The BGS Lexicon of Named Rock Units — Result Details

Midland Valley Glacigenic Subgroup

Computer Code: MVG Preferred Map Code: MVG
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Suite of glacial, glaciofluvial and glaciolacustrine deposits including sand diamictons (till), sand, gravel, silt and clay. The sediments were deposited by or are the deglaciation products of ice that eminated from the western Grampian Highlands and streamed generally eastwards across the Midland Valley of Scotland. The deposits contain clasts derived predominantly from Carboniferous to Permian sedimentary rocks (sandstone, siltstone, mudstone) and volcanic and intrusive rocks (basalt, microdiorite) of the Midland Valley of Scotland with varying but minor proportions of Dalradian metasedimentary rocks (metasandstone, metapelite) and Caledonian igneous rocks (granite, granodiorite, gabbro). In contrast to the Mearns Glacigenic Subgroup, with red tills dominated by clasts and matrix of Devonian origin of the Strathmore Basin, the Midland Valley Glacigenic Subgroup tills have characteristically grey matrices. However, locally they can be red where the diamictons are derived from red or reddened measures (e.g. Upper Coal Measures, Permian strata, small outcrops of Devonian rocks).
Definition of Lower Boundary: Sharp, unconformable contact with bedrock. Pre-Ipswichian Quaternary deposits are not proven within the Midland Valley of Scotland.
Definition of Upper Boundary: Unconformable contact with unit of the Britannia Catchments Group (Forth Catchments Subgroup, Tay Catchments Subgroup, Clyde Catchments Subgroup) and the British Coastal Deposits Group.
Thickness: To 100m
Geographical Limits: The Midland Valley of Scotland (most of Strathclyde, Stirlingshire, the Lothians and Fife) excluding Arran and the Strathmore Basin south of the Highland Boundary Fault (Aberfoyle, Strathallan and Strathmore districts). Approximately bounded to the south by the line of the Southern Upland Fault. Units of the subgroup may occur locally beyond these geographical boundaries and beyond the approximate surface boundaries with adjacent glacigenic subgroups. Units may also extend offshore (see stratotype classification).
Parent Unit: Caledonia Glacigenic Group (CALI)
Previous Name(s): Sourlie Formation (-1717)
Parts Of Mounthouse Formation Of Sutherland (-4212)
Forth-Teith Formation (-2951)
Parts Of Tayburn Formation (-1076)
Parts Of Clyde Valley Formation (-3570)
Alternative Name(s): none recorded or not applicable
Type Area  Glacigenic deposits of the Midland Valley Glacigenic Subgroup are distributed across the central and southern parts of the Midland Valley of Scotland. Their surface distribution excludes Arran and the Strathmore Basin - see Mearns Glacigenic Subgroup). They rest unconformably on mainly Carboniferous to Permian strata from which they are derived. Units of the subgroup may extend offshore in the Firth of Clyde, Firth of Forth and Firth of Tay. See also stratotypes of constituent formations including the Bailliston Till, Cadder Sand, Broomhill Clay, Wilderness Till, Broomouse Sand and Gravel, Gartocharn Till and Drumbeg Sand and Gravel. Browne and McMillan, 1989a, 1989b. 
Bowen, D Q. 1999. A revised correlation of Quaternary deposits in the British Isles. Geological Society Special Report, No. 23. 
Kirby, R P. 1968. The ground moraines of Midlothian and East Lothian. Scottish Journal of Geology, Vol.4, 209-220. 
Paterson, I B, McAdam, A D and MacPherson, K A T. 1998. Geology of the Hamilton district. Memoir of the British Geological Survey, Sheet 23W (Scotland). 
Browne, M A E and McMillan, A A. 1989b. Geology for land use planning: drift deposits of the Clyde valley Volume 1: Planning Report. British Geological Survey Technical Report, WA/89/78. 
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). 
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). 
Jardine, W G (Editor). 1980. Glasgow Region: Field Guide. [Quaternary Reseach Association.] 
Jardine, W G, Dickson, J H, Haughton, P D W, Harkness, D D, Bowen, D Q and Sykes, G A. 1988. A late Middle Devensian interstadial site at Sourlie, near Irvine, Strathclyde. Scottish Journal of Geology, Vol.24, 288-295. 
Kirby, R P. 1969a. Variation in glacial deposition in a subglacial environment: an example from Midlothian. Scottish Journal of Geology, Vol.5, 49-53. 
Kirkby, R P. 1969b. Till fabric analyses from the Lothians, central Scotland. Geografiska Annaler, Vol.51a, 48-60. 
Browne, M A E and McMillan, A A. 1989a. Quaternary geology of the Clyde valley. British Geological Survey Research Report, SA/89/1. 
McMillan, A A, Hamblin, R J O and Merritt, J W. 2005. An overview of the lithostratigraphical framework for the Quarternary and Neogene deposits of Great Britain (onshore). British Geological Survey Research Report RR/04/04. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable