The Hibernian Greensands Group is a late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

lithostratigraphic Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general, strata are primarily igneou ...

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

(a sequence of rock strata) in

Northern Ireland Northern Ireland ( ga, Tuaisceart Éireann ; sco, label= Ulster-Scots, Norlin Airlann) is a part of the United Kingdom, situated in the north-east of the island of Ireland, that is variously described as a country, province or region. Nort ...

. It is Cenomanian to

Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. ...

in age. The name is derived from the characteristically coloured marls and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s which occur beneath the chalk particularly along the Antrim coast. The strata are exposed on or near to both the northern and eastern coasts of Antrim and also between

Portrush Portrush () is a small seaside resort town on the north coast of County Antrim, Northern Ireland. It neighbours the resort of Portstewart. The main part of the old town, including the railway station as well as most hotels, restaurants and bars, ...

and Dungiven within County Londonderry. Further outcrops occur between

Belfast Belfast ( , ; from ga, Béal Feirste , meaning 'mouth of the sand-bank ford') is the capital and largest city of Northern Ireland, standing on the banks of the River Lagan on the east coast. It is the 12th-largest city in the United Kingdom ...

and

Lurgan Lurgan () is a town in County Armagh, Northern Ireland, near the southern shore of Lough Neagh. Lurgan is about south-west of Belfast and is linked to the city by both the M1 motorway and the Belfast–Dublin railway line. It had a population ...

and between Dungannon and

Magherafelt Magherafelt (, �mˠaxəɾʲəˈfʲiːlt̪ˠə is a small town and civil parish in County Londonderry, Northern Ireland. It had a population of 8,805 at the 2011 Census. It is the biggest town in the south of the county and is the social, econo ...

. It unconformably overlies a variety of units from the Metamorphic Precambrian Southern Highland Group to the Lower Jurassic

Lias Lias may refer to: Geology * Lias Formation, a geologic formation in France *Lias Group, a lithostratigraphic unit in western Europe * Early Jurassic, an epoch People * Godfrey Lias, British author * Mohd Shamsudin Lias (born 1953), Malaysian ...

. The current names replace an earlier situation where the present group was considered to be a formation and each of the present formations was considered a 'member'. Several other stratigraphic naming schemes were in use during the nineteenth century and much of the twentieth century. Various units were earlier referred to as glauconitic or chloritic marls.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 (downloaded from www.bgs.ac.uk) This group and the overlying

Ulster White Limestone Group The Ulster White Limestone Group is a late Cretaceous lithostratigraphic group (a sequence of rock strata) in Northern Ireland. The name is derived from the characteristic chalk rock which occurs particularly along the Antrim coast. The strat ...

are the stratigraphical equivalent of the Chalk Group of southern and eastern England.

Stratigraphy

* Kilcoan Sands Formation *Collinwell Sands Formation *Island Magee Siltstones Formation *Belfast Marls Formation There are

unconformities An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

(non-sequences) above and below the Collinwell Sands Formation.

References

{{Geology of Northern Ireland Geologic groups of Europe Geological groups of the United Kingdom Upper Cretaceous Series of Europe Geology of Ireland Geology of Northern Ireland