The BGS Lexicon of Named Rock Units — Result Details

Tweed Valley Formation

Computer Code: TWVA Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Alluvial,alluvial fan and river terrace gravel, sand, silt and clay. The gravel comprises predominantly Ordovician and Silurian wacke sandstone with Devonian and Carboniferous sandstone, siltstone and a range of basaltic igneous rocks.
Definition of Lower Boundary: A sharp, undulating, erosional contact, mainly on diamictons of the Norham Till Formation (Borders Glacigenic Subgroup) or, in the middle and upper reaches of the Tweed valley, till and glaciofluvial deposits of the Southern Uplands Glacigenic Subgroup.
Definition of Upper Boundary: At the present ground surface or, locally,covered by peat.
Thickness: Up to 10m.
Geographical Limits: The valley of the River Tweed and its tributaries in Peebleshire, Selkirkshire, Roxburghshire, Berwickshire and Northumberland.
Parent Unit: Tweed Catchments Subgroup (TWEED)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Valley of the River Tweed and its tributaries including the Fruid Water, Lyne Water, Manor Water, Leithen Water, Ettrick Water, Gala Water, Leader Water, River Teviot, Whiteadder Water and River Till. 
Reference(s):
Rhind, D W. 1969. The terraces of the Tweed Valley. Unpublished Ph.D Thesis. The Univerity of Edinburgh. 
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. 
Tipping, R. 1998. The chronology of Late Quaternary fluvial activity in part of the Milfield Basin, northeast England. Earth Surface Processes and Landforms, Vol.23, 845-856. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable