The BGS Lexicon of Named Rock Units — Result Details

Tweed Catchments Subgroup

Computer Code: TWEED Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Holocene Epoch (QH)
Lithological Description: A suite of fluvial, lacustrine, mass movement (head), periglacial and organic (peat) deposits. The subgroup includes the alluvium and river terrace deposits of the River Tweed and tributaries (Tweed Valley Formation). The fluvial deposits contain clasts derived from rocks cropping out within the catchment of the River Tweed in northern Northumberland and the Scottish Borders (mainly Devonian to Carboniferous sandstone, siltstone with limestone, Lower Palaeozoic wacke sandstone and siltstone and varying proportions of volcanic rocks including Devonian andesites of the Cheviot Hills and Carboniferous basalts of the Kelso district).
Definition of Lower Boundary: Unconformable contact with units of the Borders Glacigenic Subgroup and Southern Uplands Glacigenic Subgroup, and with bedrock.
Definition of Upper Boundary: Generally the ground surface, but units of this subgroup locally interfinger with units of the Great Britain Coastal Deposits Group.
Thickness: Generally less than 5m. Individual terrace deposits up to 5m.
Geographical Limits: The catchment of the River Tweed in northern Northumberland and the Scottish Borders including the northern drainage of the Cheviot Hills, the valley of the River Till, Teviotdale, Ettrick, Yarrow and Tweed valleys, and southern drainage of the Lammermuir Hills.
Parent Unit: Britannia Catchments Group (BCAT)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The catchment of the River Tweed in northern Northumberland and the Scottish Borders including the northern drainage of the Cheviot Hills, the valley of the River Till, Teviotdale, Ettrick, Yarrow and Tweed valleys, and southern drainage of the Lammermuir Hills. See also stratotypes of constituent formations. 
Reference(s):
Mitchell, W A. 2005. A reconnaisance of the superficial deposits of the Kale Water, Cheviot Hills, Roxburghshire. British Geological Survey Internal Report IR/05/163. 
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