mirrored file at http://SaturnianCosmology.Org/ For complete access to all the files of this collection see http://SaturnianCosmology.org/search.php ========================================================== Devensian Glaciation The Devensian Glaciation was the most recent glacial period. It started approximately 70,000BP and ended 10,000BP. In the early Devensian ice spread down into the Cheshire Plain from the northwest. It also spread down the East Coast, impeded drainage and creating Lake Humber and Lake Fenland. It has been argued that there was no glaciation in Wales in the early Devensian. Following a number of interstadials the ice sheets reached their maximum extent between 25,000BP and 15,000BP. At that time Holt and Little Witley were on the southern limit of the ice sheet which was centered on the Irish Sea and joined with that from Scotland and thence the North Sea. Animal species that will have occurred in the two parishes at various times during the Devensian include Arctic Lemming, Wolverine, Wolf, Arctic and Red Fox, Brown and possibly Polar Bear, Spotted Hyaena (to 32,200BP), Bison, Reindeer, Red Deer, Irish Elk, Woolly Mammoth, Woolly Rhinoceros (to 22,350BP), Horse and possibly Saiga; mostly creatures of the open tundra or steppe. Cool summers, averaging 10° C in July and severe winters typified The Devensian climate. The pine and birch forest of the late Ipswichian gave way to herbaceous plants characteristic of periglacial conditions in southern Britain i.e. seasonally snow-free conditions in zone extending approximately 200km from ice front; characterised by tundra conditions & intense frost action. Several sites shed light on the conditions of the Early Devensian, about 70,000 - 50,000BP. The mixed assemblage of plants recovered from a site dating to 70,000BP, indicate a variety of habitats that suggest braided streams and permafrost. There is evidence that shallow pools on the terrace surface became saline through intense evaporation under the cold dry climate. Strata in Victoria Cave, near Settle in Yorkshire date from approximately this time and contain remains of Reindeer & Wolverine, typical tundra species. The butchering and disarticulation of a Reindeer's back leg using stone tools created cut marks on a bone from Creswell Crags dating from 60,000-42,000 years old. This suggests that Neanderthal hunters were responsible for catching and butchering this animal. The type-site for the Chelford Interstadial dated at 65,000-59,000BP is in Cheshire. Fossil ice wedges and glacial till are exposed in a sandpit at Chelford. The sands originated as a permafrost alluvial fan emanating from the Pennines. In these sands there is a stratum containing peat and macrofossils, needles, cones, and even tree stumps and trunks. The main plant species are birch, pine and spruce and the forest type indicated is thought to be similar to that growing in northern Finland today under a cool continental climate with a mean annual temperature of about 2°C. The arctic-alpine nature of the snail, beetle and pollen assemblage corroborate this conclusion and indicate a continental climate with long, dry cold winters with a February average of -11°C and an average July temperature of less about 15°C. The type locality for the undated 'Brimpton interstadial' is situated on the River Kennet, a tributary of the Thames. This period is a temperate interlude between the Chelford & Upton Warren interstadials. The Upton Warren interstadial, named after Upton Warren near Droitwich, was a period of ameliorated climate that occurred in the mid-Devensian, approximate 42,000 - 38,000BP. At that time, the summer temperature is thought to have been about 16°C, i.e. not much cooler than present. The vegetation was largely herbaceous, with a rich variety of species of different phytogeographical and habitat affinities. As the main plant indicators of an interstadial, i.e. birch or pine/spruce are absent; some authors doubt the validity of the description of an ameliorated climate at this time. The open habitat may however be ascribed to a very high grazing intensity by a large herbivorous mammalian fauna consisting of Woolly Mammoth, Woolly Rhinoceros, Reindeer and Bison. It is also possible that other strongly adverse features existed such as very cold winters (January -15°C), severe wind exposure, severe spring thaw and flooding, and. highly unstable soils that liken the environment in the mid-Devensian to that of Siberian river floodplains. At the same time Woolly Mammoth, Woolly Rhinoceros and Horse occupied Fladbury, near Pershore. A ridge-top site in Leicestershire, dated to 30,000BP, has recently produced remains of Wooly Rhino in associations with a hyaena den. Flint spear points, produced by Neanderthals were also present. The 100 animal bones and droppings suggest the Neanderthals hunted in a land where animals such as the Woolly Rhinoceros, normally associated with cold areas, coexisted with Spotted Hyaenas, only found in Africa today. Following the interstadial cold conditions returned so that at 27,650BP Woolly Mammoth, Woolly Rhinoceros, Horse, Reindeer, Bison and Musk Ox moved through the arctic tundra at Beckford, near Pershore. The polar desert was colder and more continental than period before the Upton Warren Interstadial. In addition to the species noted at Fladbury, Arctic Lemming, Brown Bear, Arctic Fox and Spotted Hyaena roamed the landscape. The presence of certain beetles indicates 13°C summer and -17°C winter temperatures, and at some sites less than 10°C summer and -20°C winter temperatures. The habitat consisted of tundra with scattered juniper and dwarf birch in the periglacial areas in southern and midland Britain. At its maximum extent ice from Scotland and Lake District flowed into the Irish Sea and south into Cheshire Plain and Shropshire. The ice was up to 1800m thick. Due to the amount of water locked up in the ice sheets, the sea level dropped exposing large areas of the North Sea floor, which became deltas for braided channels of rivers draining Europe. The Devensian Glaciation ended gradually and unevenly as the climate ameliorated over a period of several thousand years. By 14,500BP the ice-sheet was in retreat and had possibly vanished altogether in west England and Wales. 