The BGS Lexicon of Named Rock Units — Result Details

Inverclyde Group

Computer Code: INV Preferred Map Code: INV
Status Code: Full
Age range: Courceyan Substage (CF) — Chadian Substage (CI)
Lithological Description: The Inverclyde Group (Paterson and Hall, 1986) represents continental and peritidal facies. In the Midland Valley of Scotland it comprises, in ascending order, the Kinnesswood, Ballagan and Clyde Sandstone formations. In Northern England, in the Berwick area and Solway Basin, the Kinnesswood and Ballagan formations are separated by the Kelso and Birrenswark Volcanic formations respectively (see Greig, 1988 and Lumsden et al., 1967). There is no equivalent to the Clyde Sandstone Formation of the Midland Valley of Scotland in the Northern England Province. The group is characterised by sandstones with pedogenic carbonate (continental fluvial clastic 'cornstone' subfacies) and by silty mudstones containing thin beds of dolostone and limestone (peritidal marine and evaporite 'cementstone' subfacies). There may be some lateral passage of the two subfacies. Tournaisian (Famennian? to Chadian) in age. The continental fluvial clastic 'cornstone' subfacies represents alluvial fan, fluvial channel and floodplain overbank, deposited in a semi-arid climate. The peritidal marine and evaporite 'cementstone' subfacies represents alluvial plain and marginal marine flats subject to periodic desiccation and fluctuating salinity, in a semi-arid climate (Waters et al., 2007).
Definition of Lower Boundary: In the Midland Valley of Scotland, the base of the group is taken at the base of the Kinnesswood Formation where the dominantly sandstone lithologies of the underlying Stratheden Group (Late Devonian: defined by Paterson and Hall, 1986) are succeeded by pedogenic carbonate-bearing strata. Typically transitional, the base is locally defined by an unconformity in the west of the Midland Valley. In Northern England the base of the group is taken where Silurian strata (greywackes with interbedded mudstones) of the Riccarton Group are succeeded unconformably by red sandstones, siltstones and conglomerates of the Kinnesswood Formation.
Definition of Upper Boundary: In the Midland Valley of Scotland, the base of the Strathclyde Group (heterolithic clastic and nonmarine carbonate facies) defines the top of the Inverclyde Group, and the youngest formation, the Clyde Sandstone Formation, that itself represents a return to fluviatile pedogenic facies similar to the basal Kinnesswood Formation. In Northern England, the base of the Border Group (heterolithic clastic and nonmarine carbonate facies and fluviodeltaic 'Millstone Grit' facies) defines the top of the group.
Thickness: In the Midland Valley of Scotland, the Inverclyde Group is about 1500 m thick. It is up to 900 m thick in the Tweed Valley, Northumberland, and up to 640 m thick in the Solway Firth area.
Geographical Limits: The type area of the Inverclyde Group is Greenock, Inverclyde District (see Paterson and Hall, 1986). In Scotland, the group extends across the Midland Valley and occurs at Machrihanish and on Arran, the Cumbrae isles and Bute and Cowal. It also extends across and along the southern margin of the Southern Uplands Terrane from Eyemouth to Dalbeattie. In Northern England it occurs in the Tweed Valley, Northumberland, and in the Solway Firth area.
Parent Unit: Not Applicable (-)
Previous Name(s): Cementstone Group [Obsolete Name and Code: Use BGN, TYN, INV] (*172)
Cementstone Group (B) [Obsolete Name and Code: Use INV, BGN, CMNT] (CMST)
Cementstone Group (A) [Obsolete Name and Code: Use INV, BGN, CMNT] (CST)
Stirling Group [Obsolete Name and Code: Use INV] (SLG)
Calciferous Sandstone Measures [Obsolete Name and Code: Use INV, SYG] (CSM)
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
Paterson, I B and Hall, I H S. 1986. Lithostratigraphy of the late Devonian and early Carboniferous rocks in the Midland Valley of Scotland. British Geological Survey Report, 18/3. 
Dean, M T, Browne, M A E, Waters, C N and Powell, J H. 2011. A lithostratigraphical framework for the Carboniferous successions of northern Great Britain (onshore). British Geological Survey Research Report, RR/10/007. 165pp. 
Greig, D C. 1988. Geology of the Eyemouth district. Memoir of the British Geological Survey, Sheet 34 (Scotland). 
Lumsden G I, Tulloch W, Howells M F and Davies A. 1967. The geology of the neighbourhood of Langholm. Memoir of the Geological Survey, Sheet 11 (Scotland). 
Waters, C N, Browne, M A E, Dean, M T and Powell, J H. 2007. Lithostratigraphical framework for Carboniferous successions of Great Britain (Onshore). British Geological Survey Research Report, RR/07/01. 
Waters, C N, Gillespie, M R, Smith, K, Auton, C A, Floyd, J D, Leslie, A G, Millward, D, Mitchell, W I, McMillan, A A, Stone, P, Barron, A J M, Dean, M T, Hopson, P M, Krabbendam, M, Browne, M A E, Stephenson, D, Akhurst, M C, and Barnes, R P. 2007. Stratigraphical Chart of the United Kingdom: Northern Britain. (British Geological Survey.) 
MacGregor, A G, 1960. Division of the Carboniferous on Geological Survey Scottish Maps. Bulletin of the Geological Survey of Great Britain, No.16, 127-130. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S029 S012 S015 S007 S024 S024 S038 S034 S048 S048 S049 E005 S030 S030 S038 S039 S039 S040