Southern Region Chalk Group Lithostratigraphy: Bristow et al. (1997) - Lower Chalk

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Comprises West Melbury Marly Chalk overlain by Zig Zag Chalk, with or without Glauconitic Marl at the base (Bristow et al., 1997). Mostly corresponds with the traditional concept of the Lower Chalk (the top in both cases being marked by the Plenus Marls), except that in some areas (e.g. south-west Wiltshire) strata formerly regarded as Glauconitic Marl are reclassified as Upper Greensand (Bristow et al., 1997).

In the Isle of Wight, White (1921) recorded 50- 65 m of Lower Chalk, corresponding to Glauconitic Marl (c. 1.25 m-3.7 m), Chalk Marl (c. 15-34 m), Grey Chalk (c. 24-27m) and Plenus Marls (c. 1.5-2.8 m). Kennedy (1969) gave a detailed account of the successions at Culver Cliff [SZ 630 855] and Compton Bay [SZ 365 854], and demonstrated the presence of key marker horizons, including acmes of the brachiopod Orbirhynchia mantelliana and the presence of Jukes-Browne Bed 7.

Macrofossil Biozonation: M. mantelli Zone, M. dixoni Zone, C. inerme Zone, A. rhotomagense Zone, A. jukesbrownei Zone, C. guerangeri Zone, M. gelinianum Zone (pars)

Correlation: see Correlation with other Southern Region Chalk Group classifications

see Correlation with other UK Chalk Group successions

References[edit]

BRISTOW, C. R., MORTIMORE, R. N. & WOOD, C. J. 1997. Lithostratigraphy for mapping the Chalk of southern England. Proceedings of the Geologists' Association, Vol. 108, 293-315.

KENNEDY, W J.1969. The correlation of the Lower Chalk of south-east England. Proceedings of the Geologists' Association, Vol. 80, 459 - 560.

WHITE, H J O. 1921. A short account of the geology of the Isle of Wight. Memoirs of the Geological Survey of Great Britain.

See: Glauconitic Marl, Chalk Marl, Grey Chalk, Plenus Marls, West Melbury Marly Chalk, Zig Zag Chalk, Jukes-Browne Bed 7