The BGS Lexicon of Named Rock Units — Result Details

Ballagan Formation

Computer Code: BGN Preferred Map Code: BGN
Status Code: Full
Age range: Courceyan Substage (CF) — Chadian Substage (CI)
Lithological Description: Grey mudstones and siltstones, with nodules and beds of ferroan dolomite (cementstones), the beds generally less than 0.3m thick. Gypsum and, to a much lesser extent, anhydrite and pseudomorphs after halite occur. Desiccation cracks are common and the rocks commonly show evidence of brecciation during diagenesis. Both these features are associated with reddening of the strata. Where present, the restricted fauna is characterised by the bivalve Modiolus latus, but ostracods are more abundant. Thin sandstones are present in many areas, and thick localised sandstones are also now included in the formation.
Definition of Lower Boundary: Not seen in type section; elsewhere transitional on cornstone-bearing sandstones of Kinnesswood Formation (as at a depth of 224.8m in British Geological Survey East Dron Borehole (NO11NW/24; NO1360 1572)).
Definition of Upper Boundary: The top is drawn at the top of the highest unit of mudstone and cementstone in any particular area. The Clyde Sandstone Formation usually overlies the Formation.
Thickness: About 900m (maximum) in the West Lothian area, and up to 250m in the Northern England Province.
Geographical Limits: Not defined.
Parent Unit: Inverclyde Group (INV)
Previous Name(s): Cementstone Group (A) [Obsolete Name And Code: See INV and BGN; CMNT Offshore] (CST)
Cementstone Group (B) [Obsolete Name And Code: See INV and BGN; CMNT Offshore] (CMST)
Ballagan Cementstone Formation [Obsolete Name And Code: Use BGN] (BNCF)
Border Group, Lower [Obsolete Name And Code: Use BGN Or LYNE] (LBG)
Lower Border Group [Obsolete Name And Code: Use BGN or LYNE] (LBO)
Tyninghame Formation (TYN)
Cementstone Group (*172)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Ballagan Glen 
Partial Type Section  East Dron Borehole [BGS Reg.No. NO11NW/24] 
Type Section  Wall Hill Member, coastal sections, White Port to Port Mary, Kirkcudbrightshire. [Deegan, 1973]. 
Type Section  Orroland Member, coastal section Port Mary to Castle Muir. [Deegan, 1973]. 
Type Section  Kirkbean Member, Kirkbean, Kirkcudbrightshire. Smith and McMillan, 1996. 
Type Section  Whita Sandstone Beds, River Esk between Longwood and Broomholm, Langholm. [Lumsden et al, 1967; Nairn, 1958]. 
Type Section  Annandale Sandstone Beds, River Annan, between Rochell and Hoddom Castle, Ecclefechan. Ssee original Lexicon entry. [Nairn, 1956]. 
Type Section  Kirkbean Member, BGS Hoddom No. 2 Borehole, Ecclefechan. [Craig, 1956; McMillan in: Lintern & Floyd, 2000]. 
Type Section  Whita Sandstone Beds, Tarras Water upstream of Tarras Road Bridge, Langholm. [Lumsden et al, 1967; Leeder, 1974]. 
Reference(s):
Browne, M A E, 1980. The Upper Devonian and Lower Carboniferous (Dinantian) of the Firth of Tay, Scotland. Report of the Institute of Geological Sciences, No. 80/9. 
McMillan, A A. 2000. Upper Palaeozoic in Lintern, B C and Floyd, J D. 2000. Geology of the Kirkcudbright-Dalbeattie District. Memoir of the British Geological Survey, Sheets 5W, 5E and part of 6W (Scotland). 
Browne, M A E, Dean, M T, Hall, I H S, McAdam, A D, Monro, S K and Chisholm, J I. 1996. A lithostratigraphical framework for the Carboniferous rocks of the Midland Valley of Scotland. British Geological Survey Technical Report, WA/96/29. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S048 S015 S023 S013 S031 S338 S026 S033 S032 S032 S033 S034 S048 S049 E004 E006 S030 S030 S038 S039 S039 S040 S041 E008 E001 E013 E014 E002 E003 E005 E009 S005 S005 S006 S010