PURBECK-WEALDEN (EARLY CRETACEOUS) CLIMATES

A multidisciplinary colligation including new data and analysis of the evidence for the climates of southern Britain during c. 140 Ma. to c. 120 Ma BP (Berriasian-Barremian - ? earliest Aptian). The climate was at first hot, semi-arid and 'Mediterranean' (rather than 'monsoonal') in type, probably with seasonally opposed winds (E/W). An irregular l ong-term trend of increasing rainfall in the moister seasons is eviden t. This was probably associated with establishment of predominant west erlies during the Jurassic-Cretaceous transition and slightly lower av erage annual temperatures thereafter until Barremian times. Causes pro posed are frequent changes in the regional climatic system due to tect onically induced adjustments of relief under the special conditions of the semienclosed Purbeck-Wealden archipelago and increasing proximity of the widening Protoatlantic sea.