The BGS Lexicon of Named Rock Units — Result Details

Cloghfin Sponge Formation

Computer Code: CSP Preferred Map Code: notEntered
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): Cloughfin Sponge Bed Member [Obsolete Name and Code: Use CSP] (-3337)
Spongiarian Zone [Obsolete Name and Code: Use CSP] (-4573)
Sponge Bed [Obsolete Name and Code: Use CSP] (-172)
Alternative Name(s): none recorded or not applicable
Stratotypes:
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 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(s):
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 Unpublished MSc Thesis, Queens University, Belfast.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. 
Hancock, J M. 1961. The Cretaceous System in Northern Ireland. Quarterly Journal of the Geological Society of London, Vol. 117, 11-36. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable