The BGS Lexicon of Named Rock Units — Result Details

Osgodby Formation

Computer Code: OSBY Preferred Map Code: OSY
Status Code: Full
Age range: Callovian Age (JC) — Callovian Age (JC)
Lithological Description: Sandstone, calcareous, and poorly lithified sand; generally massive bedded, greenish-grey, weathering at outcrop to yellow-brown, fine- to medium-grained, with beds of berthierine (chamosite) ooids, calcareous siltstone and thin limestone. Sandstone beds are generally highly bioturbated with horizontal and vertical burrows
Definition of Lower Boundary: Conformable boundary where the soft grey mudstone of the underlying Cayton Clay Formation passes gradationally up to the pale yellow, clayey sandstone of the overlying Osgodby Formation (Redcliff Rock Member). Where the Cayton Clay Formation and the underlying Cornbrash Formation are absent in the Hambleton Hills (in the west of the Cleveland Basin) the Osgodby Formation rests unconformably on non-marine mudstone or sandstone of the Scalby Formation.
Definition of Upper Boundary: Generally a fairly sharp, but conformable junction between the yellow-brown sandstone of the Osgodby Formation (Hackness Rock Member) and the green-grey silicate-mudstone (locally with occasional berthierine ooids) of the overlying Oxford Clay Formation. Locally in the Hambleton Hills, the Oxford Clay Formation and upper part of the Osgodby Formation are absent so that the Lower Calcareous Grit Formation (Oldstead Oolite Member) rests unconformably on the Osgodby Formation (Redcliff Rock Member) (Wright, 1983; Powell et al., 1992, Powell, 2010)
Thickness: Up to 28.5 m on the North Yorkshire Coast (Wright 1968a, Wright, 1978; Rawson and Wright, 2000); thins to c. 20 m in the Hambleton Hills (Powell et al., 1992)
Geographical Limits: Cleveland Basin, Northeast Yorkshire, north of the Market Weighton High.
Parent Unit: Not Applicable (-)
Previous Name(s): Kellaways Rock (Phillips, 1829; Fox-Strangways, 1892) (-1106)
Kellaways Rock Member (Wright, 1978) (-1745)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Osgodby Nab (or Point) [TA 065 854], Cornelian Bay, North Yorkshire (Wright, 1968a,1978; Page 1989; Rawson and Wright 2000; Page in Cox and Sumbler 2002, pp.333-336). Osgodby Point (or Nab) exposes the type section of the Osgodby Formation conformably overlying the Cayton Clay Formation (Wright, 1968a; 1977). All three members are present (compare Red Cliff reference section, below). The Redcliff Rock Member (Page, 1989), 3.5 m thick, comprises red-brown, ferruginous fine-grained sandstone with chamosite (berthierine) ooids; bivalves and the ammonite Kepplerites are present. The overlying Langdale Member, 3.8 m thick, comprises grey-brown, bioturbated, fine-grained sandstone and bioturbated siltstone; the bivalve Gryphaea and decalcified moulds of belemnites are common in the lower part. The overlying Hackness Rock Member, 0.78 m thick, is grey-brown, sandy limestone with abundant chamosite (berthierine) ooids; it is bioturbated and yields bivalves, belemnites and the ammonites Quenstedtoceras and Kosmoceras (Rawson and Wright, 2000). The conformable boundary with the grey-green silty mudstone of the overlying Oxford Clay Formation is clearly seen. 
Reference Section  Red Cliff [TA 076 840] at the southeast end of Cayton Bay, North Yorkshire (Wright, 1968a, pp.371-372) Red Cliff exposes the Redcliff Rock Member, which comprises red-brown, fine-grained sandstone with abundant chamosite (berthierine) ooids; spheroidal carbonate concretions are present in the lower part; bivalves and occasional ammonites (including Kepplerites) are present. The boundary with the underlying Cayton Clay Formation is generally obscured by fallen blocks. At Red Cliff the Langdale Member is absent due to penecontemporaneous erosion (Wright, 1968a). Consequently, the overlying Hackness Rock Member rests disconformably on the Redcliff Rock Member. The Hackness Rock Member comprises grey-brown, bioturbated limestone, 1-2 m thick, with abundant chamosite (berthierine) ooids; it has yielded the ammonites Quenstedtoceras and Kosmoceras (Rawson and Wright, 2000). The conformable boundary with the grey-green, silty mudstone of the overlying Oxford Clay can be seen in the cliff face. 
Reference(s):
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.) 
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Rawson, P F and Wright, J K. 2000. The Yorkshire Coast. Geologists' Association Guide No.34. (London: The Geologists' Association.) 130pp. 3rd Edition. 
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). 
Phillips, J. 1829. Illustrations of the geology of Yorkshire, or a description of the strata and organic remains. Part I, the Yorkshire Coast. (York.) 
Wright, J K. 1983. The Lower Oxfordian (Upper Jurassic) of North Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 44, 249-281. 
Wright, J.K. 1978. The Callovian succession (excluding Cornbrash) in the western and northern parts of the Yorkshire Basin. Proceedings of the Geologists' Association, 89, 259-261. 
Wright, J.K. 1968b. The Callovian succession at Peckondale Hill, Malton, Yorkshire. Proceedings of the Yorkshire Geological Society, 37, 93-97. 
Page, K N. 1989. A stratigraphic revision for the English Lower Callovian. Proceedings of the Geologists' Association, Vol.100, 363-382. 
Wright, J K. 1968a. The stratigraphy of the Callovian Rocks between Newtondale and the Scarborough Coast, Yorkshire. Proceedings of the Geologists' Association, 79, 363-399. 
Powell, J.H. 2010. Jurassic sedimentation in the Cleveland Basin: a review. Proceedings of the Yorkshire Geological Society, 58, 21-72. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E034 E042 E043 E044 E052 E053 E054 E063