| Computer Code: |
DMR |
Preferred Map Code: |
notEntered |
| Status Code: |
Full, without ratification |
| Age range: |
Stephanian Stage (CS)
— Cisuralian Epoch (PLC) |
| Lithological Description: |
Granite with varying grain size; mostly coarse and locally porphyritic. In the north and north-east of the granite, tourmaline is a common constituent, although the amount of tourmaline and biotite varies across the granite; locally one or both minerals may be very abundant. Fine-grained granite occurs in the area around Birch Tor and Vitifer Mine. In the eastern area, the granite has a coarsely crystalline porphyritic texture, composed principally of quartz, biotite and orthoclase but locally with microperthite, albite and black tourmaline. Textures vary over short distances, with the boundaries between them being predominantly gradational. Over the whole extent of the Dartmoor Granite, more than 50% is composed of granite in which feldspar megacrysts of > 15mm compose over 10% of the rock volume. |
| Definition of Lower Boundary: |
Not known. |
| Definition of Upper Boundary: |
Present day erosional surface, with local cover of Head and/or peat. |
| Thickness: |
Not known. |
| Geographical Limits: |
Devon, UK. |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
Dartmoor Granite
(DMGR)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| Reference(s): |
| De La Beche, H T, 1839. Report on the geology of Cornwall, Devon and west Somerset. Memoir of the Geological Survey. |
| Edmonds, E A, Wright, J E, Beer, K E, Hawkes, J R, Fenning, P J, Freshney, E C, Lovelock, P E R, McKeown, M C, Ramsbottom, W H C and Williams, M. 1968. Geology of the country around Okehampton. Memoir of the Geological Survey of Great Britain, Sheet 324 (England and Wales). |
| Reid, C, Barrow, G, Sherlock, R L, MacAlister, D A, Dewey, H and Bromehead C N. 1912. The Geology of Dartmoor. Memoirs of the Geologial Survey, England and Wales. Explanation of sheet 338. |
| Brammel A, and Harwood H F. 1932. The Dartmoor Granites: genetic relationships. Quarterly Journal of the Geological Society, Vol. 88, 171-237. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E339
|
