The BGS Lexicon of Named Rock Units — Result Details

Grampian Group

Computer Code: GRAM Preferred Map Code: Gram
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Locally arkosic quartzofeldspathic psammite in units 100-1000m thick, with subsidiary semipelite to pelite units. Quartzite units occur locally towards the top of the succession. Amphibolite and calcsilicate rock are rare. Succession from Grampian Group into Lochaber Subgroup continuous in some areas, e.g. Schiehallion, Banffshire, but in Glen Spean there may be a modified unconformity at the base of the Leven Schist.
Definition of Lower Boundary: Not seen.
Definition of Upper Boundary: Generally sharp transition from uniform psammite, generally flaggy, with thin quartzite and semipelite units of underlying Grampian Group, to better sorted psammite or quartzite and semipelite or pelite.
Thickness: Up to 5km in any one area; total thickness estimated at 9km.
Geographical Limits: Eastward from the Great Glen over much of the central Grampian Highlands as far as Cullen (Banffshire), Braemar (Aberdeenshire), Tummel Bridge (Perthshire) and almost to Dalmally (Argyll). In Ireland occurs at the southern extremity of the Dalradian outcrop in Donegal, and also on the north coast of County Mayo around Belmullet, and on Achill Island.
Parent Unit: Dalradian Supergroup (DALN)
Previous Name(s): Struan Flags (-1572)
Grampian Division [Obsolete Name And Code: Use GRAM] (MD)
Eilde Flags (-938)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  (For upper part of Group). River Leven from 2km east of Kinlochleven to west end of Blackwater reservoir. Treagus, 1974. 
Type Area  Fort Augustus to Loch Laggan. Glover and Winchester, 1989. 
Reference(s):
Harris, A L, Baldwin, C T, Bradbury, H J, Johnson, H D and Smith, R A, 1978. Ensialic basin sedimentation: the Dalradian supergroup in Bowes, D R and Leake, B E (editors): Crustal evolution in northwestern Britain and adjacent regions. Geological Journal Special Issue, Vol.10, 115-138. 
Harris, A L, Haselock, P J, Kennedy, M J and Mendum, J R, 1994. The Dalradian Supergroup in Scotland, Shetland and Ireland. 33-53 in Gibbons, W E and Harris, A L (editors). A revised correlation of Precambrian rocks in the British Isles. Special Report of the Geological Society, London, No.22. 
Bailey, E B and Maufe, H B, 1960. The geology of Ben Nevis and Glen Coe (Second Edition). Memoir of the Geological Survey of the United Kingdom. (Scotland, Sheet 53). 
Barrow, G, Grant Wilson, J S and Cunningham Craig, E H, 1905. The geology of the country around Blair Atholl, Pitlochry and Aberfeldy. Memoir of the British Geological Survey, Scotland (Sheet 55). 
Glover, B W and Winchester, J A, 1989. The Grampian Group, a major Late Proterozoic clastic sequence in the Central Highlands of Scotland. Journal of the Geological Society, London. Vol.146, 85-96. 
Johnstone, G S, 1975. The Moine Succession. 30-42 in Harris, A L, Shackleton, R M, Watson, J, Downie, C, Harland, W B and Moorbath, S (editors). A correlation of Precambrian rocks in the British Isles. Special Report of the Geological Society, No.6. 
Stephenson, D and Gould, D , 1995. British Regional Geology: the Grampian Highlands (4th edition). (London: HMSO for the British Geological Survey), 67-68. 
Treagus, J E, 1974. A structural cross-section of the Moine and Dalradian rocks of the Kinlochleven area, Scotland. Journal of the Geological Society of London, Vol.130, 525-544. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S055 S064 S086 S096 S046 S053 S045 S046 S053 S054 S054 S055 S062 S063 S063 S064 S065 S073 S073 S074 S074 S075 S083 S084 S084 S085 S085 S095 S096