Geobiology最新文献

{"title":"Biogeochemical transformations after the emergence of oxygenic photosynthesis and conditions for the first rise of atmospheric oxygen","authors":"Yasuto Watanabe,&nbsp;Eiichi Tajika,&nbsp;Kazumi Ozaki","doi":"10.1111/gbi.12554","DOIUrl":"https://doi.org/10.1111/gbi.12554","url":null,"abstract":"<p>The advent of oxygenic photosynthesis represents the most prominent biological innovation in the evolutionary history of the Earth. The exact timing of the evolution of oxygenic photoautotrophic bacteria remains elusive, yet these bacteria profoundly altered the redox state of the ocean–atmosphere–biosphere system, ultimately causing the first major rise in atmospheric oxygen (O₂)—the so-called Great Oxidation Event (GOE)—during the Paleoproterozoic (~2.5–2.2 Ga). However, it remains unclear how the coupled atmosphere–marine biosphere system behaved after the emergence of oxygenic photoautotrophs (OP), affected global biogeochemical cycles, and led to the GOE. Here, we employ a coupled atmospheric photochemistry and marine microbial ecosystem model to comprehensively explore the intimate links between the atmosphere and marine biosphere driven by the expansion of OP, and the biogeochemical conditions of the GOE. When the primary productivity of OP sufficiently increases in the ocean, OP suppresses the activity of the anaerobic microbial ecosystem by reducing the availability of electron donors (H₂ and CO) in the biosphere and causes climate cooling by reducing the level of atmospheric methane (CH₄). This can be attributed to the supply of OH radicals from biogenic O₂, which is a primary sink of biogenic CH₄ and electron donors in the atmosphere. Our typical result also demonstrates that the GOE is triggered when the net primary production of OP exceeds &gt;~5% of the present oceanic value. A globally frozen snowball Earth event could be triggered if the atmospheric CO₂ level was sufficiently small (&lt;~40 present atmospheric level; PAL) because the concentration of CH₄ in the atmosphere would decrease faster than the climate mitigation by the carbonate–silicate geochemical cycle. These results support a prolonged anoxic atmosphere after the emergence of OP during the Archean and the occurrence of the GOE and snowball Earth event during the Paleoproterozoic.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 5","pages":"537-555"},"PeriodicalIF":3.7,"publicationDate":"2023-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5782382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralogical characterization of biosilicas versus geological analogs","authors":"Gabriela A. Farfan,&nbsp;David A. McKeown,&nbsp;Jeffrey E. Post","doi":"10.1111/gbi.12553","DOIUrl":"https://doi.org/10.1111/gbi.12553","url":null,"abstract":"<p>Non-crystalline silica mineraloids are essential to life on Earth as they provide architectural structure to dominant primary producers, such as plants and phytoplankton, as well as to protists and sponges. Due to the difficulty in characterizing and quantifying the structure of highly disordered X-ray amorphous silica, relatively little has been done to understand the mineralogy of biogenic silica and how this may impact the material properties of biogenic silica, such as hardness and strength, or how biosilica might be identified and differentiated from its inorganic geological counterparts. Typically, geologically formed opal-A and hyalite opal-A_N are regarded as analogs to biogenic silica, however, some spectroscopic and imaging studies suggest that this might not be a reasonable assumption. In this study, we use a variety of techniques (X-ray diffraction, Raman spectroscopy, and scanning electron microscopy) to compare differences in structural disorder and bonding environments of geologically formed hydrous silicas (Opal-A, hyalite, geyserite) and silica glass versus biogenic silicas from an array of organisms. Our results indicate differences in the levels of structural disorder and the Raman-observed bonding environments of the SiO₂ network modes (D₁ mode) and the Q-species modes (~1015 cm⁻¹) between varieties of biogenic silicas and geologically formed silicas, which aligns with previous studies that suggest fundamental differences between biogenic and geologically formed silica. Biosilicas also differ structurally from one another by species of organism. Our mineralogical approach to characterizing biosilicas and differentiating them from other silicas may be expanded to future diagenesis studies, and potentially applied to astrobiology studies of Earth and other planets.