We present a comprehensive and continuous depth and age model for the entirety of Site 1264 (~316 m; 30 Myr), which constitutes a key reference framework for future palaeoclimatic and palaeoceanographic studies at this site. We identify three phases with distinctly different orbital controls on Southeast Atlantic CaCO₃ deposition, corresponding to major developments in climate, the cryosphere and/or the carbon cycle: 1) strong ~110 kyr eccentricity pacing prevails during Oligo-Miocene global warmth (~30–13 Ma); 2) increased eccentricity-modulated precession pacing appears after the mid Miocene Climate Transition (mMCT) (~14–8 Ma); 3) strong obliquity pacing appears in the late Miocene (~7.7–3.3 Ma) following the increasing influence of high-latitude processes. The lowest CaCO3 content (92–94 %) occur between 18.5–14.5 Ma, potentially reflecting dissolution caused by widespread early Miocene warmth and preceding Antarctic deglaciation across the Miocene Climate Optimum (~17–14.5 Ma) by 1.5 Myr. The emergence of precession-pacing of CaCO₃ deposition at Site 1264 after ~14 Ma could signal a reorganisation of surface and/or deep-water circulation in this region following Antarctic reglaciation at the mMCT. The increased sensitivity to precession at Site 1264 is associated with an increase in mass accumulation rates (MARs) and reflects increased regional CaCO₃ productivity and/or an influx of cooler, less corrosive deep-waters. The highest %CaCO₃ and MARs indicate the late Miocene Biogenic Bloom (LMBB) occurs between ~7.8–3.3 Ma at Site 1264, which is broadly, but not exactly, contemporaneous with the LMBB in the equatorial Pacific Ocean. The global expression of the LMBB may reflect an increased nutrient input into the global ocean resulting from enhanced aeolian dust and/or glacial/chemical weathering fluxes. Regional variability in the timing and amplitude of the LMBB may be driven by regional differences in cooling, continental aridification and/or changes in ocean circulation in the late Miocene.

中文翻译：

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渐新世以来（30-0 Ma）气候，冰冻圈和碳循环对东南大西洋轨道规模碳酸盐沉积的控制

摘要。在过去的三千万年中，新生代冰室从单极向双极演化的过程已广为人知。然而，人们对轨道尺度气候变率的确切发展知之甚少。碳酸盐（CaCO ₃）含量的高度解析记录提供了对区域和全球气候，冰冻圈和碳循环动力学演变的洞察力。在这里，我们生成了第一个东南大西洋CaCO ₃内容记录跨越最后30 Myr，该记录来自在海洋钻井计划站点1264（东南大西洋沃尔维斯山脊的安哥拉盆地一侧）收集的X射线荧光（XRF）ln（Ca / Fe）数据。我们为1264号站点（〜316 m； 30 Myr）的整个区域提供了一个全面而连续的深度和年龄模型，该模型构成了该站点未来古气候和古海洋学研究的关键参考框架。我们确定了在东南大西洋CaCO ₃上轨道控制明显不同的三个阶段沉积，对应于气候，冰冻圈和/或碳循环的主要发展：1）Oligo-中新世全球暖化（〜30-13 Ma）期间，偏心起搏主要发生在约110 kyr；2）中新世中期（mMCT）（〜14-8 Ma）之后，偏心率调节的旋进步调出现。3）随着高纬度过程的增加，中新世晚期（〜7.7–3.3 Ma）出现了强烈的倾角起伏。最低的CaCO3含量（92–94％）发生在18.5–14.5 Ma之间，这可能反映了由于中新世早期广泛的暖化和中新世气候最适期（〜17–14.5 Ma）南极冰消之前1.5 Myr引起的溶解。进动步调CaCO _3的出现大约14 Ma后在1264号站点的沉积可能表明在mMCT的南极再沉积之后该区域的表面和/或深水循环发生了重组。站点1264对进动的敏感性增加与质量累积速率（MAR）的增加相关，并反映出区域CaCO ₃生产率的提高和/或涌入了凉爽，腐蚀性较小的深水。最高％CaCO ₃和MARs表示晚中新世生物成因水华（LMBB）发生在站点1264的〜7.8-3.3 Ma之间，与赤道太平洋的LMBB广泛但不完全相同。LMBB的全球表达可能反映出由于风尘和/或冰川/化学风化通量增加而向全球海洋输入的养分增加。LMBB的时间和振幅的区域差异可能是由中新世晚期冷却，大陆干旱化和/或海洋环流变化引起的区域差异驱动的。