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

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The Old Nore Beds, locally c. 23 m thick in Sussex, are marked by the Brighton Marl at the base and the Old Nore Marl at the top (Mortimore, 1986a). They comprise mostly soft, flinty chalk with conspicuous marl seams, often occurring as pairs, 0.3 to 0.6 m apart (Mortimore, 1986a). Concentrations of sponges and local horizons of abundant calcareous nannoplankton produce beds of harder chalk, and tubular, finger and large nodular horn flints also occur (Mortimore, 1986a). Key named marls (in ascending order) are the Brighton Marl, Kemptown Marl, Friar's Bay Marls, Ovingdean Marl, Black Rock Marl, Saltdean Marl, Rottingdean Paired Marls, and Roedean Triple Marls (Mortimore, 1986a). The main flints (again in ascending order) are the Kemptown Flint, Sheepcote Valley Flint and Friar's Bay Flint , all found in the lower part of the succession (Mortimore, 1986a), although an un-named conspicuous flint occurs at the top of the succession below the Old Nore Marl (Young & Lake, 1988, Fig. 16).

The fauna of the lower part of the succession, is dominated by the crinoids Marsupites testudinarius and Uintacrinus anglicus, the former having several acmes, and showing morphological changes that are of value for correlation (Mortimore, 1986a). A rich oyster fauna, characterised in particular by Pseudoperna boucheroni, also occurs through this interval (Young & Lake, 1988). Acmes of the echinoid Echinocorys elevata in the lower part of the succession, are overlain by bands with common E. tectiformis, E. depressula and E. truncata (Young & Lake, 1988).

Macrofossil Biozonation: middle & upper M. testudinarius Zone, U. anglicus Zone & lower O. pilula Zone

Correlation: see Correlation with other Southern Region Chalk Group classifications

see Correlation with other UK Chalk Group successions

References[edit]

LAKE, R D, YOUNG, B, WOOD, C J & MORTIMORE, R N. 1987. Geology of the country around Lewes. Memoir of the British Geological Survey.

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

See: flint, marl