The BGS Lexicon of Named Rock Units — Result Details

Crawton Group [Obsolete Name And Code: See Dunnottar-Crawton Group]

Computer Code: CRNG Preferred Map Code: CTN
Status Code: Index Level
Age range: Silurian Period (S) — Early Devonian Epoch (DL)
Lithological Description: Poorly-sorted volcaniclastic sandstone and conglomerate, interbedded with non-volcaniclastic conglomerate. Non-volcaniclastic deposits consist of poorly-sorted conglomerate, with angular clasts, and bimodally-sorted conglomerate with rounded clasts. The conglomerates are of markedly different provenence and were deposited from streams flowing in opposing directions. The top of the Crawton Group is characterised by the intermittent occurrence of volcanic rocks including trachybasaltic lavas and welded dacitic tuff (Lintrathen 'ignimbrite'). Flows of trachybasaltic, trachyandesitic or andesitic lava may occur at lower levels.
Definition of Lower Boundary: Base not seen, presumed to lie conformably over conglomerate of Dunnottar Group in type area. Unconformable on Dalradian elsewhere. Believed to overstep basement towards south-west.
Definition of Upper Boundary: In type area, top is taken at top of highest lava of Crawton Volcanic Formation, where this is overlain by clast-supported conglomerate at base of Arbuthnott Group. Elsewhere taken at top of thick deposit of welded tuff (Lintrathen `ignimbrite') or at base of lowest of series of lavas forming the Arbuthnott Group. Believed to be progressively overstepped towards the south-west by the Arbuthnott Group.
Thickness: Variable, maximum exposed thickness of 700m, presumably thinning westwards, where the combined thickness of the Dunnottar and Crawton Groups is less than 1500m. At the westernmost part of its outcrop, the Crawton Group has a maximum thickness of 40m (Paterson and Harris, 1969).
Geographical Limits: none recorded or not applicable
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Sea cliffs and foreshore, Crawton Bay. 
Partial Type Section  Sea cliffs and foreshore, Little John's Haven to Inverbervie. 
Partial Type Section  Sea cliffs and foreshore, Doolie Ness to Knox Hill. 
Reference(s):
Haughton, P D W, 1993. Simultaneous dispersal of volcaniclastic and non-volcaniclastic sediment in fluvial basins: examples from the Lower Old Red Sandstone, east-central Scotland. In: Marzo, M and Puigdefabregas, C. (eds) Alluvial Sedimentation. Blackwell Scientific Publications, 451-471. 
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 
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 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. 
Campbell, R, 1913. The geology of south-eastern Kincardineshire. Transactions of the Royal Society of Edinburgh, Vol.48, pp.923-960. 
Haughton, P D W, 1988. A cryptic Caledonian flysch terrane in Scotland. Journal of the Geological Society, Vol.145, 685-703. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S067 S066