Plateau deposits of the southern Chiltern Hills

Abstract

Contrary to recent usage but in accordance with Whitaker's original proposal it is suggested that the term Clay-with-flints be restricted to reddish coloured, highly tenacious clay containing flints found immediately overlying Chalk. Other associated heterogeneous flinty and clayey upland deposits usually containing appreciable sand are referred to as Plateau Drift. Definitions of these deposits are given in terms of their macro- and micromorphology, mechanical composition, mineralogy, field distribution and geomorphic relationships. Clay-with-flints appears to have been formed mainly during early Pleistocene interglacials and in late Tertiary times; since the time of the Winter Hill Terrace formation has been insignificant. Clay illuviation and possibly clay synthesis from the weathering products of overlying pervious deposits, in addition to Chalk solution which provides the flints, are considered to be involved in the formation of Clay-with-flints. The formation of Plateau Drift, which is thought to be a more or less crude mixing of Clay-with-flints with Reading Beds and, at particular elevations, with marine and fluviatile gravels and sands, may have resulted from either periglacial or glacial conditions early in the Pleistocene.