The BGS Lexicon of Named Rock Units — Result Details

Dunalastair Quartzite Formation

Computer Code: DUNQ Preferred Map Code: DunQ
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Quartzite and quartzitic psammitic, beds 100 - 300m thick well developed; less feldspathic than Grampian Group psammites. Cross-bedding shown by feldspar-rich and heavy mineral-rich laminae.
Definition of Lower Boundary: Sharp contact with underlying Grampian Group psammites.
Definition of Upper Boundary: Sharp boundary with Dunalastair Semipelite Formation, marked by change from quartzite to mixed psammite and semipelite.
Thickness: 0 - 90m; probably much tectonic thinning.
Geographical Limits: Main development in Strath Fionan [NN 7257 7556]. Also occurs sporadically in attenuated form from closure of Errochty Synform [NN 712 671] and as far east as tributary of Allt Kynachan [NN 7609 5670]. Also occurs at the culmination caused by the intersection of the Clunes and Bohespic antiforms [NN 745 633]. Not present east of the Loch Tay Fault, where it may have been tectonically excised; however some of the rocks of the 'Banvie Burn Series' may be equivalent.
Parent Unit: Lochaber Subgroup (DALO)
Previous Name(s): Lower Beoil Banded Quartzite (-3377)
Quartzite Within Struan Flags (-877)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  600m north-east of Lochan an Daim on transect A-A' (Fig.4 of Treagus, J E. 2001). 
Reference(s):
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. 
Treagus, J E and King, G, 1978. A complete Lower Dalradian succession in the Schiehallion district, central Perthshire. Scottish Journal of Geology, Vol.14, 157-166. 
Treagus, J E. 2001. Solid geology of the Schiehallion district. Memoir of the British Geological Survey, Sheet 55W (Scotland). 
Thomas, P R, 1980. The stratigraphy and structure of the Moine rocks north of the Schiehallion Complex, Scotland. Journal of the Geological Society, London, Vol.137, 469-482. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S055