European Palaeobotany and Palynology Conference 2026

Palaeoclimate reconstruction of the Oligocene provides context for an Earth system with an established Antarctic ice sheet and elevated pCO2 (600—800 ppm). The palynology of 24 samples from borehole 73/36, which was drilled in the Stanley Bank Basin, Bristol Channel, offshore southwest England, were processed using acid-free techniques and 15 were found to be productive. Pollen assemblages, counted and identified using a combination of light and scanning electron microscopy, were then used to reconstruct the vegetation and palaeoclimate. The reconstructed flora was primarily composed of mixed forest and riparian wetland types. The reconstructed palaeoclimate falls into three Koppen-Geiger climate classifications: a temperate, warm-summer palaeoclimate-type with dry-winters (Cwa) for most depths, except those at 18.98 m and 10.15 m which reconstructed the same temperature regime, but with no overall dry season (Cfa) and a warm, wet-summer type (Cwb) was reconstructed at 11 m depth. A reduction of 1—3 °C in MAT and MTWQ was, likely, a Svalbardella-cooling event. With reconstructed winter temperatures lower than present-day values, it is unlikely that the proto-Atlantic Meridional Overturning Circulation was established during the Oligocene.