The BGS Lexicon of Named Rock Units — Result Details

Ormskirk Sandstone Formation [Obsolete Name And Code Use: HEY]

Computer Code: OMS Preferred Map Code: OmS
Status Code: Index Level
Age range: Early Triassic Epoch (TE) — Early Triassic Epoch (TE)
Lithological Description: Fine- to coarse-grained (generally medium-) cross bedded and flat bedded sandstones, generally friable. In West Cumbria sandstones are aeolian, but offshore the Ormskirk Sandstone is dominated by fluvial sandstones, with aeolian interbeds. Details of lithology in the type area are not known, other than a description of 'coarse sandstone'.
Definition of Lower Boundary: In the Reference Section (Sellafield Bh 13B), it is taken where aeolian sandstones overlie a thick fluvial sandstone sequence assigned to the Calder Sandstone. Geophysically, it is marked by a rapid upward decrease in gamma-ray values and an increase in sonic interval transit times.
Definition of Upper Boundary: Not seen onshore in West Cumbria, offshore it is overlain by the Mercia Mudstone Group. Awaits formal definition offshore in East Irish Sea Basin.
Thickness: 176.42m+ onshore in Cumbria. Average 250m elsewhere. Up to 275m offshore.
Geographical Limits: Sellafield to Drigg on West Cumbrian coast; East Irish Sea Basin (offshore). Parts of North Lancashire in the same basin.
Parent Unit: none recorded or not applicable
Previous Name(s): Lower Keuper Sandstone [Obsolete Name And Code: Use HEY] (LKS)
Ormskirk Sandstone (-1104)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Sellafield Borehole 13B, BGS Registered No. NY00SW/42, from 35.97 - 176.42m. 
Type Area  Ormskirk area, Lancashire. 
Reference(s):
Barnes, R P, Ambrose, K, Holliday, D W, and Jones N S. 1994. Lithostratigraphical subdivision of the Triassic Sherwood Sandstone Group in west Cumbria. Proceedings of the Yorkshire Geological Society, Vol. 50, 51-60. 
Warrington, G, Audley-Charles, M G, Elliott, R E, Evans, W B, Ivimey-Cook, H C, Kent, P E, Robinson, P L, Shotton, F W and Taylor, F M. 1980. A correlation of the Triassic rocks in the British Isles. Special Report of the Geological Society of London, No.13. 
Ambrose, K, Hough, E, Smith, N J P and Warrington, G. 2014. Lithostratigraphy of the Sherwood Sandstone Group of England, Wales and south-west Scotland. British Geological Survey Research Report, RR/14/01. 
Jackson, D I, Mulholland, P, Jones, S M and Warrington, G, 1987. The geological framework of the East Irish Sea Basin. 191-203 in Brooks J and Glennie, K (editors), Petroleum Geology of North West Europe. [Graham and Trotman.] 
Institute of Geological Sciences, 1977.1:50.000 Geological Sheet 84 (Wigan) 
Howard, A S, Warrington, G, Ambrose, K, and Rees, J G. 2008. A formational framework for the Mercia Mudstone Group (Triassic) of England and Wales. British Geological Survey Research Report, RR/08/04. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E084 E047 E037