Texture-specific Si isotope variations in Barberton Greenstone Belt cherts record low temperature fractionations in early Archean seawater

Stefurak, E. J.; Fischer, Woodward W.; Lowe, Donald R.

doi:10.1016/j.gca.2014.11.014

Cited by 53 publications

(42 citation statements)

References 96 publications

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“…Alternatively, these signals could largely be the result of alteration of sedimentary strata by postdepositional fluids. While chemical imaging approaches exist for evaluating the impacts of post-depositional alteration (e.g., Johnson et al 2013a;Fischer et al 2014;Stefurak et al 2015), a critical issue going forward will be constructing analytical frameworks that are able to carefully consider and avoid false positive detections of oxygenic Cyanobacteria in the early sedimentary record, particularly as geochemical techniques for O 2 detection continue to become more sophisticated and more sensitive.…”

Section: Discussionmentioning

confidence: 99%

Timescales of Oxygenation Following the Evolution of Oxygenic Photosynthesis

Ward

Kirschvink

Fischer

2015

Orig Life Evol Biosph

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Among the most important bioenergetic innovations in the history of life was the invention of oxygenic photosynthesis-autotrophic growth by splitting water with sunlight-by Cyanobacteria. It is widely accepted that the invention of oxygenic photosynthesis ultimately resulted in the rise of oxygen by ca. 2.35 Gya, but it is debated whether this occurred more or less immediately as a proximal result of the evolution of oxygenic Cyanobacteria or whether they originated several hundred million to more than one billion years earlier in Earth history. The latter hypothesis involves a prolonged period during which oxygen production rates were insufficient to oxidize the atmosphere, potentially due to redox buffering by reduced species such as higher concentrations of ferrous iron in seawater. To examine the characteristic timescales for environmental oxygenation following the evolution of oxygenic photosynthesis, we applied a simple mathematical approach that captures many of the salient features of the major biogeochemical fluxes and reservoirs present in Archean and early Paleoproterozoic surface environments. Calculations illustrate that oxygenation would have overwhelmed redox buffers within ~100 kyr following the emergence of oxygenic photosynthesis, a geologically short amount of time unless rates of primary production were far lower than commonly expected. Fundamentally, this result arises because of the multiscale nature of the carbon and oxygen cycles: rates of gross primary production are orders of magnitude too fast for oxygen to be masked by Earth's geological buffers, and can only be effectively matched by respiration at non-negligible O2 concentrations. These results suggest that oxygenic photosynthesis arose shortly before the rise of oxygen, not hundreds of millions of years before it.

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Section: Discussionmentioning

confidence: 99%

Timescales of Oxygenation Following the Evolution of Oxygenic Photosynthesis

Ward

Kirschvink

Fischer

2015

Orig Life Evol Biosph

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“…Frontiers in Marine Science | www.frontiersin.org Robert and Chaussidon (2006), van den Boorn et al (2007van den Boorn et al ( , 2010, Steinhoefel et al (2009Steinhoefel et al ( , 2010, Abraham et al (2011), Heck et al (2011), Chakrabarti et al (2012, Delvigne (2012), Marin-Carbonne et al (2014), Hu et al (2013), Ramseyer et al (2013), Geilert et al (2014), Li et al (2014), Brengman (2015, Stefurak et al (2015), Delvigne et al (2012), Wen et al (2016), and Ding et al (2017).…”

Section: Changing Si Biogeochemistry In the Precambrian Oceansmentioning

confidence: 99%

Biosilicification Drives a Decline of Dissolved Si in the Oceans through Geologic Time

et al. 2017

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Biosilicification has driven variation in the global Si cycle over geologic time. The evolution of different eukaryotic lineages that convert dissolved Si (DSi) into mineralized structures (higher plants, siliceous sponges, radiolarians, and diatoms) has driven a secular decrease in DSi in the global ocean leading to the low DSi concentrations seen today. Recent studies, however, have questioned the timing previously proposed for the DSi decreases and the concentration changes through deep time, which would have major implications for the cycling of carbon and other key nutrients in the ocean. Here, we combine relevant genomic data with geological data and present new hypotheses regarding the impact of the evolution of biosilicifying organisms on the DSi inventory of the oceans throughout deep time. Although there is no fossil evidence for true silica biomineralization until the late Precambrian, the timing of the evolution of silica transporter genes suggests that bacterial silicon-related metabolism has been present in the oceans since the Archean with eukaryotic silicon metabolism already occurring in the Neoproterozoic. We hypothesize that biological processes have influenced oceanic DSi concentrations since the beginning of oxygenic photosynthesis.

