The Brassington Formation of Derbyshire and Staffordshire in the southern Pennine hills of central England is a succession of sands, gravels and clays preserved within karstic cavities in Carboniferous Limestone. Varicoloured clays and a thin lignite within the uppermost unit (the Kenslow Member) at Kenslow Top Pit near Friden, Derbyshire has yielded abundant pollen, spores and plant remains. The palynoflora was previously assigned to the Late Miocene to Early Pliocene. The Brassington Formation is reinterpreted here as being Tortonian (Late Miocene) in age based on the presence of the key pollen taxa Symplocos, Tricolpopollenites liblarensis and Tricolpopollenites microhenrici. The Tortonian age of the Brassington Formation means that it is the most extensive well-dated onshore Miocene unit in the UK. This refined age assessment also indicates that the rate of continuous uplift of the southern Pennines during Alpine mountain building was 0.03–0.06 mm a−1; this is significantly lower than has been recently suggested. Using the coexistence approach on the Kenslow Member palynofloras, a median value for the mean annual temperature is about 16°C.