The Sea of the chalk
The chalk was deposited in various epicontinental seas, (that is to say based on a continental crust). On the North American continent, it is found in the Interior Basin (Western Interior Seaway), in particular in Texas.
In Western Europe, she extends widely from England to Russia and to the Middle East. We also find her in the southern hemisphere (western Australia). The depth of deposit generally estimated for typical chalks is understood between 100 and 300 meters.
The epicontinental seas, must paradoxically their evolution to the phenomena occurring in the middle of the oceans, at the level of the oceanic ridges. These vast reliefs submarines swell or sag depending on the magmatic activity, strong or weak, which operates over the rifts.
During the Cretaceous, the Atlantic ocean continues to widen.
The following figure shows well, that between the opening Atlantic Ocean and the closing Ocean Tethys, there are a number of essentially continental microplates caught between Eurasia and Africa, relatively mobile. Between the two yellow lines, the warm seas are the seat of a carbonate sedimentation. The sea of the chalk is one of those seas, installed on the European continent, itself containing areas of weakness or occur of deformations.
For an interactive vision of the planet in the upper Cretaceous, consult the site Paleomap Project.
In Western Europe, certain zones are doubtless going to remain emerged during all the upper Cretaceous. It is in particular massifs cratonisés during the Hercynian orogénèse. The Sea of the chalk insinuates itself between these massifs. We can recognize coastal marine facies vestiges of borders and in which a detrital fraction silicatée (sandy, marly) is represented (region of Le Mans, for example, close to the Armorican Massif).
The microplate ibéro-briançonnaise (containing Portugal, Spain, the Balearic Islands, Sardinia, Péloritains, Calabria Southern, Corsica, Moors) undergoes a left-hand drift with regard to the European plate. Ponds transtension (Pyrenean ponds, south-Provençal pond) form between the Cantabrian Pond in him W and the pond of Valais in him E. The Sea of the chalk could communicate towards him with the seas of the domain of the Pre-Alps.
The average level of seas and oceans varied during the upper Cretaceous. This general level is one of parametrize who are going to influence the nature and the thickness of the chalky series.