Depositional environment and diagenesis of the Khan Formation sandstones in Cheshmeh Bakhshi and Chahroof sections, Posht-e-Badam block

Siliciclastic-carbonate successions of Khan Formation with Permian age are exposed in Posht-e- Badam block, located in southwest of Tabas. The siliciclastic deposits of this formation in Cheshmeh Bakhshi and Chahroof sections mainly consist of medium to fine quartzarenite sandstones with high compositional and textural maturity. Planner and trough cross beddings and parallel laminations in these sandstones represent sedimentation in a high energy shoreface environment with influence of waves energy. Four lithofacies comprising foreshore, upper shoreface, erosional channel and storm deposits are recognized. Based on petrography, cathodoluminescence and SEM images, early and late diagenetic features were recognized. Cathodoluminescence images of carbonate cements in sandstones show that cementation has been occurred in one phase from meteoric waters during early diagenesis. Also SEM images and EDX analysis imply producing of chlorite from converting of primary ferric clays and so as a rim over grains during late diagenese stage. Other diagenetic features are compaction (physical and chemical), stylolitization, silica and carbonate cementation, solution and replacement of clastic grains.