Post-depositional Changes of the Lower-middle Eocene Limestones of the Area between Assiut and Minia, West of the Nile Valley, Egypt

The diagenetic changes of the Lower-Middle Eocene limestones in the area to the west of AssiutMinia Stretch include the following processes: compaction, cementation, neomorphism, silicification, glauconitization and ferrugination. The compaction is represented by mechanical and chemical types. Cementation is either shallow submarine (represented by micrite, fibrous calcite and isopachous calcite cement) or meteoric water (represented by granular spar, and syntaxial overgrowth rim). The recrystallization processes include the aggrading neomorphism of both micrite and skeletal particles (to yield microspar, pseudospar and blocky calcite). The degrading recrystallization (micritization process) of the skeletal particles is exhibited due to their replacing by the micrite produced by the disintegration of the algal components. Silicification process involves the formation of cherts and the selective replacement of the carbonate constituents. The study of the glauconitization and ferrugination processes include their occurrence and origin.