The BGS Lexicon of Named Rock Units — Result Details

Shirehampton Formation

Computer Code: SHB Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Courceyan Substage (CF) — Courceyan Substage (CF)
Lithological Description: Interbedded, thin- to medium-bedded red, green and grey mudstone, limestone, sandstone and siltstone with a thick red crinoidal limestone, known as the Bryozoa Bed, developed at the top. Mainly deposited in a marine influenced lagoonal environment.
Definition of Lower Boundary: Gradational, but taken for convenience at the top of the Sneyd Park Fish Bed, a conglomeratic fish-bearing sandstone at the top of the red sandstones, mudstones, siltstones and conglomerates of the underlying Portishead Formation. Above the Sneyd Park Fish Bed grey mudstones and limestones of the Formation appear interbedded with red sandstones and mudstones. This boundary is in need of work.
Definition of Upper Boundary: Taken at the irregular erosive contact between the red crinoidal limestone [Bryozoa Bed] of the Formation and the overlying pebbly phosphatic limestone [Palate Bed], the basal bed of the interbedded limestones and mudstones of the undivided Avon Group.
Thickness: 30 to 50m
Geographical Limits: Bristol area [ST 60 74]. There is considerable confusion over the exact geographical extent. Thought to pass southwards into the undivided Avon Group. Locally included mistakenly within the Portishead Formation on BGS maps.
Parent Unit: Avon Group (AVO)
Previous Name(s): Shirehampton Beds (-1817)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Portway road cutting, 1 km east of Shirehampton church, Bristol. Only the lowermost part of the unit seen, comprising interbedded sandstones, limestones and mudstones. Contact with the underlying Sneyd Park Fish Bed [Portishead Formation] exposed, but the upper contact with the undivided Avon Group is not seen. It is likely that this cutting has become considerably degraded since it was erected as a type section by Kellaway and Welch (1955). 
Reference(s):
Kellaway, G A and Welch, F B A, 1955. The Upper Old Red Sandstone and Lower Carboniferous rocks of the Bristol and the Mendips compared with those of Chepstow and the Forest of Dean. Bulletin of the Geological Survey of Great Britain, No.9, p.1-21. 
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]. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E264