Northern Ireland Chalk nomenclature (Ulster Cretaceous Province) - Ulster White Limestone Group: Post-Larry Bane Chalk Subgroup: Portrush Chalk Formation: Difference between revisions
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Name | =====Name===== | ||
The Portrush Chalk Member was first proposed in Fletcher (1967, 1977) and adopted in BGS publications subsequently. It is regarded as a formation herein. | The Portrush Chalk Member was first proposed in Fletcher (1967, 1977) and adopted in BGS publications subsequently. It is regarded as a formation herein. | ||
=====Type section===== | |||
Type section | |||
Taken at the south-facing wall of the older and deeper Ballymagarry Quarry [C 890 408], i.e. immediately above the main cave which passes beneath the Portrush – Bushmills Road. | Taken at the south-facing wall of the older and deeper Ballymagarry Quarry [C 890 408], i.e. immediately above the main cave which passes beneath the Portrush – Bushmills Road. | ||
Sliddery Cove Cliffs [C 890 410] east of Portrush | Sliddery Cove Cliffs [C 890 410] east of Portrush | ||
=====Primary Reference Section===== | |||
Primary Reference Section | |||
Garron Point [D 301 2390 in East Antrim Basin. | Garron Point [D 301 2390 in East Antrim Basin. | ||
=====Formal subdivision===== | |||
Formal subdivision | |||
Includes the South Antrim Hardgrounds (of Member status) and informally divided into units A to D from the base. | Includes the South Antrim Hardgrounds (of Member status) and informally divided into units A to D from the base. | ||
=====Lithology===== | |||
Lithology | |||
Limestone (chalk) with many tabular flint bands and Inoceramus debris in upper part. In the south Antrim area (Southern Uplands High) there are important hardground non-sequences of green-coated chalk pebbles called the South Antrim Hardgrounds (of member? status). | Limestone (chalk) with many tabular flint bands and Inoceramus debris in upper part. In the south Antrim area (Southern Uplands High) there are important hardground non-sequences of green-coated chalk pebbles called the South Antrim Hardgrounds (of member? status). | ||
=====Definition of upper boundary===== | |||
Definition of upper boundary | |||
At a prominent bedding plane above Inoceramus-rich chalk with tabular flint. | At a prominent bedding plane above Inoceramus-rich chalk with tabular flint. | ||
=====Definition of lower boundary===== | |||
Definition of lower boundary | |||
Conformable, on the Garron Chalk Formation, at a bedding plane beneath a prominent continuous tabular flint. | Conformable, on the Garron Chalk Formation, at a bedding plane beneath a prominent continuous tabular flint. | ||
=====hickness===== | |||
14.28m in the type section. | 14.28m in the type section. | ||
=====Distribution===== | |||
Distribution | |||
Found consistently throughout the province but is generally absent from much of the East Antrim (Midland Valley) Basin due to pre-Palaeogene basalt erosion. Oversteps onto older strata over the Londonderry Shelf. | Found consistently throughout the province but is generally absent from much of the East Antrim (Midland Valley) Basin due to pre-Palaeogene basalt erosion. Oversteps onto older strata over the Londonderry Shelf. | ||
=====Previous names===== | |||
Previous names | |||
Portrush Chalk of Fletcher (1967) | Portrush Chalk of Fletcher (1967) | ||
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Is equivalent to the Cardiaster Beds described by Wood (in Wilson, 1972). The term ‘Green Beds’ is utilised as a mappable unit in Manning et al. (1970) for the South Antrim Hardgrounds. | Is equivalent to the Cardiaster Beds described by Wood (in Wilson, 1972). The term ‘Green Beds’ is utilised as a mappable unit in Manning et al. (1970) for the South Antrim Hardgrounds. | ||
=====Parent===== | |||
Parent | |||
Ulster White Limestone Group. | Ulster White Limestone Group. | ||
=====Age and biostratigraphy===== | |||
Age and biostratigraphy | |||
Upper Cretaceous, Campanian. Belemnitella mucronata Zone sensu lato. | Upper Cretaceous, Campanian. Belemnitella mucronata Zone sensu lato. | ||
=====References===== | |||
References | |||
Fletcher (1967, 1977). | Fletcher (1967, 1977). | ||
[[category:Northern_Ireland_Chalk_nomenclature_(Ulster_Cretaceous_Province)_-_Ulster_White_Limestone_Group:_Post-Larry_Bane_Chalk_Subgroup | 04]] | [[category:Northern_Ireland_Chalk_nomenclature_(Ulster_Cretaceous_Province)_-_Ulster_White_Limestone_Group:_Post-Larry_Bane_Chalk_Subgroup | 04]] | ||
Latest revision as of 13:13, 11 June 2014
Name
The Portrush Chalk Member was first proposed in Fletcher (1967, 1977) and adopted in BGS publications subsequently. It is regarded as a formation herein.
Type section
Taken at the south-facing wall of the older and deeper Ballymagarry Quarry [C 890 408], i.e. immediately above the main cave which passes beneath the Portrush – Bushmills Road.
Sliddery Cove Cliffs [C 890 410] east of Portrush
Primary Reference Section
Garron Point [D 301 2390 in East Antrim Basin.
Formal subdivision
Includes the South Antrim Hardgrounds (of Member status) and informally divided into units A to D from the base.
Lithology
Limestone (chalk) with many tabular flint bands and Inoceramus debris in upper part. In the south Antrim area (Southern Uplands High) there are important hardground non-sequences of green-coated chalk pebbles called the South Antrim Hardgrounds (of member? status).
Definition of upper boundary
At a prominent bedding plane above Inoceramus-rich chalk with tabular flint.
Definition of lower boundary
Conformable, on the Garron Chalk Formation, at a bedding plane beneath a prominent continuous tabular flint.
hickness
14.28m in the type section.
Distribution
Found consistently throughout the province but is generally absent from much of the East Antrim (Midland Valley) Basin due to pre-Palaeogene basalt erosion. Oversteps onto older strata over the Londonderry Shelf.
Previous names
Portrush Chalk of Fletcher (1967)
Portrush Chalk Member.
Is equivalent to the Cardiaster Beds described by Wood (in Wilson, 1972). The term ‘Green Beds’ is utilised as a mappable unit in Manning et al. (1970) for the South Antrim Hardgrounds.
Parent
Ulster White Limestone Group.
Age and biostratigraphy
Upper Cretaceous, Campanian. Belemnitella mucronata Zone sensu lato.
References
Fletcher (1967, 1977).