The BGS Lexicon of Named Rock Units — Result Details

Border Group

Computer Code: BDR Preferred Map Code: BDR
Status Code: Full
Age range: Tournaisian Age (CT) — Holkerian Substage (CQ)
Lithological Description: The Border Group (Lumsden et al., 1967; Day, 1970) consists of two sedimentary formations corresponding to some extent to the geographically extended, former Lower and Middle Border groups of Day (1970; see also Waters et al., 2007). The lower, the Lyne Formation (which equates with the 'Cementstones' of older terminology in Northumberland) comprises strata of heterolithic clastic and nonmarine carbonate facies. The Fell Sandstone Formation, of fluviodeltaic ('Millstone Grit') facies, diachronously overlies the Lyne Formation. Thin olivine basalt lavas occur as the Kershopefoot basalts (Williamson in Stephenson et al., 2003). The group is late Tournaisian to Holkerian in age. The heterolithic clastic and nonmarine carbonate facies represents fluviatile, deltaic and lacustrine environments with relatively sparse marine mudstone deposits commonly alternating, in thin cycles. The fluviodeltaic ('Millstone Grit') facies cycles indicate periodic delta progradation with common black mudstone marine bands resulting from marine transgression and delta abandonment (Waters et al., 2007).
Definition of Lower Boundary: The base of the group is conformable where the interbedded sandstones, limestones, anhydrites, rootlet beds and thin coals of the Ballagan Formation (Inverclyde Group) pass upward into the cyclical sequences of sandstone, mudstone and thin limestone of the Lyne Formation. This is the presumption at Bewcastle and Kirkbean, and it has been proved in a borehole at Annandale. The base is also conformable at Brampton where the Ballagan Formation passes upwards into the sandstone-dominated Fell Sandstone Formation. However, in the north-east part of the Northumberland Trough the same boundary is unconformable; and within the central part of the trough, the base of the group has not been proved.
Definition of Upper Boundary: The base of the Yoredale Group (mixed shelf carbonate and deltaic ('Yoredale') facies) defines the top of the Border Group. In Annandale, thick medium- to coarse-grained sandstones, siltstones and seatrocks of the Fell Sandstone Formation of the Border Group are overlain conformably by interbedded sandstone, siltstone and limestone the Tyne Limestone Formation (Yoredale Group). Locally in the Annandale and Langholm districts the base of the Tyne Limestone Formation is represented by interbedded tuffaceous sandstones and siltstones of the Glencartholm Volcanic Beds. In Bewcastle the base of the Tyne Limestone Formation is represented by marine fossiliferous limestone and mudstone of the Clattering Band. In the Clattering Band colonial corals, including Lithostrtion martini and L. portlocki and gigantoproductids (Semiplanus sp.) become common. The upper boundary of the Border Group is diachronous across the Northumberland and Solway basins.
Thickness: The Border Group is greater than 1350 m thick in the central part of the Northumberland Trough.
Geographical Limits: The Border Group is restricted in geographical extent to the Northumberland Trough and Solway Basin.
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
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, 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.) 
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. 
Williamson, I T. 2003. Howford Bridge, east Ayreshire. 166-169 in Stephenson, D, Loughlin, S C, Millward, D, Waters, C N and Williamson, I T, Carboniferous and Permian rocks of Great Britain north of the Variscan Front. Geological Conservation Review Series, No. 27, Joint Nature Conservation Committee, Peterborough. 
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. 
Day, J B W and others, 1970. Geology of the neighbourhood around Bewcastle. Memoir of the British Geological Survey, Sheet 12. (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S011 E012 E020 E023 S017 S006 S017 S034 E005 E001 E002 E013