Groups and Networks

Britain offers some of the finest sections of Lower Carboniferous (Mississipian) strata in western Europe and has been at the forefront of Lower Carboniferous stratigraphical research since the first biostratigraphical zonation schemes were established by Vaughan, Garwood and Bisat in the earlier part of the 20th century. The British Lower Carboniferous is economically important for its supply of limestones and mudrocks to the construction industry.

Lower Carboniferous sedimentation is dominated by marine deposits, certainly until the beginning of the Serpukhovian (earliest Namurian), when, uplift of northern source areas led to southwards progradation of clastic delta complex which rapidly filled the British basinal areas during the Namurian. Lower Carboniferous sedimentation is sub-divided into areas undergoing slow subsidence and thus accommodating a relatively thin Lower Carboniferous succession (variously called ‘blocks’, ‘highs’, ‘shelves’ or ‘platforms’) and areas undergoing more rapid subsidence ( ‘basins’, ‘troughs’, ‘gulfs’ or ‘lows’). South of the Wales–Brabant Massif, the Culm Trough and the shelf area bordering it are remnants of a back-arc basin relating to northwards subduction and closure of the Rheic Ocean. The Midland Valley in Scotland, is a major rift between the Grampian Mountains to the north and the Southern Uplands to the south. In late Visean times, uplift of northern source areas led to southwards progradation of clastic delta complex which rapidly filled the British basinal areas. At this time, active rifting largely ceased and regional subsidence occurred.

The Lower Carboniferous is divided into eight regional British stages, six in the Tournaisian to Visean (Courceyan, Chadian, Arundian, Holkerian, Asbian and Brigantian) and two in the Serpukhovian (Pendleian and Arnsbergian in the Namurian). These are sub-divided and defined on the basis of ammonoids, corals, conodonts, foraminifera and miospores.

There is a broad underlying pattern of lithofacies development which is recognizable, as follows.

1. Inverclyde Group: predominantly fluvial to peritidal deposits with calcrete development indicative of an arid to semi-arid climate. The group is developed in the Midland Valley of Scotland and Northumberland Trough of northern England. An equivalent lithofacies is developed in the Stainmore Trough, where it is named the Ravenstonedale Group.
2. Strathclyde Group: mainly fluvial, deltaic and lacustrine deposits, the latter including the West Lothian Oil Shale Formation. The group, present within the Midland Valley of Scotland, is laterally associated with a thick volcanic succession. The lithofacies also extends into the Northumberland Trough as the Lyne Formation (Border Group). Good excursion guides to many Scottish sites can be found on earthwise.
3. Carboniferous Limestone Supergroup: ramp to shelf carbonates developed on depositional highs associated with low subsidence rates (component groups: Pembroke Limestone of South Wales and Bristol/Mendips; Clwyd Limestone of North Wales; Peak Limestone of central England; Great Scar Limestone of northern England.
4. Yoredale Group: marine shales and limestones and interbedded marine, deltaic and fluvial sandstones, found in northern England (Component formations: Tyne Limestone, Alston and Stainmore). In the Midland Valley of Scotland, the equivalent succession is represented by the Clackmannan Group, with deltaic sandstones and volcanogenic deposits of Namurian to basal Westphalian (component formations: Limestone Coal, Upper Limestone and Passage).
5. Craven Group: mainly basinal shales with subordinate turbidite deposits (Component formation: Bowland Shale).In the Culm Trough an equivalent basinal shale succession is developed as the Teign Valley Group, associated with deeper marine conditions including development of radiolarian cherts.  

(extracts adapted from Cossey et al. 2004 and Waters et al. 2007). 

Further Information

Cossey, P.J., Adams, A.E., Purnell, M.A., Whiteley, M.J., Whyte, M.A. & Wright, V.P., (2004). British Lower Carboniferous Stratigraphy , Geological Conservation Review Series, No. 29, Joint Nature Conservation Committee, Peterborough, 617pp.

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/10/07.

Waters, C N, Somerville, I D, Jones, N S, Cleal, C J, Collinson, J D, Waters, R A, Besly, B M, Dean, M T, Stephenson, M H, Davies, J R, Freshney, E C, Jackson, D I, Mitchell, W I, Powell, J H, Barclay, W J, Browne, M A E, Leveridge, B E, Long, S L, And Mclean, D. (2011). A Revised Correlation of Carboniferous Rocks in the British Isles . Special Report No. 26. London: The Geological Society.

Waters, C N, Waters, R A, Barclay, W J, And Davies, J R. (2009). Lithostratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore) . British Geological Survey Research Report, RR/09/01.

Waters, C.N. Browne, M.A.E., Dean, M.T., & Powell, J.H. (2007). Lithostratigraphical framework for the Carboniferous successions of Great Britain (onshore) . BGS research report RR/07/01.