Determining of an oceanic anoxic event and paleoenvironmental conditions of the Gulneri Formation Kirkuk Oilfield, Northern Iraq

Abstract

Stable isotopic geochemistry in relation to major and trace elements geochemistry of core samples from the Gulneri Formation at Kirkuk Oilfield Northern Iraq has been conducted to determine the occurrence of the oceanic anoxic event (OAE2) and reconstruct the paleoenvironmental conditions during this event. Positive values of the stable carbon isotopic data have revealed that temperature is high during deposition accompanied with higher organic productivity and a high rate of organic carbon burial with a decrease in dissolved oxygen in marine environments, whereas, negative oxygen isotopic values indicate deposition in hot, dry, semi-arid environments with salty marine waters and high organic productivity. These results were also supported by geochemical evidence of paleoclimate through C-value and ratios of Sr/Cu, Rb/Sr, and Ga/Rb, paleosalinity using proxies from Ca/Ca+Fe and Sr/Ba ratios, and paleoproductivity using P/Ti, P/Al and barium ratios. The paleoredox proxies from V/(V+Ni), V/Ni, and U/Th ratios and Uδ indicate dominant anoxic conditions. The recorded oceanic anoxic event (OAE2) has been determined through significant excursion in carbon and oxygen isotopic values as well as geochemical proxies within the sequences of the upper part of the formation marking the final stage of the OAE event.