The BGS Lexicon of Named Rock Units — Result Details

Dodington Ash Rock Member

Computer Code: DASHR Preferred Map Code: DA
Status Code: Full
Age range: Bathonian Age (JN) — Bathonian Age (JN)
Lithological Description: Limestone, pale grey to yellow, fine-grained, muddy, fine- to medium-grained shell detrital, some beds may include ferruginous rounded grains, shelly in places with bivalves, brachiopods, echinoids, gastropods and rare ammonites; basal limestone pebble bed may be present, and succession includes breaks which may be represented by bored and encrusted hardgrounds, indicating a condensed sequence.
Definition of Lower Boundary: Shell-detrital, fine-grained limestone of the Dodington Ash Rock Member with in places a basal pebble bed, sharply overlying grey calcareous mudstone of the Lower Fuller's Earth Member, or where present ooid-limestone of the Minchinhampton Limestone Member.
Definition of Upper Boundary: Shell-detrital, fine-grained limestone of the Dodington Ash Rock Member with in places a burrowed top, sharply overlain by (from south to north) grey calcareous mudstone of the Hawkesbury Clay Member, fine-grained limestone of the Tresham Rock Formation, ooid-limestone of the Athelstan Oolite Formation or White Limestone Formation.
Thickness: At outcrop up to about 3.5m seen. In boreholes generally between 0.7 and 5m, with a maximum of 7.84 m at Tetbury (ST89SE/1)
Geographical Limits: South to Mid Cotswold Hills, Gloucestershire: at outcrop from M4 motorway at Dodington Ash, where it passes south into the Fuller's Earth Rock Member, to Minchinhampton area, where it pinches out north-east. At depth present in boreholes from Atworth, near Melksham to Charlton, near Malmesbury, to Bisley near Stroud.
Parent Unit: Fuller's Earth Formation (FE)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  M4 motorway cutting: member formerly fully exposed, comprising 1.8-2.4m of pink to yellow shell-detrital fine-grained limestone, overlain by about 9m of shelly calcareous mudstone with thin limestone beds of the Fuller's Earth Formation (Hawkesbury Clay Member), and underlain by calcareous mudstone and limestone beds of the Lower Fuller's Earth Member. Torrens, 1968 
Reference Section  Quarry at Woodchester Park Farm (aka Easter Park Farm), Stroud, Gloucestershire. Member possibly fully exposed here as 3.0 to perhaps 3.4m of bedded, ooidal and shelly limestone, on occasions yielding ammonites; underlain by ooid-limestone beds of the Minchinhampton Limestone Member of the Taynton Limestone Formation. Wyatt pp 148-150 in Cox and Sumbler, 2002. See also Cave (1977, p162) where called Cross Hands Rock. 
Reference(s):
Torrens, H S. 1968. Some Fuller's Earth sections in the south Cotswolds. Proceedings of the Bristol Naturalists' Society, Vol. 31, 429-438. 
Barron, A J M, Sheppard, T H, Gallois, R W, Hobbs, P R N, and Smith, N J P. 2011. Geology of the Bath district. British Geological Survey Sheet Explanation, Sheet 265 (England and Wales). 
Cave R. 1977. Geology of the Malmesbury District. Memoir of the Geological Survey of Great Britain, Sheet 251 (England and Wales). 
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Wyatt, R J. 1996. A correlation of the Bathonian (Middle Jurassic) succession between Bath and Burford, and its relation to that near Oxford. Proceedings of the Geologists' Association, Vol. 107, 299-322. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E234 E251 E265