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| Breckland |
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| Habitat: Earth heritage (of national significance) |
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The rocks, fossils, minerals and landforms of geological interest, together with the natural geomorphological processes that continue to shape the landscape.
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Over millennia Breckland has experienced both tropical seas and arctic tundra to produce thegeological character and landforms of the area today.
Breckland's bedrock is Cretaceous Middle and Upper Chalk, deposited as a pure limestone intropical seas between 100 and 65 million years ago. This is covered by, often thin, sandyglacial drift left behind when the Anglian ice sheet covered the area around 400,000 yearsago.
Much later this Anglian drift material was re-worked under the prevailing tundra-likeconditions of the last glacial period 100,000 - 12,000 years ago. This left a cover of wind-blown sediments which, through freeze/thaw processes on the chalk which was close to thesurface, led to Breckland's characteristic striped soils of alternating acid sands and alkalinechalk. On level ground intense tundra activity sorted the sediments to create patternedground. In aerial photographs these features look like fingerprints in the grass heathvegetation and soils of ploughed fields.
Other characteristic features of the Breckland natural area are the shallow depressions termedpingos. These also date from tundra-like conditions in the last Ice Age. Pingos form asgroundwater collects, freezes and builds up beneath the surface creating a domed feature. Asthe climate warms, the ice melts and the dome collapses, leaving a crater in the centre of thepingo and sandy ramparts around the rim. Many of the pingos in Breckland are filled, orpartially filled with water due to their close relationship with the groundwater table. TheBreckland pingos are of a particular type indicating the presence of ground ice during the IceAge. These features are important for the clues they give us to the processes and conditionsprevalent when they were formed.
Another active process has been the effect of water on the chalk bedrock which has resultedin the formation of so called karstic depressions or swallow holes, which may be evident onthe surface or hidden beneath the glacial deposits. The famous fluctuating Breckland meres,such as Ringmere or Fowlmere, may be connected to this karstic drainage, although the exactprocess of formation and age of the features has not yet been established. Several theorieshave been suggested to explain their formation including surface water drainage, pingodevelopment or collapsed underground caverns.
Breckland also has an important geoarcheological interest, with flint deposits being exploitedby early man as a source of material to fashion stone implements. Nationally importantpalaeolithic sites, some associated with the geological interest of the area, place Breckland atthe forefront of British palaeolithic study.
Several Sites of Special Scientific Interest (SSSI) in the Breckland natural area clearlydemonstrate the importance of the Ice Age and its part in the evolution of the landscape. Thetford Heath and Grimes Graves both contain excellent examples of patterned groundwhilst at Beeches Pit at West Stow sections are evident through the sequence of glacialdeposits. Deposits of tufa (calcium carbonate) which provide information on the drainagepattern, flora and fauna of the environment during the last 1.6 million years are also revealedat Beeches Pit. The Stanford Training Area SSSI provides good examples of thedevelopment of karst landforms such as chalk swallow holes, e.g. the Devil's Punch Bowl.
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