Geochemical and Petrographic characterization of dolomitized carbonates in Kawagarh Formation, Northern Pakistan

Late Cretaceous Kawagarh Formation, from Hazara Basin of northern Pakistan, exhibit extensive diagenesis including dolomitization, which significantly impacts its reservoir potential. In this study we investigated the processes that drove dolomitization in Kawagarh Formation through integration of petrographic analysis and carbon-oxygen isotope geochemistry. Thin sections optical microscopy revealed various dolomite textures, including planar-euhedral and non-planar-anhedral crystals, as well as evidence of recrystallization and porosity enhancement. Multiple textural indicated the multiple phases of dolomitization associated with variable diagenetic conditions.

Carbon (δ¹³C ) and oxygen (δ¹⁸O) isotope analysis of dolomite showed the distinct geochemical signatures indicative of dolomitizing fluid sources. These isotopes suggested a mixed origin, involving marine and meteoric fluids, with potential contributions from hypersaline brines during burial diagenesis. The spatial and isotopic variability suggested that dolomitization was influenced by tectonic activity and stratigraphic controls, which resulted in highly heterogeneous in porosity and permeability.

The findings from this study provided new insights into the diagenetic history of the Kawagarh Formation and enriched our conception of dolomitization mechanisms in analogous settings. The study highlighted the critical role of integrated petrographic and isotopic approaches in unraveling complex diagenetic processes, with implications for reservoir characterization and hydrocarbon exploration.