The BGS Lexicon of Named Rock Units — Result Details

Niarbyl Formation

Computer Code: NBY Preferred Map Code: notEntered
Status Code: Full
Age range: Wenlock Epoch (SW) — Wenlock Epoch (SW)
Lithological Description: A thin- to medium-bedded wacke sandstone, interbedded with siltstone and mudstone, locally including laminated carboniferous siltstone and thin beds of meta-bentonite.
Definition of Lower Boundary: The visible contacts are all faulted against Manx Group and the Peel Formation. It is likely that both lower and upper stratigraphical contacts are unconformable - the lower on the Manx Group where distinguished by being sandstone-dominated facies as opposed to mudstone, the upper probably with overlying Permian or Triassic red-bed facies.
Definition of Upper Boundary: Not seen, see above.
Thickness: About 1200 m thick.
Geographical Limits: Isle of Man.
Parent Unit: Dalby Group (DALBY)
Previous Name(s): Manx Slates [Obsolete Name And Code: See MANX] (MXSL)
Niarbyl Flags [Obsolete Name And Code: See NBY] (NBF)
Manx Slate Series (-3975)
Alternative Name(s): none recorded or not applicable
Type Section  The Niarbyl to Glen Maye. Morris et al., 1999 
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. 
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 
Morris J H, Woodcock N H and Howe M P A. 1999. The Silurian succession in the Isle of Man: the late Wenlock Niarbyl Formation, Dalby Group. 189-211 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: