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).
Contents
Definition of base of stage[edit]
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[edit]
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) |
| M.cortestudinarium . |
. | |
| . | ← s.plana (pars) |
Lithostratigraphical marker-beds for the base of the stage[edit]
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).
References[edit]
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.
