The BGS Lexicon of Named Rock Units — Result Details

Creggan Moar Mudstone Formation

Computer Code: CRMR Preferred Map Code: notEntered
Status Code: Full
Age range: Arenig Series (OR) — Arenig Series (OR)
Lithological Description: Dark grey mudstone, with laminae of pale siltstone and thin- to medium-bedded quartz arenite sandstone; contains distinctive laminae of manganiferous ironstone. The formation was deposited from low-concentration turbidity flows and as chemical precipitates into oxygenated bottom water conditions (Chadwick et al., 2001, p. 28-29). The mid Arenig pseudoornatum acritarch Biozone is indicated from samples obtained from near the base of the formation. However, samples from Creggan Moar have yielded taxa tentatively taken as indicative of the late Arenig hamata-rarirrugulata Biozone (Chadwick et al., 2001).
Definition of Lower Boundary: The base of the Creggan Moar Mudstone Formation is conformable on the Glen Rushen Mudstone Formation, with the base taken at the incoming of sandstone and manganiferous beds.
Definition of Upper Boundary: Not proved as the formation is faulted against the Niarbyl Formation.
Thickness: About 500 m.
Geographical Limits: Western Isle of Man inland from Peel.
Parent Unit: Manx Group (MANX)
Previous Name(s): Glion Cam Formation [Obsolete Name and Code: Use CRMR, GLDH] (GLMC)
Manx Slate Series [Obsolete Name and Code: Use NBY, CRMR, DALBY, MANX] (-3975)
Maughold Banded Group [Obsolete Name and Code: Use MGD, CGA, CRMR, MHL] (-2687)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Gob ny Gamera [SC 2170 7650]. Woodcock et al., 1999. 
Reference Section  Coast section Fheustal to Niarbyl [SC 2173 7654 to SC 2118 7758]. Woodcock et al., 1999. 
Reference(s):
Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) 
Kennan, P S, and Morris, J H. 1999. Manganiferous ironstones in the early Ordovician Manx Group, Isle of Man: a protolith of coticule. 109-120 in In sight of the Suture: the Palaeozoic geology of the Isle of Man in its Iapetus context. Woodcock, N H, Quirk, D G, Fitches W R, and Barnes, R P (editors). Geological Society of London Special Publication, No. 160. 
Millward, D, and Stone, P. 2012. Stratigraphical framework for the Ordovician and Silurian sedimentary strata of northern England and the Isle of Man. British Geological Survey Research Report, RR/12/04. 119pp. 
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. 
Lamplugh G W. 1903. The geology of the Isle of Man. Memoir Geological Survey of Great Britain. 
Simpson A. 1963. The stratigraphy and tectonics of the Manx Slate Series. Quarterly Journal of the Geological Society of London, Vol. 119, 367-400 
Woodcock N H, Morris J H, Quirk D G, Barnes R P, Burnett D, Fitches W R, Kennan P S and Power G M. 1999. Revised lithostratigraphy of the Manx Group, Isle of Man. 45-68 in 'In sight of the suture' the Palaeozoic geology of the Isle of Man in its lapetus Ocean context. Woodcock N H, Fitches W R, Quirk D G and Barnes R P [editors]. Geological Society of London, Special Publication No. 160. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable