Palaeoenvironment Conditions During Deposition of Sargelu, Naokelekan, and Najmah Formations in Zey Gawara Area, Kurdistan Region, Iraq: Implications from Major and Trace Elements Proportions

Abstract

Palaeoenvironment conditions during deposition of Jurassic Sargelu, Naokelekan, and Najmah formations were studied based on samples from well Z1 in Zey Gawara area, Kurdistan region, Iraq. For the purpose of determining the palaeoredox, palaeoclimate conditions as well as palaeoweathering, tectonic setting, and provenance indices, the inorganic geochemical analysis to indicate the number and amount of different elements were performed. Based on the occurrence and proportionalities of trace elements e.g., V, Ni, Cu, Sr, the Sargelu Formation was probably accumulated in suboxic to anoxic conditions, while the Naokelekan and Najmah formations were deposited under the suboxic to dysoxic conditions. Relatively semiarid condition have suggested for Sargelu and Naokelekan formations, and relatively semi humid condition for Najmah Formation. The chemical index of alteration and the high plagioclase index of alteration suggest for modest to intense weathering source area for the Sargelu and Naokelekan formations. The index of chemical variability (<1) implies that the Sargelu, Naokelekan, and Najmah formations are probably immature sediments and deposited inside a tectonically active setting. Based on the tectonic indicators, the Sargelu and Naokelekan formations were deposited in an active continental margin, and the Najmah Formation was deposited in an oceanic island arc. The felsic for the Sargelu and Naokelekan and the felsic- intermediate igneous rocks were proposed as plausible source rocks for the Najmah Formation.