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

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Name

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

Type section

Port Calliagh [D 112 420] inlet west of Castle Point near Ballycastle, north Antrim and to the east under Castle Point.

Primary Reference Section

Ballymagarry Quarry and around Ballycastle Harbour in the North Antrim Basin, in three quarries on the western Londonderry Shelf region, at Whiterock in Belfast and in Small and Hayes Quarry north-east of Lurgan.

Formal subdivision

None but informally divided into units A to F from the base.

Lithology

Limestone (chalk) with numerous flint bands displaying large, tabular and complex habit.

Definition of upper boundary

Conformable at a prominent weathered-out bedding plane at the top of ‘Bed’ F with the Ballycastle Chalk Formation,

Definition of lower boundary

Conformable on the Tanderagee Chalk Formation at the lowest ‘separation plane’ immediately beneath the ‘belt of complex flints’ seen in the Ballycastle section.

Thickness

12.40m at the type-site.

Distribution

Outcrops in the Southern Uplands area (in isolated areas), 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

Port Calliagh Chalk Member.

Forms the lower part of the Ballycastle White Limestone (Wood, 1967).

Parent

Ulster White Limestone Group.

Age and biostratigraphy

Upper Cretaceous, Maastrichtian. Belemnella lanceolata Zone.

References

Fletcher (1967, 1977).