Earliest skeletal fossils from Precambrian–Cambrian boundary strata, Elburz Mountains, Iran

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Abstract
The lithological and biotic succession across the late Precambrian to early Cambrian interval is outlined for the Dalir and Valiabad successions of the Elburz Mountains of Iran. The Lower Dolomite Member contains an assemblage of phosphatic tubes and other poorly preserved remains. The succeeding Lower Shale Member bears macroscopic chuariamorphid algae. Early skeletal fossil diversity rises through the Middle Dolomite Member, with the successive appearance ofProtohertzina anabarica, Cambrotubulus decurvatusandAnabarites trisulcatus, culminating near the top of the dolomites with the appearance ofPurellasp.,Maikhanella multa, Tiksitheca licisand circothecids. This succession is compared with lower to upper parts of the Nemakit-Daldyn Formation of Siberia. The overlying Upper Shale Member bears phosphatic beds at its base with allathecids and an uncoiled pelagiellid (?Aldanellasp.) that suggest comparison with lower Tommotian strata and the Precambrian–Cambrian boundary phosphorite event of southern and central Asia. A rich assemblage of molluscs appears high in the Upper Shale Member, including theLatouchella korobkovigroup and thePelagiella lorenzigroup. The succession is broadly homotaxial with those from the Siberian Platform and Mongolia and those platforms bordering Gondwana (India, Kazakhstan, South China).