The Skillogalee Dolomite is a 750 million-year-old formation that is host to stromatolite fossils – the only evidence of complex living organisms at that time. Stromatolites are fossilised biochemical accretionary structures created by Cyanobacteria (‘blue-green algae’) colonies which form microbial mats and laminated mounds in shallow saline waters. Living stromatolites are found at the tip of the Yorke Peninsula (SA) and Shark Bay in (WA).
Skillogalee Dolomite includes blue-grey dolomites, magnesites, bands of black cherts and stromatolites. Magnesites (magnesium carbonate) of this formation were formed in marginal lagoons of the Adelaide Geosyncline around 750 million years ago and occur as beds, commonly conglomerate in texture, as pictured below.
Kaolinite is a white soft mineral created by hydrothermal alteration or weathering of formations such as this example of Skillogalee Dolomite at Arkaroola.
