| Computer Code: |
CHAR |
Preferred Map Code: |
ChL |
| Status Code: |
Full |
| Age range: |
Bathonian Age (JN)
— Bathonian Age (JN) |
| Lithological Description: |
Mainly lime-muddy, shelly, shell-detrital limestones and some ooid-grainstones and ooidal limestones (limestone 60-80% of the formation); subordinate shelly, shell-detrital calcareous mudstone with subordinate silicate mudstone; entire fossils abundant. |
| Definition of Lower Boundary: |
Well-defined by the sharp change up into limestone beds from dark bluish grey mudstone of the Sharp's Hill Formation. |
| Definition of Upper Boundary: |
Defined throughout by base of the undifferentiated Taynton Limestone Formation, which comprises mainly non-muddy, commonly cross-bedded, shell-detrital ooid-grainstones and ooidal limestones in which entire fossils are rare. |
| Thickness: |
Generally 3 to 5m. 3-3.6m at the type section. 4.2-4.8m in boreholes near Stonesfield, Oxon, about 3km south-east of type section. 4.83m in Stonesfield Borehole No 3 (reference section). |
| Geographical Limits: |
North Oxfordshire Cotswolds east of 'Vale of Moreton Axis': limit based on classification of cored boreholes and gamma-ray log characterisation. Extends in the subcrop 10km east of Charlbury. Wyatt (2011) also infers its extension south-east into the Weald Basin. North-eastern limit poorly defined but may undergo lateral passage into the Rutland Formation some 10km north-east of Chipping Norton. |
| Parent Unit: |
Taynton Limestone Formation (TY)
|
| Previous Name(s): |
Part Of Sharp's Hill Formation
(-5117)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Town Quarry, Charlbury, Oxfordshire (1.6km east-north-east of Charlbury Church). Exposed the entire member 3 to 3.6m thick, overlain by the Taynton Limestone Formation and underlain by the Sharp’s Hill Formation. Now thought to be an SSSI. NGR above is as in Wyatt citation, however, there would seem to be a preserved face (2013) [SP 3704 2015] which is likely to expose the upper part of the section described. See Wyatt, pp. 215-218 in Cox and Sumbler (2002), see also Horton et al. (1987, pp. 78-79) and BGS photographs P212722 and P212723. |
| Reference Section |
BGS Stonesfield Borehole No 3 (SP31NE15). Between 20.47 and 25.30m depth. Cored borehole sequence. Almost complete half-core stored at BGS Keyworth. Boneham and Wyatt (1993) |
| Reference(s): |
| 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. |
| 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). |
| Cox, B M, and Sumbler, M G. 2002. British Middle Jurassic Stratigraphy. Geological Conservation Review Series No.26. [Peterborough: Joint Nature Conservation Committee.] |
| Richardson, L. 1929. The Country around Moreton in Marsh. Memoir of the Geological Survey of Great Britain, Sheet 217 (England and Wales). |
| Wyatt, R J. 2000. Correlation of the Bathonian (Middle Jurassic) succession in the Minchinhampton-Burford district. Proceedings of the Geologists' Association, Vol. 111, 187-189. |
| Wyatt, R J. 2004. Interpretation of Stowell Park Borehole, Gloucestershire and definition of the Middle Jurassic Througham Formation. An update on Wyatt et al. Proceedings, Vol. 111, 2000, pp. 187-189. Proceedings of the Geologists' Association, Vol. 115, 187-188. |
| Wyatt, R J. 2011. A gamma-ray correlation of boreholes and oil wells in the Bathonian Stage succession (Middle Jurassic) of the Wealden Shelf subcrop. British Geological Survey Open Report, OR/11/048. |
| Boneham, B F W, and Wyatt, R J. 1993. Stratigraphical position of the Middle Jurassic (Bathonian) Stonesfield Slate. Proceedings of the Geologists' Association, Vol. 104, Pt. 2, 123-136. |
| Wyatt, R J. 1996. A correlation of the Bathonian (Middle Jurassic) succession between Bath and Burford, and its relation to that near Oxford. Proceedings of the Geologists' Association, Vol. 107, 299-322. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
