Dolomitization of Middle Eocene carbonate rocks, Abu Roash area, Egypt

Dolomitization is the most striking diagenetic process affecting the late Middle Eocene shelly limestone beds at Abu Roash and its neighboring areas. Petrographic investigations reveal that these rocks represent shelly-wackstone to packstone microfacies, that they were deposited probably within a shallow subtidal setting. The rock matrix has been subjected to both selective and complete dolomitization and replaced by equigranular mosaics of fine-to medium-grained dolomite (crystalline planar-s dolomite texture). Meanwhile, the embedded shell fragments show high resistance to dolomitization and their original calcite composition is mostly preserved. The petrographic features of the dolomite texture suggest that these dolomites were formed under near surface and low temperature conditions.