Although the presence of Upper Coal Measures under the Mesozoic rocks around Burford has been known for nearly 100 years, productive Westphalian was proved for the first time in this area by the IGS Apley Barn borehole, near Witney, where Upper Carboniferous strata were entered at 250–19 m. Two further boreholes, at Steeple Aston and Withycombe Farm subsequently drilled suggest that the concealed coalfield possibly has an area of 450 sq miles. The tonnage of coal could be of the order of 10 x 109. The succession commences in the zone of Anthraconauta tenuis and correlations with the Somerset-Bristol coalfield, and with the Halesowen and Keele groups of Warwickshire are suggested. Intrusive basalts, dated at 298 m.y. and basalt-breccias were found at Steeple Aston. The pre-Carboniferous rocks encountered throw some light on gravity anomalies in the Cotswolds; the Banbury-Shipston 'high' may be a buried anticline of Silurian, while the Steeple Aston 'low' is correlated with thick Old Red Sandstone.