Balladoole Formation is part of the Great Scar Limestone Group
The formation comprises limestone, with interbedded subordinate claystone and siltstone at the top. The limestones are typically grey, contain crinoids, brachiopods and corals, and are locally dolomitic. They vary from grainstone to packstone, with bioherms of wackestone. Large bioherms have been described, up to 5 m in height and 10 m in width.
The formation represents carbonate platform edge deposits.
A partial type section is poorly exposed along the foreshore adjacent to Balladoole Quarry from Poyll Ritchie (SC 2400 6810) to Salt Spring Cottage (SC 2440 6790). Due to faulting the base of the formation is not exposed at Balladoole, but the top of the formation is seen below Salt Spring Cottage where it comprises unbedded lime-mud mounds overlain by a series of well-bedded skeletal limestones, intercalated with soft, fissile shales (see Dickson et al., 1987).
Lower and upper boundaries
See Figure 8, Column 8. The base of the formation is poorly defined and thought to be diachronous. It is partly coeval with the Bowland Shale Formation, Craven Group and was subsequently overstepped by it (Chadwick et al. 2001). At Sea Mount (SC 2590 6990) in Castletown Bay the Balladoole Formation rests directly on the nodular, cherty wackestone with scattered thin claystone layers of the Hodderense Limestone Formation (Craven Group).
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 (SC 2440 6790). Here the Balladoole Formation comprises unbedded lime mud mounds, and the overlying Bowland Shale Formation comprises detrital carbonates, with interbedded grey mudstones and debris beds, including erosively based, graded packstone beds.
The formation is about 90 m thick.
Distribution and regional correlation
The southern part of the Isle of Man, in the Castletown area.
- Chadwick, R A, Jackson, D I, Barnes, R P, Kimbell, G S, Johnson, H, Chiverrell, 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.The 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, Vol. 86, 234–290.
- Dickson, J A D, Ford, T D, and Swift, A.1987.The strati-graphy of the Carboniferous rocks around Castletown, Isle of Man.Proceedings of the Yorkshire Geological Society, Vol. 46, 203–229.