Southern Province Chalk nomenclature - White Chalk Subgroup: Newhaven Chalk Formation

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Name

First proposed in Rawson, Allen and Gale (2001) as part of the agreed standard for the Chalk Group of England. The term Newhaven Chalk Member was used by Mortimore (1987) as part of his Sussex White Chalk Formation and adopted as the Newhaven Chalk Member within the Upper Chalk Formation by Bristow, Mortimore and Wood (1997).

Type section

Seaford Head [TV 496 976] in Sussex.

Primary Reference Section

Newhaven [TV 446 999] to Brighton [TQ 338 033] cliffs Sussex; Paulsgrove Pit [SU 635 065] on Portsdown; Whitecliff Bay [SZ 638 854] on the Isle of Wight; White Ness [TR 397 710] to Foreness Point [TR 383 717] and Margate [TR 354 714] on the Thanet Coast in Kent; Ballard Point [SZ 048 813] and White Nothe [SY 764 813] in Dorset.

Formal subdivision

None herein. Informally includes a number of laterally persistent flint and marl beds named in Mortimore (1986) that can be traced outside Sussex in the Southern and Transitional provinces.

Lithology

Composed of soft to medium hard, smooth white chalks with numerous marl seams and flint bands, including abundant Zoophycos flints (notably at levels near the base). The formation is known to contain distinct phosphatic chalks of limited lateral extent. Equivalent beds, the Margate Chalk of north Kent, are marl-free and contain little flint.

Definition of upper boundary

Placed at the Castle Hill Marl 2 in the type locality at Seaford Head, Sussex where there is some evidence of a reduction in marl thickness over a structural high. In expanded trough areas a higher set of marls, the Pepper Box Marls, are well developed and the boundary is taken at this level.

Definition of lower boundary

Conformable at the Buckle Marl 1 in the Sussex succession. The incoming of common Zoophycos flints and the presence of the zonal Uintacrinus socialis crinoid at the base of the Newhaven Chalk Formation are useful indicators in the field.

Thickness

45 to 75m in the basinal sequences of the Southern Province. Limited by sub-Palaeogene erosion over large areas of Southern Britain.

Distribution

Known throughout the Southern Province northward to the Pewsey/Kingsclere structure and as limited outliers north of this structure. Its presence within the Chilterns and northward into East Anglia in the Transitional Province is not well known.

Previous names

Newhaven Chalk Member of Mortimore (1986) and as adopted in Bristow et al. (1997). Broadly equivalent to the Margate Chalk Member of the Ramsgate Chalk Formation of Robinson (1986) in Kent.

Parent

White Chalk Subgroup.

Age and biostratigraphy

Upper Cretaceous, Santonian to Campanian. Uintacrinus socialis, Marsupites testudinarius, Uintacrinus anglicus and Offaster pilula Zones.

References

Rawson, Allen and Gale (2001); Bristow et al. (1999); Bristow, Mortimore and Wood (1997).

Margate Chalk Member

Name

Defined in Robinson (1996). Herein taken as the modified classification in Bristow, Mortimore and Wood (1997).

Type section

North Foreland [TR 398705] to Foreness Point [TR 385 717] and Palm Bay [TR 380 715] on the Isle of Thanet, north Kent.

Primary Reference Section

As above

Formal subdivision

None herein. Informally includes a number of laterally persistent flint and marl beds named in Robinson (1986) which can be traced outside Kent in the Southern and Transitional provinces where they are correlated with the named beds of Mortimore (1986)

Lithology

Marl-free smooth white chalk with little flint, weakly developed indurated iron-stained sponge beds.

Definition of upper boundary

Limited by sub-Palaeogene erosion surface in the Isle of Thanet.

Definition of lower boundary

Conformable at the surface immediately above the Barrois Sponge Bed in Thanet (Robinson, 1986).

Thickness

Up to 24m in the North Foreland to Foreness Point and Palm Bay sections on the Isle of Thanet in north Kent.

Distribution

Confined to the Thanet area of Kent and possible northwards into Essex and southern East Anglia

Previous names

Margate Member of the Ramsgate Chalk Formation of Robinson (1986). The ‘Margate Chalk’ of Whitaker (1865a, 1872). Margate Chalk Formation definition in BGS lexicon. Lateral equivalent of the greater part of the Newhaven Chalk Formation. The lateral extent of this member is not known and may well be confined to the Thanet area although there are indications of this lithology in Essex.

Parent

Newhaven Chalk Formation.

Age and biostratigraphy

Upper Cretaceous, Santonian to basal Campanian. Micraster coranguinum, Uintacrinus socialis, Marsupites testudinarius and Uintacrinus anglicus Zones.

References

Bristow, Mortimore and Wood (1997); Robinson (1986); Dowker (1870); Gale, Wood and Bromley (1987); Mortimore, Wood and Gallois (2001).