Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Ulster White Limestone Group: Post-Larry Bane Chalk Subgroup: Tanderagee Chalk Formation

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Name

The Tanderagee Chalk Member was first proposed in Fletcher (1977) and adopted in BGS publications subsequently. It is regarded as a formation herein.

Type section

Long Gilbert Quarry, Ballymagarry [C 889 407], south wall of western part of quarry.

Primary Reference Section

Numerous in the North Antrim Basin, the southern Londonderry Shelf and in the Southern Uplands. It is seen in sections between Magheralin and Trummery, Groganstown and the ‘Hairpin Bend’ region of Ballysillan, Ballycastle to Ballintoy, Portbraddan to Downhill and between Carmean and Stewartstown.

Formal subdivision

Includes the Long Gilbert Flint Band (of bed status) and informally divided into units A to E from the base.

Lithology

Limestone (chalk) with flint bands. Divided into five ‘Beds’ (A to E). Abundant belemnites in lower ‘Bed’ A and by an acme of crinoid debris in ‘Bed’ C. Elsewhere asteroid and crinoid debris common.

Definition of lower boundary

Conformable, on the Ballymagarry Chalk Formation, at a bedding plane immediately below the thick continuous tabulate Long Gilbert Flint Band where this exists. Or at the same bedding plane marking the faunal change from the Ballymagarry Chalk Formation fauna.

Definition of upper boundary

Conformable, with the overlying Port Calliagh Chalk Formation, at a bedding plane below a ‘belt of complex flints’.

Thickness

7.63m at type-site.

Distribution

Outcrops in the Southern Uplands area, the North Antrim Basin and in the southern part of the Londonderry Shelf. Absent in the East Antrim Basin, the Highland Border High and northern Londonderry shelf due to pre-Palaeogene erosion.

Previous names

Tanderagee Chalk Member.

Parent

Ulster White Limestone Group.

Age and biostratigraphy

Upper Cretaceous, Maastrichtian. Belemnella lanceolata Zone?

References

Fletcher (1977).