The nature of fossils from the Ediacaran period, some 635 million–542 million years ago, has been fiercely debated by palaeontologists. But where others envisage Ediacaran sea beds crawling with archaic animals, Gregory Retallack, a geologist at the University of Oregon in Eugene sees these sites in southern Australia as dry, terrestrial landscapes dotted with lichens. He proposes that rock in the Ediacara Member in South Australia — where palaeontologist Reginald Sprigg first discovered Ediacaran fossils in 1947 — represents ancient soils, and presents new geological data. Among other lines of evidence, Retallack argues that the rock’s red colour and weathering pattern indicate that the deposits were formed in terrestrial — not marine — environments (abstract). Others strongly disagree."
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