The BGS Lexicon of Named Rock Units — Result Details

BRIDPORT SAND FORMATION
Computer Code: BDS  Status Code: FORMAL, NATIONAL 
Preferred Map Code: BdS 
Age or Age Range: [ JT ] TOARCIAN  to [  ]  
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: Parent Unit Code:
LIAS GROUP  LI
Previous Name(s): Previous Code(s):
MIDFORD SAND(S)   
COTSWOLD SANDS   
YEOVIL SANDS   
COTTESWOLD SANDS   
BRIDPORT AND YEOVIL SANDS   
BRIDPORT SANDS   
UPPER LIAS SANDS   
Alternative Name(s):
none recorded or not applicable
Stratotypes:
Type Area  Broadwindsor to Burton Bradstock, Dorset. 
Reference Section  British Geological Survey Winterborne Kingston Borehole, Winterborne Kingston, Dorset (SY89NW/1) 927.89-1114.60m depth. 
Type Section  Coastal cliff exposures (East Cliff and Burton Cliff) between West Bay and Burton Bradstock, Dorset. 
Reference(s):
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. 
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. 
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. 
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). 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
Map Code Sheet Name
E  297
E  327
E  251
E  234
E  312
E  264
E  265
E  281
E  235
E  252
E  217
E  280
E  343
E  341
E  342

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