Paleosalinity of Ediacaran fossils in South Australia

Ediacaran fossils of South Australia have been interpreted in two contrasting ways: marine invertebrates vs soil lichens. Paleosols with desert roses and eolian interbeds with adhesion warts are two lines of evidence, among many, for non-marine deposition. Geochemical paleosalinity indices provide new tests of these divergent interpretations. Boron content is low in freshwater, but high in marine rocks, and as a paleosalinity proxy can be compared with gallium (freshwater has B/Ga <3). Boron can also be compared with potassium, after correcting for burial alteration using Weaver crystallinity index (freshwater has ΔB/K <0). Both freshwater and marine waters and rocks are low in germanium compared with silicon, with a Ge/Si ratio <1 μmol/mol, but soils have an order of magnitude, or more Ge/Si. Freshwater has lower sulfur than carbon, and paleosalinity indices are C/S ratio (fresh has C/S > 9), or S/C ratio (fresh has S/C <0.1). Strontium is now more abundant than barium in the ocean than in freshwater but was less abundant in the Proterozoic (fresh was then Sr/Ba <0.08). The results of these various analyses for Ediacaran paleosols and fossils of South Australia demonstrate fully freshwater conditions, or soils, and limited local estuarine influence. Ediacaran vendobionts formed terrestrial assemblages distinct from marine stromatolites and worm tubes. Ediacaran paleosols supplied nutrient cations including phosphorus to fuel the Cambrian Explosion of life in the sea.