Southern Region Chalk Group Lithostratigraphy: Sussex lithostratigraphy of Mortimore (1986a) - Holywell Beds

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The Holywell Beds (holostratotype section: Beachy Head [TV 588 964]) were named by Mortimore (1986a) after the Holywell cliff sections at Eastbourne. They comprise the interval from the lowest of the Meads Marls (at the top of the Melbourn Rock) to the Malling Street Marls, and are c. 36 m thick in Sussex (Mortimore, 1986a). Hard, nodular, flintless chalk, with fairly regularly developed marl seams is characteristic of the lower and middle Holywell Beds, the higher beds comprising more massive, smoother-textured chalk with more widely spaced marl seams (Mortimore, 1986a). The Meads Marls (arranged into three conspicuous pairs), Holywell Marls and Gun Gardens Marls (in ascending order) are the key marker beds in the succession.

The fauna of the Holywell Beds is dominated by inoceramid bivalves. Inoceramus pictus in the basal part is succeeded upwards by Mytiloides columbianus, M. hattini and M. labiatus. In the middle Holywell Beds the comminuted shell remains of Mytiloides mytiloides are locally abundant and rock-forming. The brachiopod Orbirhynchia cuvieri is characteristic of the interval, and the heteromorph ammonite Sciponoceras is locally common at the base, especially between Meads Marls 2 and 3 (Mortimore, 1986a).

Macrofossil Biozonation: N. juddii Zone (pars), Mytiloides spp. Zone & T. lata Zone

Correlation: see Correlation with other Southern Region Chalk Group classifications

see Correlation with other UK Chalk Group successions

References[edit]

MORTIMORE, R N.1986a. Stratigraphy of the Upper Cretaceous White Chalk of Sussex. Proceedings of the Geologists' Association, Vol. 97(2), 97-139.

See: Melbourn Rock, marl, nodular chalk