Devensian

The final continental glacial advance, dating to c 115,000-10,000 BP, especially referring to a group of British deposits, stratified above Ipswichian Interglacial deposits. Much of northern England, Scotland, and Wales is covered by a blanket of Devensian tills, sands, and gravels and these sediments were deposited by the ice-sheet. South of the ice-sheet margin is a series of related pro-glacial and periglacial deposits. Most of the Devensian stage can be dated using radiocarbon, and by this means it has been correlated with the Weichselian in northwest Europe and the Wisconsin in North America. All these formations represent one cold stage and directly preceded our present period of predominantly warm climate (the Flandrian or Holocene). Not all of the Devensian deposits are strictly glacial; some contain abundant fossils which indicate warmer interstadial periods. Three interstadials have been defined in Britain: the Chelford Interstadial (c 61,000 bp); the Upton Warren Interstadial complex (45-25,000 bp), and the Windermere Interstadial (13-11,000 bp). Levallosian, Mousterian, and Upper Palaeolithic artifacts are found in Devensian deposits and bones of Homo Sapiens have been found in Devensian cave sediments.

A group of British, mainly glacial, deposits, stratified above Ipswichian interglacial deposits (see Table 6, page 419). Much of northern England, Scotland and Wales is covered by a blanket of Devensian tills, sands and gravels. These sediments were deposited by an ice-sheet which spread out from centres in Wales, the Lake District, the Pennines and southern and highland Scotland. South of the ice-sheet margin is a series of related pro-glacial and periglacial deposits. Most of the Devensian stage can be dated using radiocarbon, and by this means it has been correlated with the Weich-selian in northwest Europe and the Wisconsin in North America. All these formations represent one cold stage, which lasted from cl20,000 bp until 10,000 bp and directly preceded our present period of predominantly warm climate (the Flandrian or Holocene). Not all of the Devensian deposits are strictly glacial. Some contain abundant fossils which can be used as environmental indicators. The species present in various of such deposits indicate warmer interstadial periods amongst the generally cold Devensian climate. Three interstadials have been defined in Britain, using beetles as environmental indicators for temperature: the Chel-ford interstadial (c61,000 bp); the Upton Warren interstadial complex (45-25,000 bp) and the Windermere interstadial (13-11,000 bp). Palaeobotany supports the beetle evidence for Chelford and Windermere, where the existence of deciduous trees (birch and pine) suggests warmer temperatures. There is, however, no evidence of trees for Upton Warren, which had a tundra flora similar to the colder parts of the Deven-sian. Britain was by no means ice-covered throughout the Devensian cold stage. Icesheets seem to have appeared only during the cold stadial between 26,000 and 13,000 bp. These sheets were lost completely during the Windermere interstadial; then during the cold Loch Lomond stadial that followed only one ice cap and small glaciers were formed in the highest hills. Sea level fell during the colder parts of the Devensian, exposing the bottom of the Irish Sea, North Sea and the Channel and connecting Britain to the Continent. Levalloisian, Mousterian and Upper Palaeolithic artefacts are found in Devensian deposits. In addition, bones of Homo sapiens have been found in Devensian cave sediments.