The BGS Lexicon of Named Rock Units — Result Details

Horsehay Sand Formation

Computer Code: HYSA Preferred Map Code: HS
Status Code: Full
Age range: Bajocian Age (JB) — Bathonian Age (JN)
Lithological Description: Unbedded to weakly bedded and cross-bedded, pale grey and brown to off-white, medium- to fine-grained, quartzose sand, locally cemented into calcareous or weakly ferruginous sandstone with thin dark grey mudstone and siltstone beds in places, rootlets and lignitic debris common, shells and shell debris very rare.
Definition of Lower Boundary: Seen as the passage from lithologically similar sand and sandstone beds with marine shelly fauna, ooidal and shell-detrital limestones of the Northampton Sand Formation (Inferior Oolite Group) where present, or mudstone beds of the Whitby Mudstone Formation (Lias Group) into barren, sand-dominated beds. The non-sequential boundary with the Northampton Sand Formation, may appear conformable or gradational probably as a result of weathering effects, or locally channelled and disconformable [Horton et al. 1987, p.56].
Definition of Upper Boundary: Marked by the presence of mudstones, marls and limestone beds of the Sharp's Hill Formation where present, or ooidal and shell detrital limestones of the Taynton Limestone Formation. The boundary is non-sequential, and may be marked by an eroded or leached and rootleted surface.
Thickness: To 7m
Geographical Limits: Oxfordshire north-east of Sibford Gower, Hook Norton and Tackley [Horton, 1977, fig. 4], where it passes south-west (on BGS 1:50 000 sheet 218) into the Chipping Norton Limestone Formation; North-west Buckinghamshire; Northamptonshire, south-west of Eydon and Wappenham (on BGS 1:50 000 sheet 202), where the overlying Taynton Limestone Formation passes lithologically north-east into the Wellingborough Member of the Rutland Formation (unpublished BGS data), the Horsehay Formation which can no longer be differentiated passes lithologically into the Stamford Member.
Parent Unit: Great Oolite Group (GOG)
Previous Name(s): White Sands (-976)
Swerford Member (-4110)
Lower Estuarine Series [Inferior Oolite] (-2858)
Swerford Beds (-2255)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Horsehay Quarry, Duns Tew, Oxfordshire. Horton et al. 1987, 57 - 58; Cox, B M, and Sumbler, M G, 2002. 
Reference Section  BGS Charlton Borehole (SP53SW/9). Depth 7.29 to 9.98m. Horton et al., 1987, p.58; Fenton et al., 1994. 
Reference(s):
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
Bradshaw, M J. 1978. A facies analysis of the Bathonian of eastern England. (University of Oxford: Unpublished PhD thesis.) 
Fenton, J P G, Riding, J B, and Wyatt, R J. 1994. Palynostratigraphy of the Middle Jurassic 'White Sands' of central England. Proceedings of the Geologists' Association, Vol. 105, 225-230. 
Horton, A.1977. The age of the Middle Jurassic 'White Sands' of north Oxfordshire. Proceedings of the Geologists' Association, Vol. 88, 147-162. 
Horton, A, Poole, E G, Williams, B J, Illing, V C and Hobson, G D. 1987. Geology of the country around Chipping Norton. Memoir of the British Geological Survey, Sheet 218 (England and Wales). 
Sellwood, B W and Mc Kerrow, W S. 1974. Depositional environments in the lower part of the Great Oolite Group of Oxfordshire and north Gloucestershire. Proceedings of the Geologists' Association, Vol.85, 189-210. 
Sharp, S. 1873. The Oolites of Northamptonshire, Part 2. Quarterly Journal of the Geological Society of London, Vol. 29, 225-302. 
Fenton, J P G, Riding, J B, and Wyatt, R J. 1995. Palynostratigraphy of the Middle Jurassic 'White Sands' of central England: reply to comments by A Horton. Proceedings of the Geologists' Association, Vol. 106, 306-308. 
Sharp, S. 1870. The Oolites of Northamptonshire, Part 1. Quarterly Journal of the Geological Society of London, Vol. 26, 354-391. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E219