Difference between revisions of "Scarlett Point Member"
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Scarlett Point Member is part of the Bowland Shale Formation
From Scarlett Point, Isle of Man. Previous names include the Scarlett and Strandhall Beds (Lewis, 1930). The present definition is that of Chadwick et al. (2001); (see also Dickson et al., 1987; Lamplugh, 1903).
The member is characterised by tabular beds of pale wackestone and lime-mudstone. These beds, which can be cherty and pyritous, have gradational (locally dolomitised) boundaries with the subordinate interbedded black fissile, blocky claystones.
Deposition was in a deep marine hemipelagic environment, but with periodic fine clastic and carbonate supply (gravitational).
A partial type section is exposed in coastal sections at Scarlett Point (SC 2570 6620 to 2583 6633) where about 14 m of evenly bedded, pale grey wackestone and lime-mudstone with interbedded black claystone are seen (see Dickson et al., 1987, pp. 214–217; Chadwick et al., 2001, p. 62).
Lower and upper boundaries
The base of the member is taken at the lowest black claystone (about 0.12 m thick) overlying the fine-grained, pale mottled limestone (wackestone) of the Hodderense Limestone Formation at Scarlett Point (SC 2583 6633) (Figure 8, Column 8).
The top of the member is not exposed so the nature of the upper boundary is unknown. The overlying succession comprises black hemipelagic mudstones of the undivided Bowland Shale Formation.
Some 14 m.
Distribution and regional correlation
Southern part of the Isle of Man, in the Castletown area, from Scarlett Point (SC 2583 6633) north-westwards to Poyllvaaish (SC 2440 6761). Visean rocks in the northern part of the island are entirely concealed so it is unknown whether it is present in the north.
Age and biostratigraphical characterisation
Asbian. Chondritiform and Helminthoides burrows are common in the limestones. Inadunate crinoid lags and scattered ammonoids of genera Beyrichoceras or Bollandoceras also occur, some preserved in semi-buoyant resting position with the venter resting on the former sea bed.
- 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.
- 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
- 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
- Lamplugh, G W.1903.The geology of the Isle of Man.Memoir of the Geological Survey of Great Britain.