The BGS Lexicon of Named Rock Units — Result Details

Cromlix Mudstone Formation

Computer Code: CXF Preferred Map Code: CLX
Status Code: Full
Age range: Emsian Age (DE) — Emsian Age (DE)
Lithological Description: Characteristically soft, bright red to dull brownish-red, maroon or purplish-brown, with green reduction spots in the north-eastern Midland Valley, generally massive but often thinly laminated, poorly-sorted, fine-grained silty sandstones, sandy siltstones, siltstones and mudstones, which lithologies may be locally interbedded with thin lenses of medium to coarse-grained pebbly sandstone.
Definition of Lower Boundary: Conformable, locally diachronous or interfingered base of red, massive or laminated and poorly-sorted, siltstone or mudstone, overlying fine- to medium-grained cross-bedded sandstone or conglomerate of the Arbuthnott-Garvock Group.
Definition of Upper Boundary: Conformable and gradational, generally diachronous, interfingering with and passing up into the Teith Sandstone Formation (or former Edzell Sandstone Formation) with increasing abundance of sandstone lithologies.
Thickness: From 240 m to 1200 m, passing laterally into the Teith Sandstone Formation (or former Edzell Sandstone Formation) towards the northwest.
Geographical Limits: Northern Midland Valley, between Stirling and Drumlithie.
Parent Unit: Strathmore Group (SEG)
Previous Name(s): Edzell Mudstone Formation [Obsolete Name And Code: See CXF] (EDM)
Edzell Mudstones (-3342)
Laurencekirk Mudstone Formation [Obsolete Name And Code: See CXF] (LKMU)
Cromlix Formation (-2133)
Alternative Name(s): Sannox Siltstones
Stratotypes:
Reference Section  Banks of River Almond, Almondbank. 
Reference Section  Exposure showing interfingering with former Edzell Sandstone Formation and Strathfinella Hill Conglomerate, banks of Shag Burn, Auchenblae, 
Partial Type Section  Banks of Bullie Burn, Braco. 
Reference(s):
Carroll, S, 1995. Geology of the Auchenblae District. British Geological Survey Technical Report. WA/95/80. 
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. 
Francis, E H, Forsyth, I H, Read, W A and Armstrong, M. 1970. The geology of the Stirling district. Memoir of the Geological Survey of Great Britain, Sheet 39 (Scotland). 
Friend, P F, Harland, W B and Hudson, J D, 1963. The Old Red Sandstone and the Highland Boundary in Arran, Scotland. Transactions of the Edinburgh Geological Society, Vol.19, 363-425. 
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. 
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 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S066 S038 S048 S048 S056 S066 S030 S038 S039 S039 S047