Stratigraphy of the London Clay Formation (Early Eocene) in the Hampshire Basin
Stratigraphy of the London Clay Formation (Early Eocene) in the Hampshire Basin Lithological logging and micropalaeontological analysis of selected exposures and boreholes in the London Clay Formation of the Hampshire Basin has enabled detailed correlation and subdivision of the Formation. The sediments are classified into nine main lithofacies, deposited in marine shelf and marginal-marine environments. The recognition and correlation of numerous minor stratigraphic discontinuities within the Formation enables its subdivision into 22 depositional sequences. Within each sequence, an initial marine-flooding transgressive episode characterised by glauconitic sediments is followed by progradation of shallow marine and marginal marine facies from the basin margin. Cross-stratified sands with basal erosional contacts at the top of some sequences record rapid sea-level falls, with channelling of the shelf. The depositional sequences within the London Clay Formation are mainly fourth order parasequences, and are interpreted as induced by eustatic sealevel fluctuations. The detailed stratigraphic record is used to produce a coastal on1ap curve for the time-interval covered by the London Clay Formation. 85 species of benthonic foraminiferids and 79 species of ostracods are recorded from the London Clay Formation. Their taxonomy is summarised. Other microfossil groups including calcareous 'microproblematica', planktonic foraminiferids, diatoms, serpulids and bryozoa have also been studied. The biostratigraphic significance of all these groups is assessed, and selected biostratigraphic events are utilised for correlation within the Hampshire Basin. Correlation with other areas in North West Europe is discussed. The biostratigraphic and magnetostratigraphic data is summarised in order to attempt placement of the London Clay Formation within the standard geochronological scale. The palaeogeographical context of the Hampshire Basin during the Early Eocene is assessed.