The solidity and porosity of calcium carbonate rocks are of major interest for oil-reservoir evaluation, groundwater flow studies, and civil engineering applications. Micritization—an early diagenetic process that converts carbonate shells and skeletal grains into microcrystalline carbonate—significantly affects these rock properties, yet its underlying mechanisms remain poorly constrained. The coastal environments of Abu Dhabi provide natural laboratories for studying micritization, as they are modern analogues of the low-angle carbonate ramps that were widespread in epeiric seas throughout much of the geological past.
In this study, we investigate calcium carbonate muds and associated pore waters from a range of depositional environments, including mangroves, tidal channels, sabkhas, and offshore settings, to better understand the processes controlling micritization. We apply an integrated approach combining sedimentological, mineralogical, and geochemical methods. Preliminary results indicate that the carbonate mud is predominantly composed of aragonite, with minor amounts of low magnesium calcite. Boring intensity increases with depth, particularly in tidal-channel environments, and is closely associated with physical erosion by endolithic fauna. In contrast, crystal morphologies observed in sabkha sediments suggest that chemical precipitation processes are more dominant in these settings.

Trace element systematics reveal that micritization is accompanied by systematic changes in Sr/Ca and Mg/Ca ratios. In all tested environments, grain size reduction (i.e., micritization) is associated with a significant increase in Mg/Ca, while Sr/Ca is much less sensitive to the same process. While both Sr/Ca and Mg/Ca are incorporated within the diagenetic aragonite lattice according to their respective partition coefficients, Mg/Ca ratios are strongly increased by adsorption during micritization-related grain size changes. The decoupling of Mg and Sr during the micritization process may provide new constraints on the question of the mechanism of micrite formation.