Climate, cryosphere and carbon cycle controls on Southeast Atlantic orbital-scale carbonate deposition since the Oligocene (30–0 Ma)

Abstract. The evolution of the Cenozoic cryosphere from unipolar to bipolar over past 30 million years (Myr) is broadly known. Highly resolved records carbonate (CaCO3) content provide insight into regional and global climate, cryosphere, carbon cycle dynamics. Here, we generate first Southeast Atlantic CaCO3 record spanning last Myr, derived X-ray fluorescence (XRF) ln(Ca / Fe) data collected at Ocean Drilling Program Site 1264 (Walvis Ridge, SE Ocean). We present a comprehensive continuous depth age model for entirety (? 316 m; Myr). This constitutes key reference framework future palaeoclimatic palaeoceanographic studies this location. identify three phases with distinctly different orbital controls on deposition, corresponding major developments in cycle: (1) strong ? 110 kyr eccentricity pacing prevails during Oligocene–Miocene warmth 30–13 Ma), (2) increased eccentricity-modulated precession appears after middle Miocene Climate Transition (mMCT) 14–8 (3) pervasive obliquity late 7.7–3.3 Ma) following greater importance high-latitude processes, such as glacial activity cooling. lowest (92 %–94 %) occurs between 18.5 14.5 Ma, potentially reflecting dissolution caused by widespread early preceding Antarctic deglaciation across Climatic Optimum 17–14.5 1.5 Myr. emergence deposition 14 Ma could signal reorganisation surface and/or deep-water circulation region reglaciation mMCT. sensitivity 13 associated an increase mass accumulation rates (MARs) reflects productivity recurrent influxes cooler, less corrosive deep waters. highest (%CaCO3) MARs indicate that Miocene–early Pliocene Biogenic Bloom (LMBB) 7.8 3.3 1264; contemporaneous LMBB equatorial Pacific Ocean. At 1264, onset roughly coincides appearance %CaCO3, forcing. expression may reflect nutrient input ocean resulting enhanced aeolian dust glacial/chemical weathering fluxes, due meridional temperature gradients. Regional variability timing amplitude be driven differences cooling, continental aridification changes Miocene.