Chalk Group Lithostratigraphy: Northern Ireland - Boheeshane Chalk Member

The Boheeshane Chalk Member (stratotype: Boheeshane Bay [D 268 699]), with a maximum thickness of 24.19 m at the type locality, comprises finer-grained, flinty chalk than the underlying units, mostly due to the absence of comminuted inoceramid shell (Fletcher, 1977). Fletcher (1977), and Wilson & Manning (1978) recognised various subdivisions of the Boheeshane Member, but this seems to be mostly governed by faunal criteria, the type section of the member appearing to comprise rather uniformly flinty chalk, although large flints are commoner in the upper part. The Boheeshane Chalk is delimited by the Bendoo Pebble Bed at the base, and an erosion surface (below the Larry Bane Member) at the top.

The member contains several fossil-rich horizons (the basis for the over-elaborate subdivision of this member), including acmes of brachiopods, belemnites and echinoids. One conspicuous flint near the top of the member, named the Whitehead Flint Band, marks the biostratigraphically significant upper range of the belemnite Gonioteuthis.

Macrofossil Biozonation: G. quadrata Zone & B. mucronata Zone (lower part)

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.