Some problems concerning the Early Tertiary climate of southern Britain

Abstract

Some of the problems of interpreting the Early Tertiary climate of southern England are reviewed. The London Clay flora is not thought to represent a true Tropical Rain Forest climate, but a climatic type not represented at the present day. The climate was seasonal, but frostless; rainfall was higher for the latitude than that of today; temperatures were elevated, though not necessarily as high as those in Tropical Rain Forest areas today. Tropical plants lived near low-lying rivers and lakes, where edaphic moisture supplemented rainfall and where higher atmospheric humidity occurred. If the extra-tropical plants from the London Clay were truly contemporaneous with the tropical forms, it is suggested that they grew further away from these bodies of water under less humid conditions, though not in higher altitudes. During the Oligocene, the climate in southern Britain was comparable to Eastern Margin Warm Temperate conditions of the present day. Its occurrence on the western margin of a continent reflects rainfall distributed throughout the year, and introduced by a second belt of Westerlies or moisture bearing winds from the Tethys. Arid conditions in the Paris Basin, deduced from Oligocene gypsum deposits, could not have existed contemporaneously with such conditions in southern England. Alternating pluvial and dry climatic periods are therefore inferred.