The BGS Lexicon of Named Rock Units — Result Details

Lonan Formation

Computer Code: LNN Preferred Map Code: notEntered
Status Code: Full
Age range: Tremadoc Series (O1) — Arenig Series (OR)
Lithological Description: A pale to dark grey mudstone, with a variable proportion of siltstone in laminae to thin beds, and sandstone in thin to medium beds becoming locally dominant.
Definition of Lower Boundary: Not seen, but probably faulted.
Definition of Upper Boundary: In stratigraphical contact with the Mull Hill and Creg Agneash Formations, and marked by a change from a mudstone- to a sandstone-dominated facies.
Thickness: At least 2,500 m thick.
Geographical Limits: Isle of Man.
Parent Unit: Manx Group (MANX)
Previous Name(s): Lonan And Niarbyl Flags (-2206)
Lonan Flags [Obsolete Name And Code: See LNN] (LONF)
Parts Port Erin Formation, Santon Formation, Ny Garvain Formation (-372)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Laxey Bay. Woodcock et al., 1999. 
Reference(s):
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 
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. 
Geological Survey. 1898. Isle of Man. Sheet 36,45,46 and 57. Solid and Drift geology. 1:63 360 scale. Reprinted at 1:50 000 scale by Institute of Geological Sciences 1975 (Southampton: Ordnance Survey). 
Simpson A. 1963. The stratigraphy and tectonics of the Manx Slate Series. Quarterly Journal of the Geological Society of London, Vol. 119, 367-400 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E400