Conditions of Depositional Environment of the Sargelu Formation in Rania Area Based on Geochemical Data

The sequence of the Sargleu Formation (Middle Jurassic) in the Hangira section is located at the northwestern Sulaymaniyah Governorate center in Rania City, northeastern Iraq. The studied successions consist of well-bedded limestone and dolomitic limestone, gray in color, interbedded with thin beds of argillaceous limestone rich in organic matter and intertwined at the top of this succession by thin beds of brown chert rich in ammonite fossils. The aforementioned beds are followed by a succession of thin-bedded limestone, brown color alternating with beds of argillaceous limestone and thin beds of chert. The selected section has been studied in terms of geochemical data of some major and trace elements and the ratio between them for ten samples to elucidate the paleoenvironmental conditions, including paleoproductivity, oxidation and reduction conditions, provenance, hydrodynamic conditions, and detrital input. The productivity record of (P/Al, P/Ti, Ba/Al ratios) indicates high paleoproductivity. Redox proxies for trace elements (V/V+Ni), (U/Th), and (Ni/Co) suggest anoxic to oxygen-deficient conditions. The provenance proxies (Al2O3/TiO2 ratio) indicate that the source rocks of the Sargelu Formation are intermediate igneous rocks. The (Zr/Rb ratio) values indicate a deposition in conditions with low water energy. The high ratios of (Si/Al and Ti/Al) indicate a high clastic flow in the sedimentation basin of the Sargelu Formation due to the presence of detrital quartz or organic silica of organisms with a silicate wall, such as Radiolaria. While the high ratio of (K/Al) is attributed to the role of the wind source of clastic flow in the deposits of the formation, or to the nature of the clay minerals present in the deposits of the Sargelu Formation.