Controls on Palaeogene deep-sea diatom-bearing sediment deposition and comparison with shallow marine environments

Abstract. Diatoms are the key players in the present-day global biogeochemical cycles. Yet, the diatom flux response to the dynamically changing climates of the Palaeogene has long been a subject to divergent interpretations. We present a compilation of Palaeogene deep-sea diatom-bearing sediments in order to gain new insight into inter-basin and latitudinal distribution of diatom accumulation zones from the K/Pg boundary to the Oligocene/Miocene transition. Our dataset includes 189 sites drilled in the Atlantic, Pacific, and Indian oceans, and in the Arctic. It suggests that the number and distribution of deep-sea diatom- bearing sediment occurrences is mainly controlled by the nutrient availibility and ocean circulation. Climate appears to have only an indirect correlation with our results, which may be linked to the expansion of the Antarctic Ice Sheet during the Oligocene global cooling. A comparison of our results with the temporal ditribution of shallow marine diatomite occurrences (Figus et al., 2024a) suggests that the increase in the number of deep-sea diatom-bearing sediment occurrences (particularly in the Atlantic) during the diatomite gap (~46 to ~44 Ma) is probably related to the tectonic reorganizations occurring during this period. These palaeogeographic changes caused the cessation of shallow marine diatomite deposition, and an increase in nutrient availability through continental weathering intensification.