Chalk Group Lithostratigraphy: Northern Ireland - Tanderagee Chalk Member

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The Tanderagee Chalk Member (stratotype: Ballymagarry Quarry [C 889 407]), 7.63 m thick at the type locality, comprises rather undistinguished flinty chalk, and is recognised principally on faunal criteria (Fletcher, 1977; Wilson & Manning, 1978). The member is delimited locally by the tabular Long Gilbert Flint at the base, and by a bedding plane, c. 0.3 m below a complex tabular flint with downward prolongations (informally named the 'drip flint'), at the top (Wilson & Manning, 1978). At many localities however, the Long Gilbert Flint is absent, and the basal boundary is a bedding plane (Fletcher, 1977). The fauna that distinguishes this member comprises the crinoid Austinocrinus bicoronatus, asteroid debris, the echinoid Echinocorys belgica and the belemnite Belemnitella ex gr. posterior, indicative of the Maastrichtian, and broadly coeval with the lower part of the Sidestrand Chalk Member of the East Anglian Chalk Group succession (Wilson & Manning, 1978). The locally developed Long Gilbert Flint is taken as the Campanian / Maastrichtian boundary marker (Wilson & Manning, 1978).

Macrofossil Biozonation: B. lanceolata 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.

WILSON, H E & MANNING, P I. Geology of the Causeway Coast, Vol. 2. Memoir of the British Geological Survey of Northern Ireland.

See: Sidestrand Chalk Member