Mid – Miocene Climatic Optimum (MMCO): Stable Isotope storage in the shallow marine setting, Jeribe Formation, Wasit Governorate, Eastern Iraq


  • Mustafa Ali
  • Sa'ad Al-Mashaikie
  • Arsalan Othman


Stable isotope, Jeribe Formation, Monterey excursion, Miocene, Palaeoceanography


One of the most common global features of climate history events' is the long-lasting positive carbon-isotope excursion or “Monterey Excursion.” The global Monterey excursions are recognized in many deep-sea and, recently, in shallow water depth records during the Miocene epoch. However, despite their importance to global climate evolution, they have never been recorded in shallow marine carbonate successions in Iraq. We analyzed the δ 13C and δ 18O to investigate the relationship between the lithostratigraphic units and the deviation of the stable isotopes. The results show a significant relationship between the depositional energy changes and both δ 13C and δ 18O composition. The present paper deals with the variability of the primary isotopic composition of seawater in the shallow water zone. Sedimentary successions of middle Miocene outcropping in the eastern part of Iraq provide an excellent archive of the oxygen and carbon isotopes.  That display the details of oxygen isotope events (Mi‐events), additional information about Mi 2 and Mi 3 zones, reflect significant changes in glaciation. At the same time, carbon isotope maxima (CM‐events) reflect changes in organic carbon burial and refine the Monterey Excursion. Facies analysis revealed several microfacies could be distinguished, reflecting depositional environments including; lagoon, distal inner ramp, patch-reef, supratidal, and inner ramp environments, matching with their isotopes storage differential. The stable isotopes (18O/16O and 13C/12C) provide an excellent archive of the paleoceanography for the Neogene (middle Miocene Transgression) of the Neo-Tethys. Oxygen and carbon isotopic stratigraphy for bulk-rock were analyzed to distinguish Monterey Event and climate optima.