Carbonate production and stratigraphic architecture of shelf-margin wedges (Cretaceous, Vercors): lessons from a stratigraphic modelling approach

This work was presented at the EAGE workshop in Grenoble. Its purpose was to illustrate a stratigraphic modelling approach on a single schematic 2D case and to discuss which sedimentary features are imaged on synthetic seismic sections at different frequencies. The Vercors plateau carbonate sequence, deposited during the Barremian to Early Aptian, was considered. Modelling hypotheses constrained mainly the depositional time length and the geometry of each sequence. In addition, it was assumed that most of the carbonates were produced in situ.

The stratigraphic modelling approach and lessons from the simulation results are presented, followed by a discussion of how stratigraphic modelling can be a helpful tool to validate or question the geological model. In order to reproduce the sequence geometries, rates of carbonate production needed to be changed between regressive and transgressive periods. Simulated sea-level changes do not match the geological estimations from field interpretation but they are in agreement with the magnitude of sea-level curve variations, with the exception of the early Barremian sequences. Qualitative and quantitative results from the model simulations help to question or validate the geological model. Stratigraphic modelling provides some insight into the way the carbonate system may have worked.

Secondly, for a smaller 2D geological model, several synthetic seismic sections were computed using wavelets of different dominant frequencies. The seismic sections are compared to underline what is imaged mainly at the different frequencies. The presence of two characteristic facies were also analysed. Results show the importance of some thin beds inside thick sequences and that certain sequence boundaries may not be visible at all.