The BGS Lexicon of Named Rock Units — Result Details

Ruchill Flagstone Formation

Computer Code: RLF Preferred Map Code: RLF
Status Code: Full
Age range: Early Devonian Epoch (DL) — Early Devonian Epoch (DL)
Lithological Description: Grey to reddish grey, fine- and medium- to locally coarse-grained sandstones with thin interbeds of mudstone and siltstone and the locally impersistent Inchmurrin, Callander Craig and Gartartan conglomeratic members.
Definition of Lower Boundary: In the Callander-Crieff area, taken as the top of the Craig of Monievreckie Conglomerate, which is the volcanic conglomerate of Frances, Forsyth, Read and Armstrong, 1970, south-west of Aberfoyle the Ruchill Formation is faulted against Dalradian and Highland Border Complex rocks.
Definition of Upper Boundary: In the Callender-Crieff area, the top is taken at the base of the Cromlix Mudstone Formation, which is strongly diachronous, whereas in the Aberfoyle area, the Ruchill Flagstone Formation is locally overlain by the Shannochil Sandstone Member of the Cromlix Mudstone Formation.
Thickness: Between 400m and 1750 m thick.
Geographical Limits: The Highland border between Balmaha and Crieff, north-west limb of the Strathmore Syncline.
Parent Unit: Arbuthnott-Garvock Group (ATGK)
Previous Name(s): Ruchill Formation (-3640)
Alternative Name(s): none recorded or not applicable
Type Area  The Callander-Dunblane area of south-west Perthshire, particularly around the Water of Ruchill. Francis et al., 1970. 
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 
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). 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S030 S039 S038 S038 S039 S047