The BGS Lexicon of Named Rock Units — Result Details

Harford Member

Computer Code: HFD Preferred Map Code: Hf
Status Code: Full
Age range: Aalenian Age (JA) — Aalenian Age (JA)
Lithological Description: Interbedded yellow silty fine-grained sand, cemented in parts ('Harford Sands'), grey and brown mudstone, shelly and sandy in parts ('Snowshill Clay' and 'Naunton Clay') and variably sandy and ooidal limestone ('Tilestone'). The succession is characterised by rapid lateral facies transitions and a mix of fully marine and quasi-non-marine facies.
Definition of Lower Boundary: Upward change or passage from peloidal and ooidal packstones and grainstones (Scottsquar Member) to lithologies as described in Lithological Description. Locally a non-sequence marked by a hardground (Buckman, J, 1901; Cave, R and Penn, I E, 1972).
Definition of Upper Boundary: Sharp contact, generally a hardground, overlain by Aston Limestone Formation, or hardground overlain by Salperton Limestone Formation.
Thickness: Up to 14m. Type section (Harford Cutting); 3.05m+ (Parsons, C F, 1976). Thickens northward.
Geographical Limits: Cotswold Hills, Gloucestershire: north of Chedworth, west of Bourton-on-the-Water and Moreton-in-Marsh (Barron, A J M, et al, 1997, fig.4).
Parent Unit: Birdlip Limestone Formation (BLPL)
Previous Name(s): Snowshill Clay [Obsolete Name And Code: Use HFD] (SHC)
Stanway Hill Formation (-313)
Tilestone (-314)
Naunton Clay (-956)
Grouping Of Harford Sands (-3464)
Harford Sands Member (-3465)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Jackdaw Quarry SSSI, Stanway, Gloucestershire. Parsons, C F, 1976; Mudge, D C, 1978a; 1978b; Cox, B M, and Sumbler, M G. 2002. For further reference sections see Barron, A J M, et al, 1997. 
Type Area  North Cotswolds, Gloucestershire. 
Type Section  Harford railway cutting SSSI, Gloucestershire. Buckman, J, 1887, section 4; Woodward, H B, 1894, fig.43, cutting Q; Richardson, L, 1929, p.79; Beds 1 to 2b of Parsons, C F, 1976; Barron, A J M, 1999; Cox, B M, and Sumbler, M G. 2002. 
Reference(s):
Barron, A J M, Sumbler, M G and Morigi, A N, 1997. A revised lithostratigraphy for the Inferior Oolite Group (Middle Jurassic) of the Cotswolds, England. Proceedings of the Geologists' Association, Vol.108, 269-285. 
Buckman, S S, 1887. The Inferior ooilte between Andoversford and Bourton-on-the-Water. Proceedings of the Cotteswold Naturalists' Field Club, Vol.9, 108-135. 
Parsons, C F, 1976. Ammonite evidence for dating some Inferior Oolite sections in the North Cotswolds. Proceedings of the Geologists' Association, 87, 45-63. 
Parsons, C F, 1980. Aspects of the statigraphy and ammonite faunas of the Aaenian-Bajocian stages in Great Britain. Unpublished PhD thesis, University of Keele. 
Buckman, S S, 1897. Deposits of the Bajocian age in the northern Cotswolds: the Cleeve Hill Plateau. Quarterly Journal of the Geological Society of London, Vol.53, 607-629. 
Buckman, S S, 1901. Bajocian and contiguous deposits in the north Cotswolds: the main hill-mass. Quarterly Journal of the Geological Society of London, Vol.57, 126-155. 
Cave, R and Penn, I E, 1972. On the classification of the Inferior Oolite of the Cotswolds. Bulletin of the Geological Survey of Great Britain, No.38, 59-65. 
Mudge, D C, 1978. Stratigraphy and sedimentation of the Lower Inferior Oolite of the Cotswolds. Journal of the Geological Society of London, Vol.135, 611-627. 
Woodward, H B, 1894. The Jurassic Rocks of Britain, Vol.4. The Lower Oolitic Rocks of England (Yorkshire excepted). Memoir of the Geological Survey of the United Kingdom. 
Barron, A J M, 1999. Geology of the Naunton area. British Geological Survey Technical Report WA/98/27. 
Richardson, L. 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217 (England and Wales). 
Cox, B M and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E235 E217