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 sample s from the Weald and from outcrop material collected in Dorset, Wiltsh ire and on the Isle of Wight. Of the twenty-one taxa represented, thre e are new: Globator rectispirale, Clypeator britannicus and Sphaerocha ra andersonii; three new combinations are proposed: Globator praecurso r, Globator protoincrassatus and Atopochara triquetra. The Chinese Val anginian species Flabellochara xiangyunensis is recognized for the fir st time in Europe. In the context of the phylogeny of the Family Clava toraceae, G. rectispirale represents the Jurassic ancestor of the Glob ator lineage and a separate origin is suggested for both Flabellochara and Clypeator. The correlations established with the Tethyan realm lo cate the Jurrassic-Cretacous boundary within the Lulworth Formation of the Purbeck Limestone Group; in this context, the whole 'Purbeck' seq uence of Swindon (Wiltshire) is attributed to the Upper Tithonian. The distribution of Clavatoraceae indirectly confirms the contemporaneity of the Boreal Galbanites kerberus and Titanites anguiformis with the Tethyan 'Durangites' ammonite zones. For the Wealden Supergroup, the c harophyte data affirm the Hauterivian-Barremian boundary at the base o f the upper division of the Weald Clay and the Upper Barremian is iden tified at the base of the Vectis Formation of the Isle of Wight.