The BGS Lexicon of Named Rock Units — Result Details

Bridport Sand Formation

Computer Code: BDS Preferred Map Code: BdS
Status Code: Full
Age range: Toarcian Age (JT) — Toarcian Age (JT)
Lithological Description: Grey, weathering yellow or brown, micaceous silt, very fine-grained sand and fine-grained sand, locally with calcite-cemented sandstone beds and lenses, variably sandy clay/mudstone at base, including Downcliff Clay [Member] of type area (Knox, R W O'B, Morton, A C and Lott, G K, 1982; Hesselbo, S P and Jenkyns, H C, 1995, and references therein).
Definition of Lower Boundary: Base of sand/silt or mudstone, as described in the Lithological Description, resting non-sequentially on limestone of the Beacon Limestone Formation or, north of c.Chipping Sodbury area in the Worcester Basin, a gradational boundary with mudstone of the Whitby Mudstone Formation (q.v.)
Definition of Upper Boundary: Non sequential; base of lowest limestone (commonly sandy) of the Inferior Oolite Group resting on sand/silt or mudstone (as in the Lithological Description), or on "[Cotswold] Cephalopod Bed" (sandy and argillaceous, ironshot commonly fossiliferous limestone) in the Worcester Basin area.
Thickness: To c.120m
Geographical Limits: Wessex Basin to Worcester Basin (Dorset Coast to central Cotswolds, Cheltenham area).
Parent Unit: Lias Group (LI)
Previous Name(s): COTTESWOLD SANDS
Alternative Name(s): none recorded or not applicable
Type Area  Broadwindsor to Burton Bradstock, Dorset. 
Type Section  Coastal cliff exposures (East Cliff and Burton Cliff) between West Bay and Burton Bradstock, Dorset. 
Reference Section  British Geological Survey Winterborne Kingston Borehole, Winterborne Kingston, Dorset (SY89NW/1) 927.89-1114.60m depth. 
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. 
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). 
Ivimey-Cook, H C, 1982. Biostratigraphy of the Lower Jurassic and Upper Triassic (Rhaetian rocks of the Winterborne Kingston borehole, Dorset). Report of the Institute of Geological Sciences, No.81/3, 97-106. 
Knox, R W O'B, Morton, A C and Lott, G K, 1982. Petrology of the Bridport Sands in the Winterborne Kingston borehole, Dorset. Report of the Institute of Geological Sciences, No.81/3, 107-121. 
Rhys, G H, Lott, G K and Calver, M A (editors), 1982. The Winterborne Kingston borehole, Dorset, England. Report of the Institute of Geological Sciences, No.81/3. 
Wilson, V, et al, 1957. Geology of the country around Bridport and Yeovil. Memoir of the Geological Survey of Great Britian, Sheets 327 and 312. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E234 E235 E251 E265 E281 E297 E312 E327 E217 E252 E280 E341 E342 E343 E264