The BGS Lexicon of Named Rock Units — Result Details

Dunnottar-Crawton Group

Computer Code: DRCR Preferred Map Code: DRCR
Status Code: Full
Age range: Ludlow Epoch (SU) — Lochkovian Age (DO)
Lithological Description: Conglomerate, clast-supported, with angular to well-rounded boulders, cobbles and pebbles. In the lower part these consist predominantly of lava, psammite and quartzite, but in the upper part the conglomerates are of markedly different provenance and were deposited from streams flowing in opposing directions. Poorly-sorted volcaniclastic sandstone and conglomerate are interbedded with non-volcaniclastic conglomerate. Non-volcaniclastic deposits consist of poorly-sorted conglomerate, with angular clasts, and bimodally-sorted conglomerate with rounded clasts. Flows of trachybasalt, trachyandesite and andesitic lava occur in the lower and middle parts of the group. The top of the Dunnottar-Crawton Group is characterised by the intermittent occurrence of volcanic rocks including trachybasaltic lavas and welded dacitic tuff (Lintrathen Tuff Member).
Definition of Lower Boundary: Base of Downie Point Conglomerate Member (Dunnottar Castle Conglomerate Formation), where thickly-bedded or massive conglomerate overlies pebbly sandstone of Carron Sandstone Formation with apparent conformity. This marks the base of a thick, conglomerate-dominated succession.
Definition of Upper Boundary: In the type area, this is taken as the top of the highest lava of the Crawton Volcanic Formation, where it is overlain by a clast-supported conglomerate at the base of the Arbuthnott-Garvock Group. Elsewhere it is taken as the top of the thick deposit of welded tuff (Lintrathen Tuff Member), or at the base of the lowest of the series of lavas belonging to the Arbuthnott-Garvock Group. Believed to be progressively overstepped towards the south-west by the Arbuthnott-Garvock Group.
Thickness: Variable; 3300m in the Stonehaven area, thinning southwestward to less than 1500m. Presumed to be overlapped by younger groups to the southwest.
Geographical Limits: Northeastern Midland Valley of Scotland, Lintrathen to Stonehaven.
Parent Unit: Not Applicable (-)
Previous Name(s): Crawton Group [Obsolete Name And Code: See Dunnottar-Crawton Group] (CRNG)
Dunnottar Group [Obsolete Name And Code: See Dunnottar-Crawton Group] (DRG)
Glasslin Burn Conglomerate Formation [Obsolete Name And Code: See DRCR] (GBC)
Dunnottar And Crawton Groups [Undifferentiated] (-870)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Sea cliffs and foreshore, Crawton Bay. 
Type Section  Sea cliffs from Downie Point to Mons Crag. Can compare stratotypes of component Dunnottar Castle Conglomerate,Tremuda Bay Volcanic, Gourdon Sandstone, Whitehouse Conglomerate and Crawton Volcanic Formations. 
Partial Type Section  Sea cliffs and foreshore, Doolie Ness to Knox Hill. Little John's Haven to Inverbervie. 
Reference(s):
Browne, M A E, Smith, R A and Aitken, A M. 2001. A lithostratigraphical framework for the Devonian (Old Red Sandstone) rocks of Scotland south of a line from Fort William to Aberdeen. Version 3. British Geological Survey Research Report RR/01/04. 
Westoll, T S. 1951. The vertebrate-bearing strata of Scotland. 18th International Geological Congress, London, 1948, Vol. 9, p. 5-21. 
Armstrong, M and Paterson, I B, 1970. The Lower Old Red Sandstone of the Strathmore Region. Report of the Institute of Geological Sciences No.70/12 
Campbell, R, 1913. The geology of south-eastern Kincardineshire. Transactions of the Royal Society of Edinburgh, Vol.48, pp.923-960. 
Armstrong, M, Paterson, I B and Browne, M A E, 1985. Geology of the Perth and Dundee district. Memoir of the British Geological Survey, Sheets 48W, 48E and 49 (Scotland). 108pp. 
Haughton, P D W, 1989. Structure of some Lower Old Red Sandstone conglomerates, Kincardineshire, Scotland: deposition from late-orogenic antecedent streams? Journal of the Geological Society, Vol.146, 509-525. 
Carroll, S, 1994. Geology of the Inverbervie and Catterline district, 1:10 000 sheets NO87NW, NO87NE and NO87SW. British Geological Survey, Technical Report, WA/94/20. 
Haughton, P D W, 1988. A cryptic Caledonian flysch terrane in Scotland. Journal of the Geological Society, Vol.145, 685-703. 
Haughton, P D W and Halliday, A N, 1991. Significance of a late Caledonian igneous complex revealed by clasts in Lower Old Red Sandstone conglomerates, central Scotland. Geological Society of America Bulletin, Vol.103, 1476-1492. 
Carroll, S, 1994. Geology of the Stonehaven District. 1:10 000 Sheets NO88NW, NO88NE, NO88SW and NO88SE. British Geological Survey Technical Report WA/94/19. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S056 S067 S066 S056 S066