The Flandrian vegetational history and environmental development of the Brede and Pannel valleys, East Sussex
This study examines the Flandrian development, particularly the vegetational history, of two valleys in the East Sussex Weald, the Brede and Pannel. Lithostratigraphic surveys of these valleys and biostratigraphic investigations from a number of key sites, principally using the technique of pollen analysi, have been undertaken. Radiocarbon dates provide a chronological framework. In the lower Brede valley pre-Flandrian colluvial deposits are overlain by estuarine sediments and a thin intermittent peat. Widespread peat formation began c.6000 BP., when alder fen woodland became established on the floodplain. Estuarine conditions returned after c.1800 B.P. The sedimentary history of the Pannel appears to be similar, although the deposits at.Paünel Bridge are unusual. Here 1 2.5m of organic material has accumulated since the beginning of the Flandrian. Comparisons are made with other coastal localities in East Sussex in order to determine the importance of local, against regional processes, in the formation of these sequences. At Pannel Bridge the pollen record extends back to 10000 B.P. when the vegetation was dominated by Pinus. Macrofossils remains of Alnus glutinosa were found indicating the presence of this species at the opening of the Flandrian. Corylus was the first of the deciduous taxa to expand (c.9400 B.P.) , followed by Quercus and tjlrnus (c.9000 B.P.). Tilia became an important component of the vegetation after c.7000 B.P. The nature of' the mid-Flandrian forests has been examined in some detail in the Brede valley. At Old Place investigations were undertaken to elucidate the pattern of pollen distribution across the floodplain. Sites close to the valley sides contain particularly high frequencies of Tilia pollen, indicating Tilia was abundant in the adjacent slope woodland. Limited interference by man on the vegetation may have occurred prior to, and accompanying the 'elm decline'. However, there is no evidence to suggest major episodes of forest clearance prior to the declines in Tilia dated to c.3700 B.P. This study highlights some of the problems in interpreting pollen assemblages from deposits of rich-fen origin.