Geochemical and Digenetic controls on the Dammam Formation in the Southern Desert of Iraq

The integrated geochemical and diagenesis process provide valuable understandings into the depositional environments and mineral resources of the Eocene succession in the region, supporting both geological understanding and economic exploration efforts. This research utilizes geochemical and petrographic analyses of sediment samples (24 core samples) from the Dammam Formation in southern Iraq to reconstruct paleoenvironmental conditions during the Eocene epoch. The formation is primarily composed of carbonate lithology, predominantly limestone with dolomitic and fossiliferous strata, and exhibits evidence of extensive diagenetic alterations such as dolomitization, silicification and other processes. Geochemical data reveal high concentrations of calcium and magnesium oxides, consistent with carbonate-rich, shallow marine depositional environments. Notably, the presence of unconformities at the boundaries with the Euphrates and Rus formations indicates depositional hiatuses likely linked to sea-level fluctuations. Elemental correlations suggest a dominant marine influence with limited terrigenous input, as reflected in the low concentrations of SiO₂, Al₂O₃, Fe₂O₃, and alkali oxides. Variations in sulfate oxides and the occurrence of gypsum nodules point to fluctuating salinity conditions, possibly related to lagoonal or restricted platform environments. Silicification processes, especially in the central regions of the formation, involve silica filling voids and replacing carbonate minerals, indicating diagenetic silica enrichment during lithification. The presence of red-stained marl zones and iron oxides signifies oxidative, coastal, peritidal settings. Overall, the integrated geochemical and petrographic evidence supports interpretations of a dynamic depositional environment characterized by shallow marine, lagoonal, and restricted platform conditions, which reflect significant sea-level changes during the Eocene and contribute to understanding regional sedimentation and diagenetic histories.