Geochemical analysis of evaporite sedimentation in the Gachsaran Formation, Zeloi oil field, Southwest Iran

In this study, the paleo-sedimentary depositional environment of the Gachsaran Formation and the Asmari reservoir cap rock (i.e., the stratigraphically lowest member of the Gachsaran Formation) was investigated from elemental geochemical data and mineralogical data obtained XRF and SEM analyses, respectively, of anhydrite samples collected from two oil wells in the Zeloi oil field in southwestern Iran. The present data reveal that arid conditions and cycles of transgression–regression of the sea contributed to the formation of evaporite sequences of the Gachsaran Formation in a coastal sabkha-lagoon basin that was partly closed to the sea. This interpretation was based on synthesis of statistical correlation analysis the geochemical data, chemostratigraphic correlation of geochemical ratios, and textural analysis of salts observed in SEM images.