Age and driving mechanisms of the Eocene–Oligocene transition from astronomical tuning of a lacustrine record (Rennes Basin, France)

Abstract. The Eocene–Oligocene Transition (EOT) marks the onset of Antarctic glaciation and switch from greenhouse to icehouse climates. However, driving mechanisms precise timing EOT remain controversial mostly due lack well-dated stratigraphic records, especially in continental environments. Here we present a cyclo-magnetostratigraphic sedimentological study ∼ 7.6 Myr long lacustrine record spanning late Eocene earliest Oligocene, drill core Rennes Basin (France). Cyclostratigraphic analysis natural gamma radiation (NGR) log data yields duration estimates Chrons C12r through C16n.1n, providing additional constraints on timescale. Correlations between orbital eccentricity curve 405 kyr tuned NGR time series indicate that 33.71 34.10 Ma are most likely proposed ages EO boundary. Additionally, tuning calibrates pronounced cyclicity period ∼1 Myr, matching g1–g5 term, supporting its significant expression depositional environments, hypothesizing paleolake level may have behaved as low-pass filter for forcing. Two prominent changes sedimentary facies were detected across EOT, which temporally equivalent two main climatic steps, EOT-1 Oi-1. We suggest these reflect major cooling/glacial phases via hydrological cycle, shifts drier cooler climate conditions. Finally, interval precursor glacial event is remarkably dominated by obliquity. This suggests preconditioning glaciation, either obliquity directly affecting formation/(in)stability incipient Ice Sheet (AIS), or modulation North Atlantic Deep Water production.