Chalk Landforms of Southern England and Quaternary Landscape Development

Abstract

The Chalklands are conspicuous in the landscape of the south-central and south-eastern England GCR region, especially the prominent escarpments of the North and South Downs and the extensive upland of Salisbury Plain. One of the most obvious features of Chalk landscape is the dense distribution of dry valleys which characterise both its dip and scarp slopes. Two groups of dry-valley sites are considered here, a morphology group (Bratton, Devil’s Dyke, and Rake Bottom), and a group noted for its sediments (Asham Quarry, Cow Gap, Devil’s Kneadingtrough, Holywell Coombe and Upper Halling). The morphology of the valleys considered in the first group, is spectacular. Each of these GCR sites is apparently associated with river capture. They display a complex morphology involving breaks of slope, sharply angular courses and, apparently, entrenched springs. Devil’s Dyke and Rake Bottom possess generally smooth slopes in contrast to the Bratton site where the slopes are incised by a wide range of channels. The formation of these valleys has attracted considerable controversy, mainly concerning the degree to which periglacial conditions, rather than ‘normal’, temperate fluvial conditions, are involved. The second group of Chalkland GCR sites is associated with relatively simple valleys or embayments in which natural or artificial exposures have revealed complex sediments that provided detailed environmental information, mainly from molluscan remains, but also from pollen and coleoptera in the case of the spectacular Holywell Coombe. Human artefacts were retrieved from Cow Gap, Devil’s Kneadingtrough and Holywell Coombe. At each site except perhaps Upper Halling where the record may extend back to the Mid-Devensian, the period represented by the sediments is late Devensian to Holocene time, according to conventional and AMS radiocarbon dating.