The recording of oceanic anoxic event al record and the time of this event in the shallow carbonates of the Dariyan Formation in Zargran mountain (Gadvan) section in the east of Shiraz, was studied based on carbon and oxygen isotopes, microfacies and fossil data.
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The recording of oceanic anoxic event al record and the time of this event in the shallow carbonates of the Dariyan Formation in Zargran mountain (Gadvan) section in the east of Shiraz, was studied based on carbon and oxygen isotopes, microfacies and fossil data. In this section, thickness of the Dariyan Formation is 287 m and 191 samples were taken. Based on field data, the sedimentary sequence of this formation, , begins at the base with thick-layered to massive gray limestones containing orbitolinas and rudists, and in the upper parts it includes medium to thick-layered gray limestones including abundant benthic foraminifera, such as orbitolinas. In the mentioned section, based on the study of the embryonic cells of orbitolinas, a late Barmian-early Aptian age was determined for the lower part of this unit, which is the beginning of the formation of anoxic oceanic deposits. The carbon isotope curves between the C3 and C6 curves in the carbonates at the base of the Daryian Formation show disturbances. These changes and the appearance of the Lithocodium-Bacinella facies in this part of the formation confirm the existence of an oceanic anoxic event. The oceanic anoxic event indicates warming of the environment and greenhouse conditions, which was accompanied by abundant rudists in this section and can be a confirmation for the weather conditions of this event.
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