Chalk Group Lithostratigraphy: Northern Ireland - Port Calliagh Chalk Member

The Port Calliagh Chalk Member (stratotype: Port Calliagh [D 112 420]), 12.4 m thick at the type locality (Fletcher, 1977), comprises rather undistinguished flinty chalk, and the basis for its recognition as a separate member is presumably faunal, although this is not clear from the published accounts. The member is delineated by bedding planes (Fletcher, 1977), and these are also used as the basis for further (probably over-elaborate) subdivision. A locally occurring complex tabular flint with downward prolongations occurs a short distance above the base of the member (informally named the 'drip flint'), although locally this appears to become a belt of complex nodular flints (Wilson & Manning, 1978). The lower part of the member contains the belemnite Belemnitella, which is replaced upwards by the more characteristically Maastrichtian Belemnella (Fletcher, 1977). The fauna from inferred lateral equivalents of the Port Calliagh Member suggests a correlation with the higher part of the Sidestrand Chalk Member of the East Anglian Chalk Group succession (Wilson & Manning, 1978).

Macrofossil Biozonation: B. lanceolata Zone

Correlation: see Correlation with other UK Chalk Group successions

References

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