The BGS Lexicon of Named Rock Units — Result Details

Ravenscar Group

Computer Code: RAG Preferred Map Code: RG
Status Code: Full
Age range: Aalenian Age (JA) — Bathonian Age (JN)
Lithological Description: Fluvial, fluvio-deltaic and paralic mudstone, siltstone and sandstone, intercalated with relatively thin marine units comprising calcareous sandstone, calcareous mudstone, calcareous siltstone, limestone and ironstone. Thin coal seams and seatearth mudstones occur in the paralic lithofacies.
Definition of Lower Boundary: The lower boundary is taken at the base of the Saltwick Formation where sandstone, siltstone or mudstone, commonly with plant fragments, rest unconformably or disconformably on the heterolithic, marine, Dogger Formation (ferruginous sandstone; ironstone; limestone; calcareous mudstone) or, where the Dogger Formation is absent, on grey, shelly mudstone or siltstone of the Lias Group.
Definition of Upper Boundary: The upper boundary is taken at the unconformable or disconformable upward passage from sandstones, siltstones and mudstones, commonly with plant fragments, of the Scalby Formation to calcareous, bioturbated mudstone and nodular, shelly limestone of the Cornbrash Formation.
Thickness: Generally about 240m thick on the North Yorkshire coast (Ravenscar to Scarborough) thinning westward to 114m in the Hambleton Hills.
Geographical Limits: The Cleveland Basin, including the North York Moors, Cleveland Hills, Hambleton Hills, Howardian Hills and the North Yorkshire coast. Equivalent strata offshore comprise the West Sole Group (Lott and Knox, 1994).
Parent Unit: Not Applicable (-)
Previous Name(s): Middle Jurassic Series (-4283)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  The type area is the North Yorkshire coast, specifically the Ravenscar area [NZ 985 020] (Versey and Hemingway, 1948; Hemingway and Knox, 1973) for the lower part of the group, up to the base of the Scarborough Formation. The upper part of the group, represented by the strata including the Scarborough Formation and the overlying Scalby Formation is best exposed from Cloughton Wyke [TA 020 950] to Castle Hill [TA 048 893], Scarborough. 
Reference(s):
Lott, G K and Humphreys, B. 1992. The stratigraphy and petrology of Middle Jurassic (Ravenscar Group) sediments in cored boreholes from the North Yorkshire coast. Proceedings of the Yorkshire Geological Society, Vol.49, 23-40. 
Hancock, N J and Fisher, M J. 1981. Middle Jurassic North Sea deltas with particular reference to Yorkshire. 186-195 in Illing, L V and Hobson, G D (eds), Petroleum geology of the continental shelf of north-west Europe. (London: Institute of Petroleum.) 
Hemingway, J E. 1974. Jurassic. 161-233 in Rayner, D H and Hemingway, J E (eds), The geology and mineral resources of Yorkshire. (Leeds: Yorkshire Geological Society.) 
Hemingway, J E and Knox, R W O'B. 1973. Lithostratigraphical nomenclature of the Middle Jurassic strata of the Yorkshire Basin of north-east England. Proceedings of the Yorkshire Geological Society, Vol.39, 527-535. 
Butler, N, Charnock, M A, Hager, K O and Watkins, C A. 2005. The Ravenscar Group: a coeval analogue for the Middle Jurassic reservoirs of the North Sea and offshore Mid-Norway. 43-53 in Powell, A J and Riding, J B (eds), Recent Developments in Applied Biostratigraphy. The Micropalaeontological Society, Special Publications. 
Versey, H C and Hemingway, J E. 1948. Guide to excursion C2, north-east Yorkshire. 19pp. International Geological Congress (18th Session, Great Britain). 
Knox, R W O'B, Howard, A S, Powell, J H and van Buchem, F S P. 1991. Lower and Middle Jurassic sediments of the Cleveland Basin N.E. England: Shallow marine and paralic facies seen in their sequence stratigraphic context. Field Excursion Guide, No.5; 13th International Sedimentological Congress, Nottingham, UK. 1990. 66pp. 
Fox-Strangways, C and Barrow, G, 1915. The geology of the country between Whitby and Scarborough (2nd edition). Memoir of the Geological Survey of the United Kingdom. 
Powell, J H, Cooper, A H C and Benfield, A C. 1992. Geology of the country around Thirsk. Memoir of the British Geological Survey, Sheet 52 (England and Wales). 
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]. 
Rawson, P F and Wright, J K. 1995. Jurassic of the Cleveland Basin, North Yorkshire. 173-208 in Taylor, P D (Ed.) Field Geology of the British Jurassic. (London: Geological Society.) 
Fox-Strangways, C. 1892. Jurassic rocks of Britain, Vols 1 and 2, Yorkshire. Memoir of the Geological Survey of Great Britain. 
Kantorowicz, J D. 1985. Petrology and diagenesis of Middle Jurassic clastic sediments, Ravenscar Group, Yorkshire. Sedimentology, Vol.32, 833-853. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E033 E034 E035 E042 E043 E044 E052 E053 E063 E064