• Dewald du Plessis posted an update in the group Group logo of Fossils of GondwanaFossils of Gondwana 2 months, 1 week ago

    2 months, 1 week ago
    2 months, 1 week ago


    The bands in this ironstone provide fossil evidence of seasonal variation in the amount of oxygen produced by microorganisms about 2.6-2.4 bya. The red colouration was caused by the oxidation of dissolved iron. The photosynthesising cyanobacteria, whose activity allowed for the formation of economically important iron deposits, also created extensive dolomite reefs throughout the shallow seas of Precambrian South Africa.