Investigating the impact of differential biogenic carbonate production on carbonate system geometries through stratigraphic forward modelling: The Llucmajor example.

The geometry of carbonate systems reflects the interaction of several factors. Although efforts have been made at investigating the controls on biogenic carbonate system evolution, the impact of the interaction of different carbonate producing biotas is still not fully understood. In this study, we developed a 4D stratigraphic forward models (SFM) of the Miocene Llucmajor platform coupled with sensitivity analysis to examine the effect on platform geometry of changes of the dominant biotic production in the oligophotic and euphotic zones. Our results indicate that the geometry of the platform is impacted by a complex interaction between carbonate production rates, variations in bathymetry, and changes in accommodation. Progradation in the platform model is mainly controlled by oligophotic production of rhodalgal sediments during the lowstands. This study also shows that platform geometry and internal architecture is significantly impacted by the interaction of the predominant carbonate producing biotas. The input parameters for this study are based on well-understood Miocene carbonate biotas with characteristic euphotic, oligophotic and photo-independent carbonate production in which it is essential to explicitly model each carbonate producing class within the simulation run and not averaged with a single carbonate production-depth profile. This distinction is particularly crucial for subsurface exploration studies that rely on stratigraphic forward models, where the overall platform geometry may be approximated through calibration runs and constrained by seismic surveys and wellbores. However, the internal architecture could be over-simplified, without an in-depth understanding of the target carbonate system such as is provided by this study.