Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Hibernian Greensands Group: Collinwell Sands Formation
Name
The Collinwell Sands Member was first used in Griffith and Wilson (1982). The term is upgraded to formation status herein.
Type section
The formation is best developed southwest of Belfast and was described from a type area around Collin Glen [J 269 702] in terms of the old Glauconitic Sands. This site is reported in Manning, Robbie and Wilson (1970) to be obscured by landslips. The member was named after the quarry at Collinwell [J 269 701] nearby.
Primary Reference Section
Kilcoan Old Quarry [J 461 985] and numerous localities on the Larne, Antrim, Carrickfergus and Belfast sheet areas (see Griffith and Wilson (1982), Page 48, Figure 16A).
Formal subdivisions
None
Lithology
Pale green to grey coarse-grained unconsolidated sands with some glauconite. Becomes whitish and poorly glauconitic in the Carrickfergus district.
Definition of upper boundary
Unconformable at an erosion surface with younger Kilcoan Sands Formation beneath the so-called Turonian non-sequence within the Hibernian Greensands Group; and beneath the erosion surface at the base of the Ulster White Limestone Group.
Definition of lower boundary
Disconformable at an erosional surface upon the Island Magee Siltstones Formation.
Thickness
Maximum of 2.4m at Rungill Burn in the Carrickfergus district.
Distribution
Fully developed in the area southwest of Belfast within the East Antrim Basin and Southern Uplands area. Elsewhere in Northern Ireland the formation may be represented in the condensed successions of the undivided Hibernian Greensands Group.
Previous names
Part of the Glauconitic Sands of Tate (1865); part of the Chloritic Sands and Sandstones of Hume (1897); lower part (‘Basement Sands’) of the Upper Glauconitic Beds of Hancock (1961); part of the Lower Hibernian Greensands of Reid (1971); the Quartzose Sand (part of the Cenomanian/Turonian Greensands) of Manning, Robbie and Wilson (1970).
Collinwell Sands Member in BGS publications.
Parent
Hibernian Greensands Group.
Age and biostratigraphy
Upper Cretaceous, Uppermost Cenomanian and Turonian. Rhynchostreon suborbiculatum Zone.
References
Fletcher (1967); Griffith and Wilson (1982).