The BGS Lexicon of Named Rock Units — Result Details

Downton Subgroup

Computer Code: DOW Preferred Map Code: DG
Status Code: Full
Age range: Pridoli Epoch (SO) — Lochkovian Age (DO)
Lithological Description: Sandstone, mudstone, red, green, yellow and purple with thin phosphatic bone bed and tuffs.
Definition of Lower Boundary: Base of siltstone of Ludlow Bone Bed Member (where present) of Downton Castle Sandstone Formation, at sharp, locally scoured junction with underlying flaggy calcareous siltstone of the Whitcliffe Formation (Upper) (formerly Upper Ludlow Shales) (White and Lawson, 1989).
Definition of Upper Boundary: The upper boundary is placed at the top of the Bishop’s Frome (Psammosteus) Limestone, where the mudstone-dominated succession of the underlying Raglan Mudstone Formation is overlain by a succession containing a higher proportion of fluvial sandstones (St Maughans Formation).
Thickness: 342-504m in type area (Main Outcrop of White and Lawson, 1989); ranges up to about 1000 m.
Geographical Limits: Welsh Borderlands and West Midlands; south central and east central Wales.
Parent Unit: Lower Old Red Sandstone Group (LORS)
Previous Name(s): Downton Series (-4617)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Downton Castle Sandstone Formation: Northwest end of old quarry near Downton Castle Bridge, Downton comprising 2.7 m of carbonaceous sandstone, overlain by 3.3 m of thinly bedded micaceous sandstone, passing up gradationally to rubbly shales of the Temeside Mudstone Formation in the southern part of the quarry (Elles and Slater, 1906; White and Lawson, 1989). 
Reference Section  Ledbury Formation: Tributary stream section, south bank of River Teme, east of Downton Castle Bridge, Downton (White and Lawson, 1989). 
Reference Section  Downton Castle Sandstone Formation and Temeside Mudstone Formation: Old quarry in Tin-Mill Wood, south bank of Teme, near Bringewood Forge Bridge, Downton showing 6.7 m of sandstone passing up gradationally into rubbly shales (Elles and Slater, 1906; White and Lawson, 1989). 
Type Area  Ludlow, Shropshire and Downton (see White and Lawson, 1989, for basal stratotype and reference sections). 
Reference Section  Cutting in car park adjacent to the Swan Inn, Munslow Aston, Corve Dale, Shropshire with lowermost 0.9 m of yellow flaggy and fossiliferous sandstone of the Downton Castle Sandstone Formation resting upon 1.0 m of siltstone and silty mudstone with fine-grained sandstone beds of the Ludlow Bone Beds (White and Lawson, 1989; Greig and others, 1968). 
Reference Section  Ledbury Formation: Fishmore Brick Pit, Ludlow, Shrophire (White and Lawson, 1989). 
Partial Type Section  Basal stratotype [Base of Group and Downton Castle Sandstone Formation]. Roadside section, south of junction of Whitecliff Road with main Ludlow to Leominster road, near Ludlow (White and Lawson, 1989). 
Reference Section  Temeside Mudstone Formation and Ledbury Formation: South bank of Teme, near footbridge, east of Ludford Bridge, Ludlow, Shropshire (Elles and Slater, 1906; White and Lawson, 1989). 
Reference Section  Ledbury Formation, top: Devil's Hole stream section, near Morville, Shropshire (White and Lawson, 1989). 
Reference(s):
Bassett, M G, Lawson, J D and White, D E, 1982. The Downton Series as the fourth series of the Silurian System, Lethaia, Vol.15, p.1-24. 
White, D E and Lawson, J D, 1989. The Pridoli Series in the Welsh Borderland and south central Wales. 131-141 in A global standard for the Silurian System. Holland, C H and Bassett, M G (editors) National Museum of Wales, Geological Series No. 9, Cardiff. 
Ball, H W and Dineley, D L, 1961. The Old Red Sandstone of Brown Clee Hill and the adjacent area. Part 1. Stratigraphy. Bulletin of the British Museum (Natural History), Geology Series. [London: British Museum (Natural History).] 177-242. 
Greig D C, Wright, J E, Hains, B A and Mitchell, G H. 1968. Geology of the country around Church Stretton, Craven Arms, Wenlock Edge and Brown Clee. Memoir of the Geological Survey, Sheet 166 (England and Wales). (London: H.M.S.O.). 379pp. 
Elles, G L and Slater, I L, 1906. The highest Silurian rocks of the Ludlow district. Quarterly Journal of the Geological Society of London, 61, 195-221. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable