Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Ulster White Limestone Group: Post-Larry Bane Chalk Subgroup: Ballymagarry Chalk Formation: Difference between revisions
No edit summary |
m Changed protection level for "Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Ulster White Limestone Group: Post-Larry Bane Chalk Subgroup: Ballymagarry Chalk Formation" ([Edit=Allow only administrators] (indefinite) [Move=Allow onl |
| (One intermediate revision by the same user not shown) | |
(No difference)
| |
Latest revision as of 13:14, 11 June 2014
Name
The Ballymagarry Chalk Member was first proposed in Fletcher (1977) and adopted in BGS publications subsequently. It is regarded as a formation herein.
Type section
Ballymagarry Quarry [C 889 407].
Primary Reference Section
The western side of Port More [D 073 439] and Downhill in north Derry.
Found throughout the Londonderry Shelf, North Antrim Basin and Southern Uplands High. Absent from the Midland Valley (East Antrim) Basin and Highland Border High.
Formal subdivisions
None but informally divided into units A to C from the base.
Lithology
Limestone (chalk) with extremely large flat lying and near-continuous flint bands. Divided into three ‘Beds’ (A to C) separated by well-marked bedding planes.
Definition of upper boundary
Marked by the base of the prominent continuous flint band termed the Long Gilbert Flint Band within the Tanderagee Chalk Formation.
Definition of lower boundary
Conformably overlies the Portrush Chalk Formation at a level of a well-marked bedding plane immediately below the inception of large flat lying and near continuous flint nodules.
Thickness
10.95m at its type-site.
Distribution
Absent from the Highland Border High and East Antrim Basin presumably by pre-Palaeogene erosion.
Previous names
Ballymagarry Chalk Member.
Parent
Ulster White Limestone Group.
Age and biostratigraphy
Upper Cretaceous, Campanian. Belemnitella mucronata Zone sensu lato.
References
Fletcher (1977).