| 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 [Obsolete Name and Code: Use GCK]
(-1555)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| 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 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. |
| 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 Unpublished MSc Thesis, Queens University, Belfast.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 |
