Category:Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group
Name
The name was first proposed by Tate (1865) as Hibernian Greensand. Hancock (1961) used the term Hibernian Greensands. Hibernian Greensands Formation was adopted in BGS publications and in Fletcher (1967). Elevated to Group status herein.
Type section
Numerous exposures of the constituent formations (see formal subdivisions below for reference to those divisions) in the Midland (East Antrim) Basin and Southern Uplands district.
Primary Reference Section
Cloghfin Port [J 483 938], Magheramorne borehole [J 433 975 and area, Collin Glen [J 269 702] district southwest of Belfast, Kilcoan Old Quarry [J 461 985] on Island Magee.
Formal subdivisions
Divided into four members as in BGS memoir (e.g. Griffith and Wilson, 1982). It is proposed herein that the group be divided at the formation level in ascending order, the Belfast Marls Formation, the Island Magee Siltstones Formation, the Collinwell Sands Formation and the Kilcoan Sands Formation.
Lithology
Glauconitic ‘marls’, argillaceous siltstones and calcareous sandstones, and quartzose sands. Sequence divided into four formations noted above.
Definition of upper boundary
Unconformable at a major regional erosional break. Overlain by various members of the Ulster White Limestone Group.
Definition of lower boundary
Unconformable on a variety of older formations at a major regional erosinal break at the base of the Belfast Marls Member.
Thickness
About 21m to 22m in the Carrickfergus, Larne, Antrim and Belfast sheet areas.
Distribution
Throughout Northern Ireland. As a thin basal Cretaceous unit over structural highs and in the North Antrim Basin, where the group is undivided. Fullest development in the Midland Valley (East Antrim Basin) and the Southern Uplands as defined in Fletcher (1977) where group is divided.
Previous names
‘Mulatto’ a collective term for the greensands, conglomerates and marls beneath the White Limestone (Whitehurst, 1786); the ‘Greensands’ of Portlock (1843); Hibernian Greensand of Tate (1865); part of Hibernian Greensands as defined by Hancock (1961); the Upper and Lower Hibernian Greensands of Reid (1971). Hibernian Greensand Formation in BGS publications and Fletcher (1967).
Parent
None
Age and biostratigraphy
Upper Cretaceous, Cenomanian to Santonian. Various basal Upper Cretaceous zones up to Micraster coranguinum Zone.
References
Fletcher (1967, 1977); Griffith and Wilson (1982).
The following entries, in stratigraphical order from the base, for the formations of the Hibernian Greensands Group form part of the Lexicon derived from its precursor Dic_Strat (as code only entries). They are not shown individually upon maps of Northern Ireland but are described in various publications from the Province (see note above concerning the adoption of Hibernian Greensand Group as the formal notation for this succession of beds thus raising the rank of each of the following from member status).
Pages in category "Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group"
The following 4 pages are in this category, out of 4 total.
- Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group: Belfast Marls Formation
- Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group: Island Magee Siltstones Formation
- Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group: Collinwell Sands Formation
- Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group: Kilcoan Sands Formation