Chronostratigraphy of the Chalk Group - Coniacian Stage
The Coniacian stage was first defined by Coquand (1857), with the type area near Cognac, France. Subsequently, the Salzgitter-Salder Quarry section, Lower Saxony, Germany, has been recommended as the Turonian-Coniacian boundary stratotype (Kauffman et al., 1996).
Definition of base of stage
The first occurrence of the inoceramid bivalve Cremnoceramus rotundatus sensu Tröger non Fiege (= Cremnoceramus deformis erectus) (Kauffman et al., 1996)
Constituent Chalk Group lithostratigraphical units in the UK
Integrated southern England Chalk Group lithostratigraphy: Lewes Nodular Chalk Formation (pars) and Seaford Chalk Formation (pars)
Northern England: Burnham Chalk Formation (pars)
East Anglia: Upper Chalk (pars)
N. Ireland: Coniacian strata do not form part of the Chalk Group
North Sea: Mackerel Formation (pars)
|CONIACIAN||M.coranguinum (pars)||Lower H.rostrata Zone|
(Northern England only)
|.||← s.plana (pars)|
Lithostratigraphical marker-beds for the base of the stage
Southern England: base of the Navigation Hardground
Northern England: interval between Kiplingcotes Marls 1& 2 (Gaunt et al., 1992).
East Anglia: base of Top Rock (where present); perhaps locally in the Bury St. Edmunds district it is marked by a group of closely spaced, iron-stained, spongiferous nodular chalk beds (Bristow, 1990); a hardground at 432.03 m depth in the BGS Trunch Borehole [TG 2933 3455], north Norfolk, is inferred to represent the Navigation Hardground (Wood et al., 1994).
BRISTOW, C. R. 1990. Geology of the country around Bury St Edmunds. Memoir of the British Geological Survey, England & Wales (Sheet 189).
COQUAND, H. 1857. Position des Ostrea columba et biauriculata dans le groupe de la craie inférieure. Bulletin de la Société géologique de France (2), 14, 745-766.
KAUFFMAN, E G, KENNEDY, W J, WOOD, C J. 1996. The Coniacian stage and substage boundaries. Bulletin de l'Institut Royal des Sciences Naturelles de Belgique, 66-Supp, 81-94.
GAUNT, G D, FLETCHER, T P & WOOD, C J. 1992. Geology of the country around Kingston-upon-Hull and Brigg. Memoir of the British Geological Survey.
WOOD, C J, MORTER, A A & GALLOIS, R W. Appendix 1: Upper Cretaceous stratigraphy of the Trunch Borehole. In ARTHURTON, R S, BOOTH, S J, MORIGI, A N, ABBOTT, M A W & WOOD, C J. 1994. Geology of the country around Great Yarmouth. Memoir of the British Geological Survey.