The BGS Lexicon of Named Rock Units — Result Details

Galboly Chalk Formation

Computer Code: GCK Preferred Map Code: notEntered
Status Code: Full
Age range: Santonian Age (KS) — Santonian Age (KS)
Lithological Description: Chalk, with some flint bands and "incipient flints". Marl partings common towards the base, with some glauconite.
Definition of Lower Boundary: The exact relationship with the underlying Cloghfin Sponge Formation is uncertain (Fletcher, 1977, p.8, paragraph 2). The lower boundary is taken at a well-developed separation plane above which the beds contain no appreciable arenaceous "contamination".
Definition of Upper Boundary: The upper boundary is taken at a prominent bedding plane (an erosion surface in part) immediately above a zone of wavy and disturbed bedding. Overlain by the Cloghastucan Chalk Formation. It is overstepped at basin margins by younger beds of late Cloghastucan or early Creggan Chalk
Thickness: 5.85m at its type section.
Geographical Limits: In Northern Ireland known throughout the North Antrim and East Antrim Basins and parts of the Southern Upland, Highland Border and northern Londonderry Shelf. Absent elsewhere.
Parent Unit: Ulster White Limestone Group (UWLF)
Previous Name(s): Galboly Chalk Member (-1555)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Central Murlough Bay. The full succession is present. 
Reference Section  Milltown. Complete succession from the basal contact with the Senonian Conglomerate up into the top of the Creggan Chalk Formation and could be used as a type section for all of these units. 
Type Section  Roadside "pillar" south of Garron Point [Irish Grid Reference [D 301 245] but this site is noted in Fletcher (1977) as being within an unstable residual block near to the main road. An alternative type section can be "built-up" from foreshore blocks or from the indifferently exposed old quarry at Milltown [D 255 243]. 
Reference(s):
Fletcher, T P. 1967. Correlation of the Cretaceous exposures of east Antrim. Unpublished MSc Thesis, Queens University, Belfast. 
Hopson, P M. 2005. A stratigraphical framework for the Upper Cretaceous Chalk of England and Scotland, with statements on the Chalk of Northern Ireland and the UK Offshore Sector. British Geological Survey Research Report RR/05/01 102pp. ISBN 0 852725175 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable