The BGS Lexicon of Named Rock Units — Result Details

Downend Member

Computer Code: DN Preferred Map Code: notEntered
Status Code: Full
Age range: Bolsovian Substage (CC) — Bolsovian Substage (CC)
Lithological Description: Sandstone with some conglomerate and pebbly sandstone and sporadic fissile mudstone beds. Some workable coal seams are also present. Sandstone is typically a coarse-grained lithic arenite of "Pennant" type
Definition of Lower Boundary: Base of member is the base of the lowest mappable lithic sandstone of "Pennant" type above the grey and red mudstone-dominated succession of the Winterbourne Formation. The base is diachronous; In the Somerset Coalfield the base of the member occurs between the Aegiranum and Cambriense Marine Beds, wheras in the Bristol Coalfield it occurs above the Cambriense Marine Band
Definition of Upper Boundary: The top of the Downend Member is defined at the top of the Mangotsfield Coal and associated thin fissile mudstone, overlain by the sandstone-dominated succession of the Mangotsfield
Thickness: 660m in the Somerset Coalfield [ST75]
Geographical Limits: Bristol and Somerset Coalfields
Parent Unit: Pennant Sandstone Formation (PES)
Previous Name(s): Downend Formation (-4001)
Downend Group (*144)
Alternative Name(s): Downend Group
Stratotypes:
Reference Section  The sandstone quarry at Frenchay Bridge [ST639 771]: about 30m of massive sandstone, from below the stinking Coal [NE Bristol] (Kellaway and Welch, 1993] 
Type Area  Downend, Avon (ST6577), the sandstone quarry at Frenchay Bridge (ST639771) and Harry Stoke C (Downend) borehole (ST67NE/1) (ST65047677) from 10.4 m to 317.1 m. 
Reference(s):
Kellaway, G A and Welch, F B A, 1993. Geology of the Bristol district. Memoir of the British Geological Survey Special Sheet [England and Wales]. 
Kellaway, G A. 1969. The Upper Coal Measures of South-West England compared with those of South Wales and the Southern Midlands. Compe Rendu 6e Congres Internationale Stratigraphie et Geologie Carbonifere, Sheffield, 1967, Vol. 3, 1039-1055. 
Waters, C N, Barclay, W J, Davies, J R and Waters, R A. In press. Stratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/05/06. 
Harry Stoke C (Downend) borehole[ST67NE/1] [ST 6504 7677] from 317.1m to 10.4m [Kellaway and Welch, 1993] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E250 E251 E264 E281 E280