The BGS Lexicon of Named Rock Units — Result Details
Highworth Limestone Member
Computer Code: | HWLS | Preferred Map Code: | HwL |
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Status Code: | Full | ||
Age range: | Oxfordian Age (JO) — Oxfordian Age (JO) | ||
Lithological Description: | Bedded shelly ooidal limestone, locally sandy or pisoidal, with thin interbedded calcareous mudstones. Commonly has a basal mudstone chert and sandstone pebble conglomerate, and coralliferous limestones are developed in the Highway area. | ||
Definition of Lower Boundary: | Base is either: (in east) sharp change up from medium- to coarse-grained sand/sandstone of Beckley Sand Member into shelly ooidal limestone with basal conglomerate, or a non-sequence with interbedded yellowish silty and clayey fine quartz sand with sandstone "doggers" and sandy mudstone (Hazelbury Bryan Formation) overlain by shelly ooidal limestone with local conglomerate (Highworth Limestone Member). | ||
Definition of Upper Boundary: | Top is marked by upward change from shelly ooidal limestone of the Highworth Limestone Member into cross-bedded fissile sandy ooidal limestone or calcareous mudstone (Pusey Flags Member), where present, or variably sandy grey to brown mudstone (Highworth Clay Member). Contact might be erosional. | ||
Thickness: | 2 to 3 m in type area, 2.6 m at Lamb and Flag Quarry, thins laterally, 0.3 m at Wooton Bassett. | ||
Geographical Limits: | North Wiltshire to southwest Oxfordshire. Best developed in the area of Highworth; wedges out eastwards near Garford; thins out westwards to zero near Blunsdon. May be thinly represented at Spirt Hill, near Calne, Wiltshire. | ||
Parent Unit: | Kingston Formation (KTON) | ||
Previous Name(s): | Lower Coral Rag
(-973)
Pebble Bed + Pisolite + Lower Trigonia Bed + Upper Trigonia Bed + Urchin Marls (-974) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Reference Section | Lamb and Flag Quarry, Kingston Bagpuize, Oxfordshire. About 0.5m of the upper part of the Member is exposed. Wright in Wright and Cox, 2001. | ||
Reference(s): | |||
Arkell, W J. 1939. Map of the Corallian Beds between Marcham and Faringdon, Berkshire. Proceedings of the Geologists' Association, Vol. 50, 487-509. | |||
Wright, J K, and Cox, B M. 2001. British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian). Geological Conservation Review Series. No. 21. (Peterborough: Joint Nature Conservation Committee/Chapman and Hall.) | |||
Arkell, W J. 1941. Map of the Corallian Beds around Highworth, Wiltshire. Proceedings of the Geologists' Association, Vol. 52, 79-109. | |||
Arkell, W J. 1951. The geology of the Corallian ridge between Wootton Bassett and Lyneham, Wiltshire. Wiltshire Archaeological and Natural History Magazine, Vol. 54, 1-18. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
E253 E252 |