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

Abstract

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.