Carbon isotope anomaly of the “Yellow Beds” in the Lower Cambrian Mila Formation in Shahmirzad, Alborz, northern Iran

For the “Yellow beds” occur in the Member 1 of the Lower Cambrian Mila Formation in northern Iran, which consists mainly of stromatolitic and algal dolostone. The beds include conspicuous sedimentary structures including crusts formed in an evaporating condition. Based on the lithology, mineral composition, carbon, oxygen, and Sr isotopes, the “Yellow beds” are regarded as the terrestrial deposits on an arid land. Their heavy δ18O indicates evaporation and the light δ13C may imply a characteristic of terrestrial carbonate. The “Yellow beds” represent subaerial deposits, likely paleo-soil profile, and were deposited in periods of sea-level low during early Cambrian.