Geophysical correlation of the Aptian and Albian formations in the Wessex Basin of southern England

Using geophysical borehole log signatures and basic lithological information from sidewall cores and well-cuttings, division and correlation of the mid-Cretaceous sediments of the Wessex Basin can be achieved. A sub-Gault (early Albian) unconformity surface is mapped with some accuracy across the Hampshire–Dorset area, and the deposits of a previous, Aptian transgression are observed. The distinctive log signatures aid in facies reconstructions and sequence stratigraphical analysis: especially the onlap of basal Gault horizons onto and across basement ‘highs’. The highly variable thickness and lithological distributions characteristic of the Wealden pass upward into laterally extensive facies distributions in the Lower Greensand and Gault. Sequence boundaries are identified at the base of the Wealden; Lower Greensand; Gault; within the Gault (cristatum subzone); and base Chalk.