The BGS Lexicon of Named Rock Units — Result Details

Island Magee Siltstone Formation

Computer Code: ISMS Preferred Map Code: notEntered
Status Code: Full
Age range: Cenomanian Age (KE) — Cenomanian Age (KE)
Lithological Description: Hard and soft grey siltstones and marls (calcareous siltstones) that weather to a pale yellow colour.
Definition of Lower Boundary: The lower boundary is conformable with the underlying Belfast Marls Formation, with the boundary arbitrarily taken at the base of the first upwardly occurring hard calcareous siltstone above the transitional top of the preceding formation.
Definition of Upper Boundary: The upper boundary is disconformable with the Collinwell Sands Formation and unconformable with the Kilcoan Sands Formation beneath the so-called Turonian non-sequence of the Hibernian Greensands Group.
Thickness: A maximum of 8.0m in the Magheramorne area and a minimum of 0.67m over the Knockagh Axis north of Belfast.
Geographical Limits: East Antrim Basin and the Southern Uplands area of Northern Ireland.
Parent Unit: Hibernian Greensands Group (HBG)
Previous Name(s): Grey Marls And Yellow Sandstones With Chert (-1616)
Yellow Sandstones (-3489)
Island Magee Silts Member (-4721)
Yellow Sandstones And Grey Marls (-4722)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Magheramorne area (Larne area). The formation is best developed in this area. 
Type Section  Cloghfin (Carrickfergus area), Succession exposed in foreshore reefs. 
Type Section  Collin Glen (Belfast area), Succession has a more diverse fauna in unevenly bedded fine-grained calcareous sandstone with irregular doggers. 
Reference Section  Kilcoan Old Quarry. 
Reference(s):
Griffith, A E and Wilson, H E. 1982. Geology of the country around Carrickfergus and Bangor. Memoir of the Geological Survey of Northern Ireland. Sheet 29 (Northern Ireland). 
Hume, W F. 1897. The Cretaceous strata of County Antrim. Quarterly Journal of the Geological Society of London, Vol.53, 540-606. 
Reid, R E H. 1971. The Cretaceous rocks of north-eastern Ireland. Irish Naturalists' Journal, Vol.17, 105-129. 
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). 
Hancock, J M. 1961. The Cretaceous System in Northern Ireland. Quarterly Journal of the Geological Society of London, Vol. 117, 11-36. 
Tate, R. 1865. On the correlation of the Cretaceous formations of north-east Ireland. Quarterly Journal of the Geological Society of London, Vol. 21, 15-44. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable