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
PARTS PORT ERIN FORMATION, SANTON FORMATION, NY GARVAIN FORMATION
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Laxey Bay. 
Reference(s):
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). 
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. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E400