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

From Earthwise
Jump to navigation Jump to search

The New Pit Beds (holostratotype: Beachy Head [TV 588 964] ), named after New Pit Quarry [TQ 424 113] near Lewes, comprise massively bedded, smooth textured chalk, containing conspicuous marl seams. They are 40-45 m thick in East Sussex, and equate with the interval from the Malling Street Marls at the base to the lowest of the Glynde Marls at the top. Other key marker marls are (in ascending order) the Lighthouse Marls, the Iford Marls, and the three thick New Pit Marls in the higher part of the succession (Mortimore, 1986a). Two localities near Lewes, at Glyndebourne [TQ 4484 1018] and Southerham Limeworks [TQ 424 093] show the development of anomalous successions. At Glyndebourne six hardgrounds (named the Glyndebourne Hardgrounds) extend from the top of the Holywell Beds into the lower part of the New Pit Beds, and at Southerham Limeworks, phosphatic chalk overlies a massive, 0.7 m thick hardground, named Strahan's Hardground (Lake et al., 1987). The latter hardground falls between New Pit Marls 1 and 3, and is overlain by an anomalously flinty chalk succession (Lake et al., 1987; Mortimore, 1997).

The New Pit Beds are less fossiliferous than the Holywell Beds. The fauna is mainly dominated by brachiopods (terebratulids and the small Terebratulina lata) and inoceramid bivalves, particularly Inoceramus lamarcki and I. cuvieri (Mortimore, 1986a). The echinoid Conulus subrotundus is locally common in the lower and middle parts of the succession (Mortimore, 1986a).

Macrofossil Biozonation: T. lata Zone (pars)

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.

MORTIMORE, R N.1997. The Chalk of Sussex and Kent. Geologists’ Association Guide No. 57. (Bath: The Geologists’ Association.)

See: marl, flint, hardground, phosphatic chalk