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Abstract. The evolution of the Cenozoic cryosphere from unipolar to bipolar over the past 30 million years (Myr) is broadly known. 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 (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). This constitutes a key reference framework for future palaeoclimatic and palaeoceanographic studies at this location. We identify three phases with distinctly different orbital controls on Southeast Atlantic CaCO3 deposition, corresponding to major developments in climate, the cryosphere and the carbon cycle: (1) strong ~110 kyr eccentricity pacing prevails during Oligocene–Miocene global warmth (~30–13 Ma), (2) increased eccentricity-modulated precession pacing appears after the middle Miocene ClimateTransition (mMCT) (~14–8 Ma), and (3) pervasive obliquity pacing appears in the late Miocene (~7.7–3.3 Ma) following greater importance of high-latitude processes, such as increased glacial activity and high-latitude cooling. The lowest CaCO3 content (92 %–94 %) occurs between 18.5 and 14.5 Ma, potentially reflecting dissolution caused by widespread early Miocene warmth and preceding Antarctic deglaciation across the Miocene Climatic 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 between 14 and 13 Ma is associated with an increase in mass accumulation rates (MARs) and reflects increased regional CaCO3 productivity and/or recurrent influxes of cooler, less corrosive deep waters. The highest carbonate content (%CaCO3) and MARs indicate that the late Miocene–early PlioceneBiogenic Bloom (LMBB) occurs between ~7.8 and 3.3Ma at Site 1264; broadly contemporaneous with the LMBB in the equatorial Pacific Ocean. At Site 1264, the onset of the LMBB roughly coincides with appearance of strong obliquity pacing of %CaCO3, reflecting increased high-latitude forcing. The global expression of the LMBB may reflect increased nutrient input into the global ocean resulting from enhanced aeolian dust and/or glacial/chemical weathering fluxes, due to enhanced glacial activity and increased meridional temperature gradients. 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. 

Abstract Faulting and earthquakes occur extensively along the flanks of the East African Rift System, including an offshore branch in the western Indian Ocean, resulting in remobilization of sediment in the form of landslides. To date, constraints on the occurrence of submarine landslides at margin scale are lacking, leaving unanswered a link between rifting and slope instability. Here, we show the first overview of landslide deposits in the post-Eocene stratigraphy of the Tanzania margin and we present the discovery of one of the biggest landslides on Earth: the Mafia mega-slide. The emplacement of multiple landslides, including the Mafia mega-slide, during the early-mid Miocene is coeval with cratonic rifting in Tanzania, indicating that plateau uplift and rifting in East Africa triggered large and potentially tsunamigenic landslides likely through earthquake activity and enhanced sediment supply. This study is a first step to evaluate the risk associated with submarine landslides in the region. 

The cause of the end-Cretaceous mass extinction is vigorously debated, owing to the occurrence of a very large bolide impact and flood basalt volcanism near the boundary. Disentangling their relative importance is complicated by uncertainty regarding kill mechanisms and the relative timing of volcanogenic outgassing, impact, and extinction. We used carbon cycle modeling and paleotemperature records to constrain the timing of volcanogenic outgassing. We found support for major outgassing beginning and ending distinctly before the impact, with only the impact coinciding with mass extinction and biologically amplified carbon cycle change. Our models show that these extinction-related carbon cycle changes would have allowed the ocean to absorb massive amounts of carbon dioxide, thus limiting the global warming otherwise expected from postextinction volcanism.

 

Much of our understanding of Earth’s past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states—Hothouse, Warmhouse, Coolhouse, Icehouse—are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.