The Upper Thames basin

Abstract

This chapter is devoted to the first of three geographical divisions of the present Thames drainage system, the Upper Thames basin. This comprises the catchment areas of the various streams that combine to form the Thames upstream from the Chiltern escarpment (Fig. 2.1). In many ways the Upper Thames is most easily treated as a separate system from the valley downstream of the Goring Gap. Its Quaternary terrace record is extensive, particularly in the valley of the River Evenlode, which appears to have been the main stream until late in the Middle Pleistocene. Unfortunately, there is little preservation of terrace deposits in the area of the Goring Gap and, therefore, no continuity with the succession in the Middle Thames. This has contributed to a long-standing uncertainty over correlation between the Upper Thames terraces and those in the London Basin. The problem of correlation between the Upper and Middle Thames has been addressed in this volume using projections of sediment-body longitudinal profiles between the two areas, reinforced with biostratigraphical evidence for the age of surviving interglacial deposits (see Chapter 1 and Fig. 1.3).