The BGS Lexicon of Named Rock Units — Result Details

Lias Group

Computer Code: LI Preferred Map Code: Li
Status Code: Full, pending ratification
Age range: Rhaetian Age (TR) — Aalenian Age (JA)
Lithological Description: Predominantly grey, well bedded, marine calcareous mudstone and silty mudstone; thin tabular or nodular beds of argillaceous limestone, particularly in the lower part; thicker units of siltstone and sandstone, particularly in the upper part, and ironstone, particularly in the middle part. Marginal limestone facies also occur.

Offshore, the group comprises dominantly mudstones and argillaceous limestones in four formations: Cerdic Formation, Ida Formation, Offa Formation and Penda Formation.
Definition of Lower Boundary: In some areas, markedly non-sequential on Penarth Group; at base of Blue Lias Formation, Scunthorpe Mudstone Formation or Redcar Mudstone Formation (q.v.).

Offshore the group is defined by the base of the Penda Formation where there is a downward change from hard, thinly bedded argillaceous limestones and mudstones to black, organic-rich mudstones at the top of the Penarth Group.
Definition of Upper Boundary: Commonly an eroded surface at the base of lowest limestone or sandstone of the Inferior Oolite Group, Ravenscar Group or Dogger Formation.

Offshore: Defined by the top of the Cerdic Formation where paralic sandstones and mudstones of the West Sole Group, overlie marine mudstones and sandstones of the Lias Group.
Thickness: To c. 1300 m.

Offshore: Generally less than 300 m, but up to 820 m.
Geographical Limits: Onshore and offshore United Kingdom, including Northern Ireland (see Cope et al., 1980).

Offshore: Southern North Sea Basin (quadrants 35, 40-44, 46-49, 51-52).
Parent Unit: Not Applicable (-)
Previous Name(s): Lias Group (Formerly Lias) (-363)
Lyas (-3524)
Lias (-2903)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  On the north-east Yorkshire coast from Redcar, southwards to Blea Wyke Point. Does not include the base of the Lias Group. 
Reference Section  Felixkirk Borehole. 18.09-299.15m. Includes base of the Lias Group (Report of the Institute of Geological Sciences, 83/11). 
Reference Section  Fulbeck Airfield Borehole F/B5 (SK95SW/17), top to 117.65m depth. 
Reference Section  Copper Hill Borehole, depth 17.31 to 202.11m. 
Reference Section  Dorset coastal sections. Callomon, J H and Cope, J C W, 1995; Hesselbo, S P and Jenkyns, H C, 1995. 
Type Area  North Yorkshire and Cleveland. 
Reference Section  Primary Reference section: North Yorkshire and Cleveland coastal sections. Powell, J H, 1984; Rawson, P F and Wright, J K, 1995; Hesselbo, S P and Jenkyns, H C, 1995. 
Reference(s):
Old, R A, Hamblin, R J O, Ambrose, K and Warrington, G, 1991. Geology of the country around Redditch. Memoir of the British Geological Survey Sheet 183 (England and Wales). 
Townsend, J, 1813. The character of Moses established for veracity as an Historian recording events from the Creation to the Deluge, p.106, 130, 153, 275. Bath and London. 
Phillips, J, 1829. Illustrations of the geology of Yorkshire, p.33. York. 
Strickland, H E and Buckman, J, 1844. "In" Murchison, R I. Outline of the geology of the neighbourhood of Cheltenham. 
Day, E C H, 1863. On the Middle and Upper Lias of the Dorsetshire Coast. Quarterly Journal of the Geological Society of London, Vol.19, 278-297. 
Kellaway, G A and Welch, F B A, 1948. Bristol and Gloucester district, 2nd edition. British Regional Geology. 
Wilson, V and others, 1958. Geology of the country around Bridport and Yeovil. Memoirs of the Geological Survey of Great Britain. 
Cox, B M, Sumbler, M G and Ivimey-Cook, H C, 1999. A Formational framework for the Lower Jurassic of England and Wales. British Geological Survey Research Report No. RR/99/01. 
Callomon, J H and Cope, J C W, 1995. The Jurassic geology of Dorset. 51-103 in Field Geology of the British Jurassic. Taylor, P D (Editor). (Bath: The Geological Society). 
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). 
Rawson, P F and Wright, J K, 1992. The Yorkshire coast. Geologists' Association Guide, No.34. 
Lott, G K and Knox, R W O'B. 1994. 7. Post-Triassic of the Southern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. [British Geological Survey, Nottingham].  
Lott, G K. 1992 Jurassic. In: Cameron, T D J, Crosby, A, Balson, P S, Jeffrey, D J, Lott, G K, Bulat, J and Harrison, D J. United Kingdom offshore regional report: the geology of the southern North Sea. pp.67-79. [HMSO, London, for the British Geological Survey]  
Rastall, R H and Hemingway, J E, 1939. The Blea Wyke Beds and the Dogger at Peak, Yorkshire. Geological Magazine, Vol.76.p.362-372. 
Powell, J H, 1984. Lithostratigraphic nomenclature of the Lias Group in the Yorkshire Basin. Proceedings of the Yorkshire Geological Society, Vol.45, p.51-57. 
Cope, J C W and others, 1980. A correlation of Jurassic rocks in the British Isles. Part 1: Introduction and Lower Jurassic. Special Report of the Geological Society of London, No.14. 
Evans, C D R, 1983. Institute of Geological Science boreholes, 1982. Report of the Institute of Geological Sciences, No.83/11. 
Brandon, A, Sumbler, M G and Ivimey-Cook, H C, 1990. A revised lithostratigraphy for the Lower and Middle Lias (Lower Jurassic) east of Nottingham, England. Proceedings of the Yorkshire Geological Society, Vol.48, 121-141. 
Gaunt, G D, Fletcher, T P amd Wood, C J. 1992. Geology of the country around Kingston upon Hull and Brigg. Memoir of the British Geological Survey, sheets 80 and 89 (England and Wales). 
Rhys, G H, 1974. (Compiler). A proposal standard lithostratigraphic nomenclature for the southern North Sea and an outline structural nomenclature for the whole of the (UK) North Sea. Report of the Institute of Geological Science, No.74/8. 
Woodward, H B, 1893. The Jurassic rocks of Britain. 3. The Lias of England and Wales (Yorkshire excepted). Memoir of the Geological Survey of Great Britain. 
Arkell, W J. 1933. The Jurassic System in Great Britain. [Oxford: Clarendon Press.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E103 E115 E127 E128 S052 E132 E142 E148 E169 E172 E175 E189 E204 E217 E237 E281 E341 E342 E343 E043 E047 E049 E055 E064 E065 E072 E081 E089 E090 E091 N35 S013 S344 S043 S044 S044 S051 S052 S060 S070 S071 S071 S080 S081 S081