Intracratonic basins : subtle records of long wavelength deformations and eustasy - the case example of the paris basin
Résumé
Subtle vertical movements, major constraints for lithospheric and
mantle dynamics models, are difficult to quantify and to date. In sedimentary
basins, this quantification is based on subsidence measurements
by backstripping. The error bars on this technique can be high,
mainly in the low subsiding domains were dates, water depths and eustasy
are important data.
We developed a 3D high-resolution method of accommodation space
measurement at the scale of intracratonic basins, with a precise quantification
of the water depth. Based on this 3D quantification of the
accommodation, it was possible to discriminate the deformation and
the eustatic controls based on the principle that the basin-scale signal
contain the eustasy and the local control is of tectonic origin.
(1) The application of this technique to the Paris Basin questioned the
importance of the long term subsidence signal versus major deformation
events of at least European-scale (Mid and Neo-Cimmerian, Austrian,
Senonian deformations..) that control, in the Paris Basin, major subsidence
centers reorganization.
(2) The stratigraphic record of the Paris Basin, with those excellent datings
(inheritance of 2 centuries of biostratigraphy), is also a unique
place for constraining eustasy, its timing (with now a good knowledge
of the sea water temperatures since the Jurassic) and the order of magnitude
of the sea level variations. Back, those sea level amplitude
constraints can be inputs for a better quantification of the vertical movements.