The BGS Lexicon of Named Rock Units — Result Details

Portrush Chalk Formation

Computer Code: PRC Preferred Map Code: notEntered
Status Code: Full
Age range: Campanian Age (KC) — Campanian Age (KC)
Lithological Description: Limestone (chalk) with many tabular flint bands and Inoceramus debris in upper part. In the south Antrim area (Southern Uplands High) there are important hardground non-sequences of green-coated chalk pebbles called the South Antrim Hardgrounds (of ?member status).
Definition of Lower Boundary: The lower boundary is conformable, on the Garron Chalk Formation, at a bedding plane beneath a prominent continuous tabular flint.
Definition of Upper Boundary: The upper boundary is taken at a prominent bedding plane above Inoceramus-rich chalk with tabular flint, where it is overlain by chalk of the Ballymagarry Chalk Formation
Thickness: 14.28m in the type section.
Geographical Limits: Found throughout Northern Ireland but is generally absent from much of the East Antrim (Midland Valley) Basin due to pre-Palaeogene basalt erosion. Oversteps onto older strata over the Londonderry Shelf.
Parent Unit: Ulster White Limestone Group (UWLF)
Previous Name(s): Portrush Chalk Member (-2379)
Green Beds (-2748)
Cardiaster Beds (-1770)
Portrush Chalk (-1771)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Sliddery Cove Cliffs east of Portrush. Fletcher (1977). Taken together with the Ballymagarry quarry a complete succession can be viewed. 
Reference Section  Garron Point in East Antrim. 
Type Section  Taken at the south-facing wall of the older and deeper Ballymagarry Quarry, immediately above the main cave that passes beneath the Portrush - Bushmills Road. Fletcher (1977). Taken together with the Sliddery Cove cliffs a complete succession can be viewed. 
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 Unpublished MSc Thesis, Queens University, Belfast. 
Wilson, H E. 1972. The regional geology of Northern Ireland. (Belfast: HMSO for Geological Survey of Northern Ireland.) 113pp. 
Manning, P I, Robbie, J H and Wilson, H E. 1970. Geology of Belfast and the Lagan Valley. Memoir of the Geological Survey of Northern Ireland, Sheet 36 (Northern Ireland). 
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 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable