The BGS Lexicon of Named Rock Units — Result Details

Balladoole Formation

Computer Code: BOOL Preferred Map Code: notEntered
Status Code: Full
Age range: Asbian Substage (CR) — Asbian Substage (CR)
Lithological Description: Limestone, with interbedded subordinate claystone and siltstone at the top. Limestones vary from grainstone to packstone with bioherms of wackestone. Locally dolomitic. Limestones are typically grey and contain crinoids, brachiopods and corals. Large bioherms have been described up to 5m in height and 10m in width (Dickson et al.1987). Represents carbonate platform edge deposits.
Definition of Lower Boundary: The base of the formation is poorly defined. The base is thought to be diachronous; it is partly coeval with the Bowland Shale Formation and was subsequently overstepped by it (Chadwick et al.2001). At Sea Mount in Castletown Bay [SC2590 6990] the Balladoole Formation rests directly on the Hodderense Limestone Formation (the former Sea Mount Member of Dickson et al.1987).
Definition of Upper Boundary: The top of the formation is poorly defined. The Bowland Shale Formation oversteps the Balladoole Formation at outcrop in a foreshore exposure north-east of Spring Cottage [SC2440 6790]. Here the Balladoole Formation comprises unbedded lime mud mounds.The overlying Bowland Shale Formation comprises detrital carbonates, with interbedded grey mudstones and debris beds, including erosively based graded packstone beds.
Thickness: c.90m
Geographical Limits: Southern part of the Isle of Man, in the Castletown area, from Balladoole [SC 2417 6785] to Scarlett [SC 2570 6643].
Parent Unit: Great Scar Limestone Group (GSCL)
Previous Name(s): Poyllvaaish Limestones Of Lewis (1930) (-2007)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Balladoole Quarry Dickson et al.(1987) describe incomplete biohermal mounds up to 5m high and 10m wide showing patchy dolomitization. Base not seen, faulted. 
Partial Type Section  Foreshore exposure adjacent to Balladoole Quarry from Poyll Ritchie to Salt Spring Cottage. The top is seen below Salt Spring Cottage where it comprises unbedded lime-mud mounds overlain by well-bedded skeletal limestones, intercalated with soft fissile shales. Dickson et al.(1987) 
Reference(s):
Lamplugh G W. 1903. The geology of the Isle of Man. Memoir Geological Survey of Great Britain 
Dickson, J A D, Ford, T D and Swift, A. 1987. The stratigraphy of the Carboniferous rocks around Castletown, Isle of Man. Proceedings of the Yorkshire Geological Society, Vol.46, 203-229. 
Chadwick, R A, Jackson, D I, Barnes, R P, Kimbell, G S, Johnson, H, Chiverell, R C, Thomas, G S P, Jones, N S, Riley, N J, Pickett, E A, Young, B, Holliday, D W, Ball, D F, Molyneux, S G, Long, D, Power, G M and Roberts, D H. 2001. Geology of the Isle of Man and its offshore area. British Geological Survey Research Report, RR/01/06. 
Lewis, H P. 1930. The Avonian succession in the south of the Isle of Man. Quarterly Journal of the Geological Society of London, 86, 234-290. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E400