Carbonate diagenesis of the mixed clastic-carbonate Galala Formation, North Eastern Desert, Egypt

The carbonate diagenetic history of the Late Cenomanian Galala Formation (North Eastern Desert, Egypt) successively includes marine-phreatic, mixed marine-meteoric, meteoric-phreatic, and subaerial diagenesis. The marine-phreatic diagenesis proceeded through the following path: (a) micritization of skeletal allochems; (b) shallow marine cementation (fibrous calcite and circumgranular spar cements); and (c) dolomitization of the lime mud to fine-crystalline dolostone (dolomicrite). The mixing marine-meteoric diagenesis was associated with the formation of the coarse-crystalline dolostone (dolosparite) by the aggrading recrystallization of the precursor dolomicrite. The meteoric-phreatic diagenesis comprises of the following consecutive stages: (a) the development of granular calcite, blocky calcite, and syntaxial rim cements; and (b) the recrystallization of both the carbonate matrix and bioclasts. The subaerial diagenesis is responsible for the calcitization of the precursor dolomites; whereas, the percolation of meteoric water results in the removal of the Mg ions from the dolostone and the production of calcite.