A HISTORY OF TOURAINE THROUGH ITS ROCKS
6 - IN SENONIAN

Simplified stratigraphical scale (the millions of years (MY) correspond to the period's beginning) :

4500 MY 540 MY 250 MY 65 MY
Eras Precambrian Paleozoic (primary era) Mesozoic (secondary era) Cenozoic (tertiary + quaternary eras)
Periods Triassic Jurassic Cretaceous
Epochs lower Cretaceous upper Cretaceous
96 MY 92 MY 88 MY
Stages Cenomanian Turonian Senonian

The sea, still present, is going to withdraw gradually...
The sea deposits several types of sediments:
       - a white chalk with flint (called also chalk of Blois) corresponding to a rather deep sea,
       - a sandstone-like and very fossiliferous limestone, deposited in more coastal environment (the chalk of Villedieu),
       - quartzose sands in the southwest of Touraine (sands of Balesmes),
       - and clayey-siliceous formations : clays, flints and spongolites (spongolite = siliceous rock rich in sponges spicules).


Flint and chalk of Blois - Origin: Monts


Chalk of Villedieu with fragment of internal mould of ammonite - origin: Langeais


Sands of Balesmes - Origin: Descartes


Spongolite coming from clayey-siliceous formations (with fragments of sponges) - origin: Pont-Boutard

The sea withdraws before the end of Senonian and the last deposits are constituted by the clayey-siliceous formations. In these formations, the importance of the siliceous fraction corresponds to important contributions from the close continents, what reveales a little deep sea.
Senonian fossils are varied: molluscs, brachiopods, sea urchins and, into the formations rich in silica, numerous sponges.

Several fossils are visible on pages dedicated to Senonian.
See also other comments on Senonian.

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The natural context   Touraine's Depths   From Oxfordian to lower Cretaceous   In Cenomanian   In Turonian   In Senonian   In Paleogene   In Neogene   In Quaternary   Map of Indre-et-Loire   Simplified geological map (north)   Simplified geological map (south)

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