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“…Si isotopes are fractionated by many lowtemperature precipitation processes and can be useful in differentiating different generations of silica and in tracking the cycling of silica (Chakrabarti et al, 2012;Heck et al, 2011;Marin-Carbonne et al, 2012;Stefurak et al, 2015;van den Boorn et al, 2007van den Boorn et al, , 2010. The Si isotopic compositions of silica granules measured in this study had a mean δ 30 Si of -0.28‰ and standard deviation of 1.42‰ (n = 338), although analysis of variance (ANOVA) and multiple comparison tests indicated that sample means of granules associated with banded black-and-white chert, banded iron formation, and ferruginous chert were signifi cantly different ( Fig.…”

Section: Si Isotope Geochemistrymentioning

confidence: 99%

“…Although the volume of continental crust during Archean time was much less than on modern Earth Dhuime et al, 2012), Archean oceans had abundant silica sources in the form of weathering and alteration of mafi c and ultramafi c rocks (Siever, 1992); mass balance requires that abundant sinks must also have been present. Previous authors have suggested that banded iron formations, diagenetic silicifi cation, and authigenic clay precipitation (Maliva, 2001;Maliva et al, 1989Maliva et al, , 2005Siever, 1992;Stefurak et al, 2015) were important sinks in the Archean silica cycle. It has also long been suggested that primary chemical precipitation of amorphous silica phases also played a major role as a silica sink during Precambrian time (Lowe, 1999a;Maliva et al, 2005;Siever, 1992), which is supported by the abundance of chert, especially in pre-3.0 Ga Archean sequences.…”

Section: Introductionmentioning

confidence: 99%

Sedimentology and geochemistry of Archean silica granules

Stefurak

Lowe

Zentner

et al. 2015

Geological Society of America Bulletin

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The production of biogenic silica has dominated the marine silica cycle since early Paleozoic time, drawing down the concentration of dissolved silica in modern seawater to a few parts per million (ppm). Prior to the biological innovation of the fi rst silica biomineralizing organisms in late Proterozoic time, inputs of silica into Precambrian seawater were balanced by strictly chemical silica and silicate precipitation processes, although the mechanics of this abiotic marine silica cycle remain poorly understood. Cherty sedimentary rocks are abundant in Archean sequences, and many previous authors have suggested that primary precipitation of amorphous silica could have occurred in Archean seawater. The recent discovery that many pure chert layers in early Archean rocks formed as sedimentary beds of sandsized, subspherical silica granules has provided direct evidence for primary silica deposition. Here, we provide further sedimentological and geochemical analyses of early Archean silica granules in order to gain a better understanding of the mechanisms of granule formation. Silica granules are common components of sedimentary cherts from a variety of depositional settings and water depths. The abundance and widespread distribution of silica granules in Archean rocks suggest that they represented a signifi cant primary silica depositional mode and that most formed by precipitation in the upper part of the water column. The regular occurrence of silica granules as centimeterscale layers within banded chert alternating with layers of black or ferruginous chert containing few granules indicates episodic granule sedimentation. Contrasting silicon iso topic compositions of granules from different depo sitional environments indicate that isotopic signatures were modifi ed during early diagenesis. Looking to modern siliceous sinters for insight into silica precipitation, we suggest that silica granules may have formed via multiple stages of aggregation of silica nanospheres and microspheres. Consistent with this hypothesis, Archean ocean chemistry would have favored particle aggregation over gelling. Granule formation would have been most favorable under conditions promoting rapid silica polymerization, including high salinity and/or high concentrations of dissolved silica. Our observations suggest that granule sedimentation was often episodic, suggesting that granule formation may have also been episodic, perhaps linked to variations in these key parameters.

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Texture-specific Si isotope variations in Barberton Greenstone Belt cherts record low temperature fractionations in early Archean seawater

Cited by 53 publications

References 96 publications

Timescales of Oxygenation Following the Evolution of Oxygenic Photosynthesis

Timescales of Oxygenation Following the Evolution of Oxygenic Photosynthesis

Biosilicification Drives a Decline of Dissolved Si in the Oceans through Geologic Time

Sedimentology and geochemistry of Archean silica granules

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