Article: Charophyte biostratigraphy of the Purbeck and Wealden of southern England

The distribution of charophyte assemblages in the Purbeck and Wealden sequence of southern England has been established from borehole samples from the Weald and from outcrop material collected in Dorset, Wiltshire and on the Isle of Wight. Of the twenty-one taxa represented, three are new: Globator rectispirale, Clypeator britannicus and Sphaerochara andersonii; three new combinations are proposed: Globator praecursor, Globator protoincrassatus and Atopochara triquetra. The Chinese Valanginian species Flabellochara xiangyunensis is recognized for the first time in Europe. In the context of the phylogeny of the Family Clavatoraceae, G. rectispirale represents the Jurassic ancestor of the Globator lineage and a separate origin is suggested for both Flabellochara and Clypeator. The correlations established with the Tethyan realm locate the Jurassic-Cretaceous boundary within the Lulworth Formation of the Purbeck Limestone Group; in this context, the whole 'Purbeck' sequence of Swindon (Wiltshire) is attributed to the Upper Tithonian. The distribution of Clavatoraceae indirectly confirms the contemporaneity of the Boreal Galbanites kerbems and Titanites anguiformis with the Tethyan 'Durangites' ammonite zones. For the Wealden Supergroup, the charophyte data affirm the Hauterivian-Barremian boundary at the base of the upper division of the Weald Clay and the Upper Barremian is identified at the base of the Vectis Formation of the Isle of Wight.