Modern iron isotope perspective on the benthic iron shuttle and the redox evolution of ancient oceans

Severmann, Silke; Lyons, Timothy W.; Anbar, Ariel D.; McManus, James; Gordon, Gwyneth W.

doi:10.1130/g24670a.1

Cited by 205 publications

(160 citation statements)

References 25 publications

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“…Shelf sediment porewaters supply dissolved iron into overlying seawater by diffusion across the sediment-water interface (McManus et al, 1997;Berelson et al, 2003;Elrod et al, 2004). The contribution of this mechanism to shuttle transport is supported by iron isotope measurements showing that isotopically light iron derived from the continental shelf may make a significant contribution to deep sea sediments (Severmann et al, 2009;Homoky et al, 2009 ). These data seem to suggest that fluxes lie in a narrow range that rarely exceeds 30 µg cm -2 year -1 that scarcely seems enough to provide the iron enrichment in euxinic sediments.…”

Section: Reactive Iron Sourced From Shelf Sediment Porewatersmentioning

confidence: 73%

“…Iron isotopes offer the possibility that porewater Fe derived from the shelf can be identified in deep basin sediments. Distinctively low δ 56 Fe values have been found in continental shelf source sediment (Severmann et al, 2009) that can be recorded in euxinic sediments (Lyons and Severmann, 2006;Duan et al, 2010). Further isotope studies should clarify the relative importance of eroded shelf sediments and porewater dissolved Fe in producing the distinctive enrichment signal in euxinic sediments.…”

Section: Insights From the Black Seamentioning

confidence: 99%

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The Iron Biogeochemical Cycle Past and Present

Raiswell¹,

Canfield²

2012

GeochemPersp

552

445

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Section: Reactive Iron Sourced From Shelf Sediment Porewatersmentioning

confidence: 73%

Section: Insights From the Black Seamentioning

confidence: 99%

The Iron Biogeochemical Cycle Past and Present

Raiswell¹,

Canfield²

2012

GeochemPersp

552

445

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“…Basin-wide transport of DIRgenerated dissolved Fe(II) has been referred to as a "benthic iron shuttle" (Anderson and Raiswell, 2004), and has been inferred to have occurred in Archaean and Proterozoic basins (Severmann et al, 2008).…”

Section: Continental Sources Of Iron To the Oceansmentioning

confidence: 99%

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

Konhauser

Planavsky

Hardisty

et al. 2017

Earth-Science Reviews

337

257

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“…Fe HR refers to Fe minerals that are considered highly reactive towards biological and abiological reduction under anoxic conditions (Canfield et al, 1992;Poulton et al, 2004b), and includes carbonate-associated Fe (Fe carb ; e.g., ankerite and siderite), ferric (oxyhydr)oxides (Fe ox ; e.g., goethite and hematite), magnetite Fe (Fe mag ) and Fe sulfide minerals (Fe py ; e.g., makinawite and pyrite) (Poulton and Canfield, 2005). Sediments may be enriched in Fe HR under anoxic marine conditions due to either the export of remobilized Fe (aq) from the oxic shelf (Anderson and Raiswell, 2004;Severmann et al, 2008) or under more widespread anoxia, due to upwelling of deep water Fe(II) (Poulton and Canfield, 2011).…”

Section: Fe-speciationmentioning

confidence: 99%

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

Wood

Poulton

Prave

et al. 2015

Precambrian Research

161

194

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A c c e p t e d M a n u s c r i p t 3 ABSTRACTThe first appearance of skeletal metazoans in the late Ediacaran (~550 million years ago; Ma) has been linked to the widespread development of oxygenated oceanic conditions, but a precise spatial and temporal reconstruction of their evolution has not been resolved. Here we consider the evolution of ocean chemistry from ~550 to ~541 Ma across shelf-to-basin transects in the Zaris and Witputs Sub-Basins of the Nama Group, Namibia. New carbon isotope data capture the final stages of the Shuram/Wonoka deep negative C-isotope excursion, and these are complemented with a reconstruction of water column redox dynamics utilizing Fe-S-C systematics and the distribution of skeletal and soft-bodied metazoans. Combined, these inter-basinal datasets provide insight into the potential role of ocean redox chemistry during this pivotal interval of major biological innovation.The strongly negative  13 C values in the lower parts of the sections reflect both a secular, global change in the C-isotopic composition of Ediacaran seawater, as well as the influence of 'local' basinal effects as shown by the most negative  13 C values occurring in the transition from distal to proximal ramp settings. Critical, though, is that the transition to positive  13 C values postdates the appearance of calcified metazoans, indicating that the onset of biomineralization did not occur under post-excursion conditions. Significantly, we find that anoxic and ferruginous deeper water column conditions were prevalent during and after the transition to positive  13 C that marks the end of the Shuram/Wonoka excursion. Thus, if the C isotope trend reflects the transition to global-scale oxygenation in the aftermath of the oxidation of a large-scale, isotopically light organic carbon pool, it was not sufficient to fully oxygenate the deep ocean. Page 4 of 74A c c e p t e d M a n u s c r i p t 4 Both sub-basins reveal highly dynamic redox structures, where shallow, inner ramp settings experienced transient oxygenation. Anoxic conditions were caused either by episodic upwelling of deeper anoxic waters or higher rates of productivity. These settings supported short-lived and monospecific skeletal metazoan communities. By contrast, microbial (thrombolite) reefs, found in deeper inner-and mid-ramp settings, supported more biodiverse communities with complex ecologies and large skeletal metazoans. These long-lived reef communities, as well as Ediacaran soft-bodied biotas, are found particularly within transgressive systems, where oxygenation was persistent. We suggest that a mid-ramp position enabled physical ventilation mechanisms for shallow water column oxygenation to operate during flooding and transgressive sea-level rise. Our data support a prominent role for oxygen, and for stable oxygenated conditions in particular, in controlling both the distribution and ecology of Ediacaran skeletal metazoan communities.Keywords: Oxygenation; Neoproterozoic; Biomineralisation; Metazoans; Ediacaran; Ecosystems Introductio...

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Modern iron isotope perspective on the benthic iron shuttle and the redox evolution of ancient oceans

Cited by 205 publications

References 25 publications

The Iron Biogeochemical Cycle Past and Present

The Iron Biogeochemical Cycle Past and Present

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

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

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