The BGS Lexicon of Named Rock Units — Result Details
Cloghfin Sponge Formation
Computer Code: | CSP | Preferred Map Code: | notEntered |
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Status Code: | Full | ||
Age range: | Santonian Age (KS) — Santonian Age (KS) | ||
Lithological Description: | Chalk and chalk conglomerate/breccia, glauconitic, with conspicuous hexactinellid sponge pseudomorphs. Three separate beds recognised (A, B, C) each with characteristic shape-variants of the irregular echinoid Echinocorys. | ||
Definition of Lower Boundary: | Everywhere the base rests unconformably upon eroded Hibernian Greensand Group successions. In the most complete Hibernian Greensands Formation sequences (Kilcoan [J461 985]) the base of the Clochfin Sponge Formation is 4.27m above the conspicuous "Inoceramus Bands". | ||
Definition of Upper Boundary: | The exact relationship with the overlying Galboly Chalk Formation is not certain (Fletcher, 1978 p.8 para. 2). It is taken at a well-developed separation plane below which the beds contain arenaceous "contamination". | ||
Thickness: | As defined in the type-site the beds are 1.4m thick. | ||
Geographical Limits: | The Formation is limited to the East Antrim Basin Northern Ireland. Restricted to the southeast Antrim region between Little Deer Park near Glenarm and Castle Dobbs. | ||
Parent Unit: | Ulster White Limestone Group (UWLF) | ||
Previous Name(s): | Spongiarian Zone [Obsolete Name and Code: Use CSP]
(-4573)
Sponge Bed [Obsolete Name and Code: Use CSP] (-172) Cloughfin Sponge Bed Member [Obsolete Name and Code: Use CSP] (-3337) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Reference Section | Near Kilcoan. Where the formation rests on the "most complete greensand sequence" (Fletcher, 1977). | ||
Type Section | On the shore near Whitehead and Hillsport, Island Magee; Fletcher (1967, 1977) . Three separate beds are recognised within 1.47m of strata. | ||
Reference Section | Cloghfin Port. The section, "on the south end of Islandmagee, has long been associated with these sponge beds" (Fletcher, 1967) and from which the formation takes its name. | ||
Reference(s): | |||
Hancock, J M. 1961. The Cretaceous System in Northern Ireland. Quarterly Journal of the Geological Society of London, Vol. 117, 11-36. | |||
Fletcher, T P. 1977. Lithostratigraphy of the Chalk (Ulster White Limestone Formation) in Northern Ireland. Report of the Institute of Geological Sciences, No. 77/24. | |||
Fletcher, T P. 1967. Correlation of the Cretaceous exposures of east Antrim. Unpublished MSc Thesis, Queens University, Belfast. | |||
Hume, W F. 1897. The Cretaceous strata of County Antrim. Quarterly Journal of the Geological Society of London, Vol.53, 540-606. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
none recorded or not applicable |