1,500 years later the ice-sheet had disappeared completely from England, Wales and Ireland, and most of Scotland was ice-free. There may however have been residual ice in Scottish highlands through this period. The brief Windermere Interstadial occurred around 13,800 to 12,000BP. By 12,500BP summers were at least as warm as today with 17°C mean July temperature and a winter mean of 0-1°C, i.e. a more continental climate than at present. In southern Britain open-ground plant communities gave way to juniper-willow scrub vegetation then birch-pine woodland. In some regions the formation of the forest was delayed by over 800 years due possibly to grazing pressure from Irish Elk and Reindeer. Red Deer, Moose, Aurochs and Horse also occurred during the Interstadial. Some notable species put it their final British appearances during the Windermere Interstadial, e.g. Woolly Mammoth disappeared around 12,300BP and Saiga 12,100BP. Some of the most recent (12920±390BP) Mammoth remains found in Britain, recovered from Condover in Cheshire, date to this period. The bones were associated with interstadial pollen & insect assemblages. Saiga remains from Gough's Cave, Cheddar, along with those of Horse, Red Deer, Aurochs and Mountain Hare, show evidence of butchery at the hand of man. The first Upper Palaeolithic (Old Stone Age) hunter-gatherer people to return to Britain during the Windermere Interstadial made distinctive stone tools known as Creswell Points. The earliest human remains from Gough's Cave date from this period. Most artefacts belonging to the ?Creswellian? tradition have been found in the Peak District, South Wales and Southwest England. The people who used these tools were highly mobile, as can be seen in Southwest England, where the source of flint was in the upper Thames Valley, but the flints themselves were lost up to a hundred kilometres away. At a date as early as this, trading contacts seem unlikely and it is more probable that people collected the flint themselves and then discarded the tools elsewhere. The presence of an inscribed drawing of an Ibex, found recently at Creswell Crags, bears out the nomadic nature of its creator, for Ibex are not known to have occurred in Britain, but occurred in continental Europe at a time when then Britain and the Continent were still linked by a land-bridge. The size of a Palaeolithic hunter-gatherer group is difficult to judge, but 25 is regarded as a minimum breeding population for human groups. The economy was based on hunting animals and gathering wild plant foods. Evidence for the consumption of plant foods is almost non-existent. Ethnographic parallels with modern hunter-gatherer communities have been taken to show that the colder the climate, the greater the reliance on meat. There are sound biological and economic reasons for this, not least in the ready availability of large amounts of fat in arctic mammals. From this, it has been deduced that the humans of the glacial periods were primarily hunters, while plant foods were more important during the interglacials. By the late Upper Palaeolithic, the dominant food animals included Reindeer, Red Deer, Irish Elk and Aurochs. The climate warmed rapidly, and was marked by a gradual colonisation of southeastern Britain by scattered birch woodland. This compares with insect evidence, which shows that average summer temperatures right at the start of this phase were at least as high as in the post-glacial period. From about 12,500BP onwards there was step-wise climate deterioration. There was a final sudden and savagely cold spell (the Younger Dryas period = Loch Lomond Ice Advance) which started 11,000BP and lasted for 500 years, during which forest-tundra vegetation grew in an arctic climate with summer a temperature of 9°C. This period was cold enough for small glaciers re-formed in the high valleys of the Welsh mountains, Ireland & northern England (e.g. the Lake District). 200 independent ice bodies developed in Scottish Highlands & islands, the largest of which were 200km² in extent and 400 m thick. Summer temperatures were typically only 8°C in the Lake District, 7°C in the Grampians and 6°C on Skye, and only 1-2°C at sea level. Tundra and low alpine scrub rapidly replaced the woodland and heathland plant communities throughout Britain. Ptarmigan, Arctic Lemming, Northern Vole and Reindeer returned, but Cave Bear, Woolly Rhinoceros and Woolly Mammoth, did not. The last Cave Bear was possibly killed about 10,000 years ago high in the mountains of Yugoslavia. Cave Bears are estimated to have weighed near to 500kg, for males, while the females were much smaller. A typical Cave Bear skull was about 50cm long, twice the size of a Brown Bear?s skull. Alternate theories exist, but the extinction of the Cave Bear seems to be directly tied to the appearance of modern man as the replacement for Neanderthals in Europe. Furthermore, the Cave Bear was not the only species to disappear at the end of the last ice age. Cave Lions, Woolly Mammoths, Woolly Rhinoceros, Steppe Bison, Irish Elk and others all vanished. This phenomenon occurred worldwide and all the animals were either large game animals or dangerous predators. Both Cro-magnon and Neanderthal man seem to have actively sought out and destroyed Cave Bears. Brown Bears were also hunted, but these creatures seem to have been less feared by prehistoric man. Cave Bear remains have been found in Suffolk, along with bones of other game animals and predators. In several European cave sites Cave Bear skulls had been neatly stacked or arranged by human hands. The later part of Younger Dryas (i.e. 10,500-10,000BP) was markedly coldest and most arid, however the glaciers had probably disappeared from Britain and Ireland by 10,000BP. *Previous Chapter* *Next Chapter* * * *Natural History Home Page * * * *Local History Home Page* * * *Site Home Page* * E-mail *