Depositional setting and paleoecology of the Sarmord Formation (Hauterivian-Albian) in selected sections from northeastern Iraq: Microfacies and geochemical implications

Petrographic and diagenetic investigation accompanied with microfacies analysis, major and trace elemental study of the Sarmord Formation in two outcrop sections (Qaiwan and Betwata) from northeastern Iraq were conducted. Calcispheres, benthic foraminifera, radiolaria and bioclasts including skeletal debris of pelecypod and echinoderms are the main skeletal components in addition to intraclasts. The main diagenetic events include; micritization, dissolution, cementation, compaction, dolomitization and formation of authigenic minerals such as pyrite and quartz silicification. The succession of the Sarmord Formation include two main microfacies, which are subdivided into four submicrofacies represented by calcispheres lime mudstone submicrofacies, and lime wackestone microfacies which includes; planktonic foraminifera–radiolarian wackestone, planktonic foraminiferal–calcispheric wackestone and calcisphere–radiolarian wackestone submicrofacie which reflect deposition in toe-of-slope and deep marine environments. Paleoredox proxies of V/V+Ni and V/Ni ratios reflect anoxic prevailed conditions. while paleoclimatic geochemical ratios using Rb/Sr, Sr/Cu and Ga/Rb ratios reflect warm and humid conditions. Geochemical proxies for paleosalinity Sr/Ba ratio indicates a typical marine to intermediate-salinity environment while the Ca/(Ca+Fe) ratio reflects sedimentary between mixed and normal waters, as for the paleoproductivity P/Ti ratio, it was indicated that paleoproductivity was low to moderate, this is consistent with the depositional environment of the Formation, where warm deep marine environment, the geochemical record of the Formation reflects a synergy between global oceanographic events and local paleogeographic controls, where topographic restriction within the Arabian Plate sustained hypoxia