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

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The Spetisbury Chalk, c. 25-30 m thick, named after Spetisbury, near Blandford Forum, Dorset, comprises firm, white, flinty chalk, including large, tabular flints near the base, and Zoophycos flints (Précy Zoophycos of Mortimore & Pomerol, 1987) and locally large nodular flints associated with abundant inoceramid shell debris, towards the top (Bristow et al., 1997). The base of the unit is a positive topographic feature which biostratigraphical evidence suggests is at about the level of the Whitecliff Flint, at the junction of the Sompting Beds and Whitecliff Beds of Mortimore (1986a) (Bristow et al., 1997). The top of the Spetisbury Chalk is marked by the negative feature at the base of an escarpment formed by the overlying Portsdown Chalk (Bristow et al., 1997). This feature appears to be caused by an upward change to sparsely flinty chalk, and is approximately coincident with the Portsdown Marl of Mortimore (1986a), thus making the Spetisbury Chalk approximately coeval with the Whitecliff Beds in the upper Culver Chalk of Mortimore (1986a) (Bristow et al., 1997).

Macrofossil Biozonation: upper G. quadrata Zone (pars) (post Applinocrinus Beds pars)

Correlation: see Correlation with other Southern Region successions

see Correlation with other UK 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.

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

MORTIMORE, R N & POMEROL, B. 1987. Correlation of the Upper Cretaceous White Chalk (Turonian to Campanian) in the Anglo-Paris Basin. Proceedings of the Geologists' Association. Vol. 98 (2), 97-143.

See: flint, Précy Zoophycos, Sompting Beds, Whitecliff Beds, Portsdown Chalk (Bristow et al., 1997), Culver Chalk.