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This study integrates ichnological and sedimentological data to interpret depositional environments in the carbonate sediments of the Mobarak Fm. (Lower Carboniferous) in the Alborz Mountains of northern Iran. Seven ichnofabrics including Thalassinoides (Th), Zoophycos‒Phycosiphon (Zo-Ph), Skolithos‒Thalassinoides (Sk-Th), Zoophycos‒Diplocraterion (Zo-Di), Thalassinoides‒Rhizocorallium (Th-Rh), Zoophycos‒Arenicolites (Zo-Ar) and Chondrites‒Phycosiphon (Ch-Ph) have been identified in the studied succession. Th ichnofabric is characterised by the dominance of the deposit-feeding trace fossils, revealing low sedimentation rate and activity of the organisms in a loose substrate. Vertical succession of the Zo-Ph, Sk-Th and Zo-Di ichnofabrics indicates change in the firmness of the substrate. Th-Rh and Zo-Ar ichnofabrics reveal two different energy phases including a lower energy condition with the activity of deposit-feeders and a higher energy phase identified by the activity of suspension-feeders. Ch-Ph ichnofabric is characterised by low diversity and low abundance of trace fossils that were identified in black, limy shale, displaying a long lasting outer ramp setting with low energy, low sedimentation rate, and dysoxic-anoxic conditions of the substrate. Ichnological features of the Mobarak Fm. are controlled by subsidence-inducing changes in the accommodation space of the depositional system dictating variations in paleoenvironmental conditions such as oxygen levels and hydrodynamic energy. [ABSTRACT FROM AUTHOR]

Despite belonging to an important time slice in the geological history, the Eocene shallow-marine beds of the Alborz region in Iran have received little attention from researchers. We selected two stratigraphic sections (Mojen and Kalateh) ascribed to the Ziarat Formation as suitable representatives for the current analysis, emphasising on their constituent microfacies and paleoenvironmental implications. The biotic communities are characterised by larger benthic foraminifera (LBF), coralline algae, corals, and bivalves as the major carbonate facies components. The microfacies gradients and paleoenvironmental analysis suggest deposition in a shallow-marine oligotrophic ramp environment within two platform stages. Both these stages indicate an increase in water depth from the inner to the middle ramp settings with spatial distribution of the LBF and other benthic components. Our data support the previous view that the early Eocene witnessed an increase in LBF taxa with near obliteration of the coral reefs in the sedimentary platforms across the Tethys. The corals reinitiated building reefal structures in the Middle Eocene, marking an important phase in the Tethyan paleoenvironmental evolution. [ABSTRACT FROM AUTHOR]