Area: 2.4 hectares.
This is a new site, listed as of national importance in the Geological Conservation Review. This site is within an Area of Outstanding Natural Beauty.
Description and Reasons for Notification:
This site shows a granite porphyry (‘elvan’) dyke, some 18 m wide, unusual for its readily discernible multiple character. Three distinct, fine-grained, acidic rock-types are interpreted as representing two successive injections involving a combination of liquid, crystal and gaseous phases, as distinct from simple fluid magmatic emplacement. Internal features such as chilled margins, flow banding and xenolithic and xenocrystic fragments are well displayed. The dyke is the best example of the ‘elvan’ suite of south-west England. The suite is approximately 20 million years younger than the granites and represents the culmination of acid magmatism in south-west England during the Permian period.