Chalk Group Lithostratigraphy: Northern Ireland - Ballycastle Chalk Member

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The Ballycastle Chalk Member (stratotype west of Ballycastle Pier [D 120 415]), 13.72 m thick at the type locality (Fletcher, 1977), comprises rather undistinguished flinty chalk, like the underlying Port Calliagh Chalk Member. The member is delimited by a prominent bedding plane at the base, and the top is the Tertiary erosion surface beneath the overlying basalts. The member contains locally developed tabular flints, and carious flints near the top of the succession, but the latter are probably a product of Tertiary weathering (Fletcher, 1977). The fauna of the higher part of the Ballycastle Chalk is dominated by the belemnites Belemnella occidentalis and B. lanceolata, and suggests a correlation with the Trimmingham Sponge Beds Member and Little Marl Point Member of the East Anglian Chalk Group succession (Wood, 1967).

Macrofossil Biozonation: B. lanceolata Zone s.l.& B. occidentalis Zone

Correlation: see Correlation with other UK Chalk Group successions

References[edit]

FLETCHER, T P. 1977. Lithostratigraphy of the Chalk (Ulster White Limestone Formation) in Northern Ireland. Report of the Institute of Geological Sciences, No. 77/24.

WOOD, C J. 1967. Some new observations on the Maestrichtian Stage in the British Isles. Bulletin of the Geological Survey of Great Britain, Vol. 27, 271-288.

See: Trimmingham Sponge Beds Member, Little Marl Point Member