The stratigraphy of the Gault Formation (Early Cretaceous, Albian) in East Anglia and south-east England

Abstract

The mudstones of the Gault Formation, divided into Lower and Upper Gault Members, have been proved in boreholes to underlie the Chalk throughout south east England in all but the northern part of East Anglia. The formation outcrops along the western edge of the London Platform and the foot of the Chalk escarpments in the Weald and Wessex Basins. Lower Gault is present except in London north of the River Thames, and parts of Essex, Hertfordshire and Suffolk where early Late Albian fault reactivation led to its removal by erosion. The Upper Gault has a more continuous subcrop resting on an eroded surface ranging from Silurian to older Cretaceous rocks: it is the first Mesozoic deposit to cover the whole of the London Platform. In the western Weald and the parts of the Wessex Basin including the Isle of Wight, eastern Hampshire and Oxfordshire, the Upper Gault interdigitates with and passes laterally into the Upper Greensand Formation. Three principal classifications of the Gault currently exist: (1) the English type section at Folkestone extending to the Ashford, Kent and the Kent Coalfield subcrop (Beds I-XIII); (2) the Northern Weald in West Kent, Surrey and the subcrop beneath south London (Divisions 1–11); (3) the outcrop and subcrop in East Anglia (G1-19). The object of the present paper is to correlate these three schemes and to suggest how they might be combined into a single common seven-unit Gault classification (GE1-7). The Gault succession in the Stowlangtoft Borehole is described in an appendix.