The Cretaceous

The chalk cliffs of Normandy deposited in the course of a geological period, the Cretaceous, which extends from - 145.5 ± 4 to - 65.5 ± 0.3 million years ago. The Cretaceous name comes from the latin "creta" which means "chalk", name given by Omalius d' Halloy, French geologist.

Le Crétacé

The Cretaceous in the scale of the fossiliferous times, the absolute datings are not any more the ones adopted today.

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In fact, the chalk of the anglo-norman basin only extends in the upper part of the Cretaceous.

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Subdivisions in floors of the Cretaceous period

The Cretaceous, according to the charter chronostratigraphique international, international committee, in August, 2012

The floors of the upper Cretaceous recover the intervals of next times (IUGS, on 2013))
· Maastrichtien (72,1 ± 0,2 - 66 My)
· Campanien (83,6 ± 0,2 - 72,1 ± 0,2 My)
· Santonien (86,3 ± 0,2 - 83,6 ± 0,2 My)
· Coniacien (89,8 ± 0,3 - 86,3 ± 0,5 My)
· Turonien (93,9 - 89,8 ± 0,3 My)
· Cénomanien (100,5 - 93,9 My))
The Upper Campanian and the upper Maastrichtian are not represented in the French chalk cliffs.

The International Committee of Stratigraphy (Gradstein and al ., on 1994) specifies the durations:

  • Turonien: 4,2 My
  • Coniacien: 3,5 My
  • Santonien: 2,3 My

During the upper Cretaceous occurs a world rise of the level of seas. This transgression gets organized in two cycles of the second order:

  • From lower Cénomanien, the sea advances gradually on the continent,
  • At the beginning of Turonien, the transgression becomes widespread.