Oxidation of the Ediacaran Ocean

Abstract

Oxygenation of the Earth's surface is increasingly thought to have occurred in two steps. The first step, which occurred approximately 2,300 million years (Myr) ago, involved a significant increase in atmospheric oxygen concentrations and oxygenation of the surface ocean. A further increase in atmospheric oxygen appears to have taken place during the late Neoproterozoic period ( approximately 800-542 Myr ago). This increase may have stimulated the evolution of macroscopic multicellular animals and the subsequent radiation of calcified invertebrates, and may have led to oxygenation of the deep ocean. However, the nature and timing of Neoproterozoic oxidation remain uncertain. Here we present high-resolution carbon isotope and sulphur isotope records from the Huqf Supergroup, Sultanate of Oman, that cover most of the Ediacaran period (approximately 635 to approximately 548 Myr ago). These records indicate that the ocean became increasingly oxygenated after the end of the Marinoan glaciation, and they allow us to identify three distinct stages of oxidation. When considered in the context of other records from this period, our data indicate that certain groups of eukaryotic organisms appeared and diversified during the second and third stages of oxygenation. The second stage corresponds with the Shuram excursion in the carbon isotope record and seems to have involved the oxidation of a large reservoir of organic carbon suspended in the deep ocean, indicating that this event may have had a key role in the evolution of eukaryotic organisms. Our data thus provide new insights into the oxygenation of the Ediacaran ocean and the stepwise restructuring of the carbon and sulphur cycles that occurred during this significant period of Earth's history.

Dynamic redox conditions control late Ediacaran metazoan ecosystems in the Nama Group, Namibia

“…This has variously been interpreted as being due to oxidation of a substantial reservoir of organic carbon dissolved in the deep ocean (Rothman et al, 2003;Fike et al, 2006), to a large flux of methane released from clathrates (Bjerrum and Canfield, 2011), or to diagenetic phenomena (Derry, 2010). The models of Bristow and Kennedy (2008), however, suggest that there were not enough oxidants available for the model proposed by Fike et al (2006), and thus that the Shuram could not have represented a large scale oxidation event.Indeed, the global response of ocean redox chemistry to rising oxygen levels through this period has been shown to be complex (Fike et al, 2006;Canfield et al, 2008;Johnston et al, 2010Johnston et al, , 2012bSperling et al, 2013a) A c c e p t e d M a n u s c r i p t 6 state existed until at least ~580 Ma, and beyond in certain areas (Canfield et al, 2008;Planavsky et al, 2011;Poulton and Canfield, 2011), whereas surface-water oxygenation is thought to be a near-continuous feature throughout the latter half of the Ediacaran (Canfield et al, 2008). Indeed some have argued that pervasive and persistent oxygenation of the deep ocean did not occur until the later Palaeozoic (e.g.…”

“…Embryos of possible metazoans are known from at least ~600-580 Ma (Xiao et al, 1998), while the first unequivocal calcified metazoans were present by ~550 Ma (Germs, 1972). The subsequent rapid diversification of metazoans with hard parts around the Precambrian-Cambrian boundary (541 Ma) marks a step change in biodiversity, the complexity of marine ecosystems, and in the workings of the global carbon cycle.Metazoans demand oxygen to support aerobic metabolisms and skeletal hard-parts, and so it has been presumed that a rise in oxygen, perhaps incrementally, facilitated the evolution of this complexity (Fike et al, 2006;Canfield et al, 2007Canfield et al, , 2008 McFadden et al, 2008; Scott et al., 2008).Chemical tracers reveal a profound change in major biogeochemical cycles during the Ediacaran, such as the global Shuram/Wonoka deep negative C-isotope excursion (Burns and Matter, 1993). This has variously been interpreted as being due to oxidation of a substantial reservoir of organic carbon dissolved in the deep ocean (Rothman et al, 2003;Fike et al, 2006), to a large flux of methane released from clathrates (Bjerrum and Canfield, 2011), or to diagenetic phenomena (Derry, 2010).…”

Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

“…Numerous geochemical data have been obtained to reconstruct changes in the marine environment during that time. Some geochemical studies suggest that ocean basins were well oxygenated by the late Ediacaran (Canfield et al, 2007;Fike et al, 2006;Scott et al, 2008). However, more researchers provide evidence for the persistence of ferruginous and/or intermittently euxinic deep waters into the early Cambrian, particularly over the Yangtze block of South China (Canfield et al, 2008;Goldberg et al, 2007;Li et al, 2010;Och et al, 2013;Poulton and Canfield, 2011;Wille et al, 2008;Xu et al, 2012).…”

New records of late Ediacaran microbiota from Poland

“…Shallow marine ecosystems, which have the best fossil record, have been affected by processes related to plate tectonics, transgressive and regressive cycles, weathering of continents, hydrosphere chemistry and oxygen content, hydrological cycle, and climatic fluctuations Fike et al, 2006;Canfield et al, 2007). The biodiversity was increasing through time, albeit with periodic retardations, because of evolutionary innovations and the appearance of new clades of unicellular and metaphytic * Tel.…”