The BGS Lexicon of Named Rock Units — Result Details

Langland Till Member

Computer Code: LDTI Preferred Map Code: notEntered
Status Code: Full
Age range: Devensian Stage (QD) — Devensian Stage (QD)
Lithological Description: Generally stiff, structureless, stony, sandy and silty diamict and clayey gravel, characteristically containing abundant Old Red Sandstone clasts (derived from Black Mountain, Fforest Fawr and the Brecon Beacons) and very few Lower Palaeozoic clasts. Subordinate stratified sand and gravel are locally present. Colour and dominant clast composition are variable and generally reflect the local bedrock geology.
Definition of Lower Boundary: At the type locality it unconformably overlies Early Devensian Head deposits or Ipswichian Raised Beach deposits of the Pennard Formation (of Bowen, 1999); elsewhere it is generally unconformable on bedrock or regolith (Barclay et al, 2005).
Definition of Upper Boundary: Generally the ground surface or contact with overlying Late Glacial organic deposits infilling kettleholes (see Bowen, 2005, p.155) (Britannia Catchments Group), or the Kenfig Formation or Wentlooge Level Formation (British Coastal Deposits Group).
Thickness: Highly variable, locally up to 25m (Waters and Lawrence, 1987).
Geographical Limits: Brecon Beacons to Swansea Bay, but excluding the South Wales Coalfield.
Parent Unit: Brecknockshire Glacigenic Formation (BNOCK)
Previous Name(s): Brecknockshire Drift (-4481)
Alternative Name(s): Langland Member
Stratotypes:
Type Section  Coastal section at Rotherslade in Langland Bay exposing 14 m of crudely stratified and well imbricated gravels overlying 3.5m of Early Devensian Head and 0.6m of Raised Baech Deposits of the Pennard Formation (of Bowen, 1999) on bedrock. Campbell and Bowen (1989, p.25-26) 
Reference(s):
Barclay, W J, Davies, J R, Humpage, A J, Waters, R A, Wilby, P R, Williams, M and Wilson, D. 2005. Geology of the Brecon district - a brief explanation of the geological map Sheet 213 Brecon. Sheet explanation of the British Geological Survey. 1:50000 Sheet 213 Brecon. 
Waters, R A and Lawrence, D J D. 1987. Geology of the South Wales Coalfield - Part III: the country around Cardiff. Memoir of the British Geological Survey, Sheet 263. (England and Wales). 
David, J W E, 1883. On the evidence of glacial action in south Brecknockshire and east Glamorgan. Quarterley Journal of the Geological Society, London, Vol.39. 39-54. 
Bowen, D Q. 2005. South Wales. In Lewis, C A and Richards, A E (editors), The glaciations of Wales and adjacent areas. (Logaston Press.) 
Campbell, S and Bowen, D Q. 1989. Quaternary of Wales. Geological Conservation Review. (Peterborough: Nature Conservancy Council.) 
Bowen, D Q, 1999. Wales. Chapter 7 in Bowen, D Q (Editor), A revised correlation of Quaternary deposits in the British Isles. Geological Society of London Special Report, No.23. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable