The BGS Lexicon of Named Rock Units — Result Details

Schiehallion Boulder Bed Formation

Computer Code: DBST Preferred Map Code: SchB
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Lower part: Calcareous diamictite with dominantly calcareous clasts. Central part: Schistose and feldspathic psammite and quartzite (discontinuous). Upper part: Quartz-rich diamictite with dominantly granite and quartzite clasts.
Definition of Lower Boundary: Gradation from biotite calc-pelite to calcareous diamictite over 10m.
Definition of Upper Boundary: Sharp contact between quartzose diamictite and thinly-bedded quartzite. However, 10 - 20m bed of reworked granite diamictite occurs near base of Schiehallion Quartzite Formation on Cnoc nan Aighean.
Thickness: 0 - 250m in Sheet 55W
Geographical Limits: From east end of Loch Errochty [NN 7190 6609] to Loch Kinardochy [NN 775 550] west of Loch Tay Fault; around Loch Tummel [NN 833 596] and at Kirkton of Lude [NN 900 690], east of Loch Tay Fault.
Parent Unit: Islay Subgroup (DBIS)
Previous Name(s): Schiehallion Boulder Bed (-201)
Schichallion Boulder Bed (-1484)
Tillite (Banffshire) [Obsolete Name And Code: See DBIS, DBST, DBPT] (DBBT)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Northern slopes of Schiehallion, on western side of Meall nan Aighean. 
Reference(s):
Treagus, J E. 2001. Solid geology of the Schiehallion district. Memoir of the British Geological Survey, Sheet 55W (Scotland). 
Bailey, E B, 1925. Perthshire tectonics: Loch Tummel, Blair Atholl and Glen Shee. Transactions of the Royal Society of Edinburgh, Vol.53, 671-698. 
Bailey, E B and McCallien, W J, 1937. Perthshire tectonics: Schiehallion to Glen Lyon. Transactions of the Royal Society of Edinburgh, Vol.59, 79-117. 
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). 
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. 
Stephenson, D and Gould, D , 1995. British Regional Geology: the Grampian Highlands (4th edition). (London: HMSO for the British Geological Survey), 67-68. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S055 S055 S056