The BGS Lexicon of Named Rock Units — Result Details

Down Cliff Clay Member

Computer Code: DCC Preferred Map Code: notEntered
Status Code: Full
Age range: Toarcian Age (JT) — Toarcian Age (JT)
Lithological Description: Grey, calcareous, bioturbated silicate mudstones, locally very finely sandy and micaceous, which generally increases upwards. In upper part, beds up to 0.5m thick of pale grey calcareous very fine-grained silicate-sandstone or finely sandy limestone occur. Fauna includes ammonites.
Definition of Lower Boundary: Base probably a non-sequence: sandy mudstone resting sharply on fossiliferous fine limestones of the Beacon Limestone Formation.
Definition of Upper Boundary: Top is marked by the change up from sandy mudstone to sands or sandstones of the undivided Bridport Sand Formation.
Thickness: Dorset coast: 10 to 21m. Inland Dorset: 0 to 121m (Bristow et al., 1995). East Somerset up to 12m.
Geographical Limits: Dorset from Bridport to Shaftsbury; Shepton Mallet area of east Somerset.
Parent Unit: Bridport Sand Formation (BDS)
Previous Name(s): Down Cliffs Clay (-1488)
Down Cliff Clay (-204)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Coastal cliffs from Ridge (Down) Cliff to Thorncombe Beacon, Bridport, Dorset. Fully exposed but poorly accessible in upper part of cliffs. Hesselbo and Jenkyns, 1995, fig.16. 
Reference Section  East Cliff, West Bay, Dorset. Uppermost 4m visible and accessible. Hesselbo and Jenkyns, 1995. p.123, fig.16. 
Reference(s):
Callomon, J H and Cope, J C W. 1995. The Jurassic geology of Dorset. 51-103 in Taylor, P D (Editor), Field Geology of the British Jurassic. (Bath: The Geological Society.) 
Buckman, S S, 1922. Jurassic Chronology: II - Preliminary studies. Certain Jurassic strata near Eypesmouth (Dorset): the Junction-Bed of Watton Cliff and associated rocks. Quarterly Journal of the Geological Society of London, Vol.78, 378-436. 
Hesselbo, S P and Jenkyns, H C A, 1995. A comparison of the Hettangian to Bajocian successions of Dorset and Yorkshire. 105-150 in Taylor, P D (Editor). Field geology of the British Jurassic (London Geological Society). 
Arkell W J, 1933. The Jurassic System in Great Britain [Oxford: Clarendon Press.] 
Cox, B M, Sumbler, M G and Ivimey-Cook, H C, 1999. A Formational framework for the Lower Jurassic of England and Wales (Onshore Area). British Geological Survey Research Report No. RR/99/01. 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M and Woods, M A. 1999. The Wincanton district - a concise account of the geology. Memoir of the British Geological Survey, Sheet 297 (England and Wales). 
Wilson, V, Welch, F B A, Robbie, J A, and Green, G W. 1958. Geology of the country around Bridport and Yeovil. Memoir of the Geological Survey of Great Britain, Sheets 327 and 312 (England and Wales). 
Bristow, C R, Barton, C M, Freshney, E C, Wood, C J, Evans, D J, Cox, B M, Ivimey-Cook, H C, and Taylor, R T. 1995. Geology of the country around Shaftesbury. Memoir of the British Geological Survey, Sheet 313 (England and Wales). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E327 E341 E342 E343 E280 E297