The BGS Lexicon of Named Rock Units — Result Details

Chilmark Member

Computer Code: CHK Preferred Map Code: Chk
Status Code: Full
Age range: Tithonian Age (JI) — Tithonian Age (JI)
Lithological Description: Fine-grained oolitic limestone.
Definition of Lower Boundary: Incoming of significant ooliths above sequence of micrites of the Wockley Member.
Definition of Upper Boundary: Base of "Dirt Bed" at base of Purbeck Formation.
Thickness: 0-6m.
Geographical Limits: On north side of river Nadder between Fonthill Bishop and Chilmark; south of River Nadder between Wockley [ST 9555 2870] and Chicksgrove [ST 964 296] quarries.
Parent Unit: Portland Stone Formation (POST)
Previous Name(s): Upper Building Stones [Obsolete Name and Code: Use CHK] (-1427)
Chilmark Oolite Member [Obsolete Name and Code: Use CHK] (-2082)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Upper Quarry (Teffont Evias Parish), RAF Chilmark 
Reference(s):
Hudleston W H, 1883 (for 1881). On the geology of the Vale of Wardour. Proceedings of the Geologists' Association. Vol.7, 161-185. 
Wimbledon, W A and Cope, J C W. 1978. The ammonite faunas of the English Portland Beds and the zones of the Portlandian Stage. Journal of the Geological Society of London, Vol.135, 183-190. 
Wimbledon, W A. 1976. The Portland Beds (Upper Jurassic) of Wiltshire. Wiltshire Archaeological and Natural History Magazine, Natural History, Vol.71, 3-11. 
Woodward, H B. 1895. the Jurassic Rocks of Britain. The Middle and Upper Oolitic rocks of England (Yorkshire excepted). Vol.5. Memoir or the Geological Survey of the United Kingdom. 
Blake, J F. 1880. On the Portland Rocks of England. Quarterly Journal of the Geological Society of London, Vol. 36, 189-236. 
Wimbledon, W A. 1980. Portlandian correlation chart. 85-93 in Cope, J C W (Editor), A correlation of the Jurassic rocks of the British Isles. Part Two: Middle and Upper Jurassic. Geological Society of London Special Report, No.15. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E297