Area: 8.8 hectares.
A new site. Listed as of national importance in the Geological Conservation Review. In Dartmoor National Park. Common land.
Description and Reasons for Notification:
Scattered outcrops and abundant boulders of the country rocks of the Dartmoor Granite near to its margin are exposed on Leusdon Common. They illustrate the nature of the uppermost wall and lower roof of this intrusion of Permo-Carboniferous age.
A striking feature of the site is its demonstration of xenoliths of the country rock, showing all stages of assimilation, enclosed within the granite. These xenoliths originated by the ‘stoping’ or spalling off of solid fragments of country rock, and their incorporation into the molten granite magma.
Elsewhere on the Common somewhat different granite/country rock relationships can be seen. The granite and country rocks are intimately interleaved – a feature which reflects repeated injection of molten granite magma and the response of the solid country rocks by plastic deformation.
Leusdon Common is significant as perhaps the best site in south-west England at which to study such complex field relations at the contact between a Cornulian granite and its aureole rocks.