Coniacien

Coniacien

Coniacien is the third of six floors of the upper Cretaceous. He extends of - 89.3 ± 1 My in - 85.8 ± 0.7 My is a rough duration of 3,5 My. The stratotype is defined in Cognac (Charente-Maritime).
The base of Coniacien is defined by the appearance (FAD) of Inocérame (bivalve) Cremnoceramus rotundatus and either by the appearance of the ammonite Forresteria petrocoriensis
His summit is defined by the appearance of Inocérame (bivalve) Cladoceramus undulatoplicatus
Coniacien is the floor the best represented in the cliffs of the Country of Callus:
-EEnter the valleuse of Antiiron (of Etretat) and western , Fécampby way of the Needle of Belval;
-BBetween Fécamp is (high cliff) and western ; Veules-les-Roses
-EEnter the Throat of Small Ailly (low cliff) and Belleville-sur-Mer (high cliff);
-BBetween Criel and Mesnil-valley;
-EEnter the Wood of Cise and Ault.

Cremnoceramus rotundatus would appear in Dover and in Sussex over the hardground navigation, at the level of the marls Navigation.
In the domain thétysien, Coniacien is subdivided into 3 sub-floors on the basis of ammonites:

  • Coniacien inferior: zone to Paratexanites serratomarginatus
  • Coniacien means: zone to Gauthiericeras margae
  • Coniacien superior: zone to Peroniceras tridorsatum

The symposium of Brussels (1995) proposed one subdivision on the basis of inocérames:

  • Coniacien inferior: F.O. of Cremnoceramus rotundatus,
  • Coniacien means: F.O. of the spiral inocérame Volviceramus koeneni,
  • Coniacien superior: F.O. of Magadiceramus subquadratus.

Tröger (1989) propose the following assemblies of inocérames for every subdivision:

  • Coniacien inferior:Inoceramus waltersdorfensis, I. rotundatus Tröger not Fiege, Cremnoceramus deformis, Cr. schloenbachi, Mytiloides incertus.
  • Coniacien means: Inoceramus frechi, I. kleini, I percostatus, Volviceramus involutus, Vo. koeneni and at the beginning of the lineage Platyceramus mantelli sensu Barrois.
  • Coniacien superior:Magadiceramus subquadratus, taxon of the lineage of Platyceramus mantelli sensu Barrois, continuation of the taxon of average Coniacien Volviceramus and in temperate regions the first one taxon of the group Sphenoceramus.

The limits lithostratigraphiques between the subdivisions of Coniacien in England and in the Country of Callus are: