Superficial deposits are widespread. Floodplain alluvium accompanies the course of the Severn itself as well as tributaries such as the Leadon, Chelt, Frome and Cam. Ancient terraces of former, more elevated floodplains mark the position of the major rivers through various glacial and inter-glacial periods in the last Ice Age. A sheet of mainly Jurassic limestone fan gravel probably covered most of the vale in the past but has since been eroded away leaving isolated deposits, most notably the Cheltenham Sand, which forms a well-draining light soil in the Cheltenham-Gloucester region.