Date: 2013-01-31
Reference number: OPUSeJ 201301312334ELL
Links: published article http://www.ncbi.nlm.nih.gov/pubmed/23235827
Forum: http://www.opusej.org/library/ediacaran-life-on-land-forum/
Title: Ediacaran life on land
Author: Gregory J. Retallack
Abstract: Ediacaran (635-542 million years ago) fossils have been regarded as early animal ancestors of the Cambrian evolutionary explosion of marine invertebrate phyla, as giant marine protists and as lichenized fungi. Recent documentation of palaeosols in the Ediacara Member of the Rawnsley Quartzite of South Australia confirms past interpretations of lagoonal-aeolian deposition based on synsedimentary ferruginization and loessic texture. Further evidence for palaeosols comes from non-marine facies, dilation cracks, soil nodules, sand crystals, stable isotopic data and mass balance geochemistry. Here I show that the uppermost surfaces of the palaeosols have a variety of fossils in growth position, including Charniodiscus, Dickinsonia, Hallidaya, Parvancorina, Phyllozoon, Praecambridium, Rugoconites, Tribrachidium and ‘old-elephant skin’ (ichnogenus Rivularites). These fossils were preserved as ferruginous impressions, like plant fossils, and biological soil crusts of Phanerozoic eon sandy palaeosols. Sand crystals after gypsum and nodules of carbonate are shallow within the palaeosols, even after correcting for burial compaction. Periglacial involutions and modest geochemical differentiation of the palaeosols are evidence of a dry, cold temperate Ediacaran palaeoclimate in South Australia. This new interpretation of some Ediacaran fossils as large sessile organisms of cool, dry soils, is compatible with observations that Ediacaran fossils were similar in appearance and preservation to lichens and other microbial colonies of biological soil crusts, rather than marine animals, or protists.
Author bio: N/A
Sponsor editor: N/A
Affiliations/disclaimers/funding/acknowledgements: Department of Geological Sciences, University of Oregon, Eugene, Oregon 97403-1272, USA. The author declares no competing financial interests. K. Lloyd, P. Coulthard, A. Coulthard, K. Anderson and D. Crawford facilitated permission to undertake research in Flinders Ranges National Park. B. Logan and M. Willison aided sampling of drill core at PIRSA, Glenside. T. Palmer and D. Atkins provided mathematical advice. Fieldwork was funded by the PRF fund of the American Chemical Society, and aided by C. Metzger and J. Gehling.
Keywords: N/A
Subject: Science/ Ediacaran fossils
Language: English
Bibliography: (alphabetical) N/A
Citation: Retallack, G J, 2013, “Ediacaran life on land”, Nature 493, 89–92. Online 03 January 2013. doi:10.1038/nature11777 http://www.ncbi.nlm.nih.gov/pubmed/23235827
References: see Forum http://www.opusej.org/library/ediacaran-life-on-land-forum/