The BGS Lexicon of Named Rock Units — Result Details

Drumbeg Sand And Gravel Formation

Computer Code: DRBG Preferred Map Code: DRBG
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: The standard section is contained in the Gartness Borehole (Browne and McMillan, 1989, Figure 7), 0.5 to 10.17m depth. The two typical lithological associations of the formation are fine- to locally medium-grained sand with silt layers, and silt with sand and clay layers. The sediments are reddish brown or orange. Derived marine fossils are present in the sediments. Pebbly layers are present at the top as are rare bands of diamicton up to 4cm thick. When faulting is present any adjacent bands of clay are usually sheared and contain striaited polished surfaces. The lithofacies association of the formation are typical of a deltaic environment of deposition in contact with active and decaying glacier ice.
Definition of Lower Boundary: Unconformity on bedrock or most commonly on older Quaternary strata including the Clyde Clay Formation and the Wilderness and Gartocharn Till Formation of the Midland Valley Glacigenic Subgroup. It has complex lateral relationships with the Blane Water Silt Formation into which it both grades and also is thrust laterally by glaciotectonic effects at the terminus of the Loch Lomond Stadial Ice Sheet. It also has complex contacts with the Gartocharn Till Formation for the same reason (Phillips et al., 2002).
Definition of Upper Boundary: Unconformity below younger Quaternary strata such as the Clydebank Clay Formation but also exposed at the surface.
Thickness: Veneer to about 25m
Geographical Limits: Central Scotland; Glasgow area, Stirlingshire near, at and within the limits of the Loch Lomond Stade Ice Sheet in the Endrick, Blane and Leven valleys.
Parent Unit: Midland Valley Glacigenic Subgroup (MVG)
Previous Name(s): Drumbeg Formation (-4005)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  British Geological Survey Gartness Borehole (Registered No. NS48NE/2) Browne and McMillan, 1989a, b. 
Partial Type Section  Drumbeg Sand and Gravel Pit, Drymen. Phillips et al. 2002. 
Reference(s):
Browne, M A E and McMillan, A A. 1989a. Quaternary geology of the Clyde valley. British Geological Survey Research Report, SA/89/1. 
Phillips, E R, Evans, D J A and Auton, C A. 2002. Polyphase deformation at an oscillating ice margin following the Loch Lomond Readvance, central Scotland, UK. Sedimentary Geology, Vol.149, 157-182. 
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. 
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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S030 S030 S038