South-west England Chalk Group Lithostratigraphy: Jarvis & Woodroof (1984) & Jarvis & Tocher (1987) - Connetts Hole Nodular Chalk Member
The Connetts Hole Nodular Chalk Member, named after Connetts Hole [SY 234 892], Devon, comprises a laterally variable succession of hard, yellow-stained nodular chalk with hardgrounds and sporadic flints in the upper part (Jarvis & Woodroof, 1984). It is c. 13.5 m thick at White Cliff [SY 233 893], but thins to just a couple of metres elsewhere, and is locally absent (Jarvis & Woodroof, 1984). The base of the Connetts Hole Nodular Chalk is immediately above the upper surface of the Haven Cliff Neocardioceras Hardground, marking the top of the Beer Head Limestone Formation, and the top is defined by Flinty Hardground 5 of Jarvis & Woodroof (1984), or locally where absent, the Branscombe Hardground. A single, conspicuous marl (the West Ebb Marl) seam is a laterally persistent marker in the lower part of the succession, and a strongly indurated hardground higher in the succession (the Branscombe Hardground) is the focus of much localised stratigraphical condensation in the member (Jarvis & Woodroof, 1984). Below the West Ebb Marl, there is the localised occurrence of a smooth-textured freestone, named the Beer Stone, the development of which causes local expansion of the member (Jarvis & Woodroof, 1984). The inoceramid bivalve Mytiloides is locally very abundant, and the brachiopod Orbirhynchia cuvieri is also characteristic.
Macrofossil Biozonation: Jarvis & Woodroof (1984) proposed a largely untested biozonal scheme based on inoceramid bivalves, which is not used herein. Recent work (Woods, 1999) on the successions in south-east Devon shows that the Connetts Hole Member of Jarvis & Woodroof (1984) belongs to the Mytiloides spp. Zone (sensu Wood, 1996).
Correlation: see Correlation with other lithostratigraphical schemes for south-west England
see Correlation with other UK regions
References
JARVIS, I & WOODROOF, P B. 1984. Stratigraphy of the Cenomanian and basal Turonian (Upper Cretaceous) between Branscombe and Seaton, S E Devon, England. Proceedings of the Geologists' Association, Vol. 95 (3), 193-215.
WOOD, C. J. 1996. Upper Cretaceous: the Chalk Group. In SUMBLER, M. G., British Regional Geology: London and the Thames Valley. Fourth Edition. (London: HMSO for the British Geological Survey).
WOODS, M A.1999. Draft contribution to the sheet description of the Sidmouth district (Sheet 326): Cretaceous. British Geological Survey Technical Report, WH/99/28R.
See: Connett's Hole Nodular Chalk Member, Haven Cliff Neocardioceras Hardground, Beer Head Limestone Formation, marl, flint, hardground.