Interpretation of the sedimentary environment of the Turonian–Coniacian Khasib Formation, using geochemical and petrological analyses

In this study, seven core carbonate samples were collected from the marine Upper Cretaceous (Turonian– Coniacian) limestone in two wells in the East Baghdad Oilfield of the Mesopotamian Basin. The Turonian– Coniacian period is regarded as the archetypal warm interval as well as a pivotal epoch in biological evolution. The carbonate strata of the Khasib Formation in the East Baghdad Oilfield of the Mesopotamian Basin were chosen as a model. The paleoenvironment was reconstructed using petrological characteristics and concentrations of major, trace, and rare earth elements (REEs), as well as carbon, oxygen, and strontium isotopic studies. The data suggest that the paleotemperature of the seawater was 28ºC, that suboxic-anoxic paleoredox conditions were present, that the paleosalinity of the seawater was minimal, and a biological explosion occurred when the temperature dropped to a point where life could survive. Dolomite dissolution, influenced by early meteoric water, established the groundwork for high-quality reservoirs, and leftover dolomite also protected natural oil. This research adds to the paleoenvironmental record and offers a theoretical foundation for future natural oil exploitation.