The Pleistocene braided river deposits in the Blackwater Valley area of Berkshire and Hampshire, England

The drift deposits of the area southeast of Reading have been re-evaluated using the data available from over 200 shallow boreholes drilled for the Institute of Geological Sciences. Using morphometric analysis, the deposits have been reclassified as a series of terrace levels of the rivers Blackwater, Hart, Loddon and Whitewater. The most extensive spread of river terrace deposits which forms the Yateley Common plateau is correlated with the Black Park Terrace in the classical terrace sequence of the Middle Thames. Despite the large number of samples analysed, the variations in grain size and composition of the deposits do not show any significant trends across the study area. Calculation of the palaeohydrology of the deposits indicates bankfull discharges ranging from about 30 to 60 times the values recorded for the present-day river Blackwater. It is suggested that the terrace deposits represent the periglacial aggradation of a braided river system issuing from the North Downs and that they are related to successive cold phases of the Pleistocene period.