The BGS Lexicon of Named Rock Units — Result Details

Index Limestone (Scotland)

Computer Code: ILS Preferred Map Code: ILS
Status Code: Full
Age range: Pendleian Substage (CE) — Pendleian Substage (CE)
Lithological Description: A pale to dark grey bioclastic (crinoidal) marine limestone, with algal nodules. The name is not geographical in origin, but indicates a marker bed for the Limestone Coal Formation coal seams below.
Definition of Lower Boundary: Generally a conformable change from a marine mudstone almost at the top of the Limestone Coal Formation. The Index Limestone as it is usually called, forms the base of the Upper Limestone Formation.
Definition of Upper Boundary: Generally a conformable change to a thick marine mudstone, which may also include the Huntershill Limestone, that passes up into deltaic arenaceous deposits of the Upper Limestone Formation.
Thickness: From 0.6 m to 2.2m in the Airdrie, Falkirk and Glasgow districts, and 3m in the Irvine area of Ayrshire.
Geographical Limits: Throughout most of the outcrop of the Upper Limestone Formation of the Midland Valley of Scotland, but locally absent in Ayrshire and Strathclyde on highs partly created by the Clyde Plateau Volcanic Formation and poorly developed in central and east Fife because of an on-delta facies change.
Parent Unit: Upper Limestone Formation (ULGS)
Previous Name(s): Index Limestone (*657)
Cowglen Limestone (-1611)
Alternative Name(s): Index Limestone
Stratotypes:
Reference Section  The Mossneuk Borehole, BGS reg. no. NS88NE/204 south of Alloa, with a base at 770m depth, and 0.93m measured thickness. 
Reference(s):
Francis, E H, Forsyth, I H, Read, W A and Armstrong, M. 1970. The geology of the Stirling district. Memoir of the Geological Survey of Great Britain, Sheet 39 (Scotland). 
Monro, S K. 1999. Geology of the Irvine District. Memoir of the British Geological Survey, Sheet 22W and part of 21E (Scotland). 
Hinxman, L W, Anderson, E M and Carruthers, R G. 1920. The economic geology of the Central Coalfield of Scotland, Area IV; Paisley, Barrhead, Renfrew. Memoir of the Geological Survey, Scotland. 
Hall, I H S, Browne, M A E and Forsyth, I H. 1998. Geology of the Glasgow district. Memoir of the British Geological Survey, Sheet 30E (Scotland). 
Cameron, I B, Aitken, A M, Browne, M A E and Stephenson, D. 1998. Geology of Falkirk District. Memoir of the British Geological Survey Sheet 31E (Scotland). 
Forsyth, I H, Hall, I H S and McMillan, A A. 1996. Geology of the Aidrie district. Memoir of the British Geological Survey, Sheet 31W (Scotland). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S015 S023 S013 S031 S031 S025 S024 S015 S338 S014 S023 S024 S033 S032 S032 S040 S030 S039 S039