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 4","pages":"520-533"},"PeriodicalIF":3.7,"publicationDate":"2023-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12553","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5876231","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ediacaran–Cambrian bioturbation did not extensively oxygenate sediments in shallow marine ecosystems","authors":"Alison T. Cribb,&nbsp;Sebastiaan J. van de Velde,&nbsp;William M. Berelson,&nbsp;David J. Bottjer,&nbsp;Frank A. Corsetti","doi":"10.1111/gbi.12550","DOIUrl":"https://doi.org/10.1111/gbi.12550","url":null,"abstract":"<p>The radiation of bioturbation during the Ediacaran–Cambrian transition has long been hypothesized to have oxygenated sediments, triggering an expansion of the habitable benthic zone and promoting increased infaunal tiering in early Paleozoic benthic communities. However, the effects of bioturbation on sediment oxygen are underexplored with respect to the importance of biomixing and bioirrigation, two bioturbation processes which can have opposite effects on sediment redox chemistry. We categorized trace fossils from the Ediacaran and Terreneuvian as biomixing or bioirrigation fossils and integrated sedimentological proxies for bioturbation intensity with biogeochemical modeling to simulate oxygen penetration depths through the Ediacaran–Cambrian transition. Ultimately, we find that despite dramatic increases in ichnodiversity in the Terreneuvian, biomixing remains the dominant bioturbation behavior, and in contrast to traditional assumptions, Ediacaran–Cambrian bioturbation was unlikely to have resulted in extensive oxygenation of shallow marine sediments globally.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 4","pages":"435-453"},"PeriodicalIF":3.7,"publicationDate":"2023-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12550","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5982731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A carbonate corrosion experiment at a marine methane seep: The role of aerobic methanotrophic bacteria","authors":"Alexmar Cordova-Gonzalez,&nbsp;Daniel Birgel,&nbsp;Max Wisshak,&nbsp;Tim Urich,&nbsp;Florian Brinkmann,&nbsp;Yann Marcon,&nbsp;Gerhard Bohrmann,&nbsp;J?rn Peckmann","doi":"10.1111/gbi.12549","DOIUrl":"https://doi.org/10.1111/gbi.12549","url":null,"abstract":"Methane seeps are typified by the formation of authigenic carbonates, many of which exhibit corrosion surfaces and secondary porosity believed to be caused by microbial carbonate dissolution. Aerobic methane oxidation and sulfur oxidation are two processes capable of inducing carbonate corrosion at methane seeps. Although the potential of aerobic methanotrophy to dissolve carbonate was confirmed in laboratory experiments, this process has not been studied in the environment to date. Here, we report on a carbonate corrosion experiment carried out in the REGAB Pockmark, Gabon‐Congo‐Angola passive margin, in which marble cubes were deployed for 2.5 years at two sites (CAB‐B and CAB‐C) with apparent active methane seepage and one site (CAB‐D) without methane seepage. Marble cubes exposed to active seepage (experiment CAB‐C) were found to be affected by a new type of microbioerosion. Based on 16S rRNA gene analysis, the biofilms adhering to the bioeroded marble mostly consisted of aerobic methanotrophic bacteria, predominantly belonging to the uncultured Hyd24‐01 clade. The presence of abundant 13C‐depleted lipid biomarkers including fatty acids (n‐C16:1ω8c, n‐C18:1ω8c, n‐C16:1ω5t), various 4‐mono‐ and 4,4‐dimethyl sterols, and diplopterol agrees with the dominance of aerobic methanotrophs in the CAB‐C biofilms. Among the lipids of aerobic methanotrophs, the uncommon 4α‐methylcholest‐8(14)‐en‐3β,25‐diol is interpreted to be a specific biomarker for the Hyd24‐01 clade. The combination of textural, genetic, and organic geochemical evidence suggests that aerobic methanotrophs are the main drivers of carbonate dissolution observed in the CAB‐C experiment at the REGAB pockmark.","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 4","pages":"491-506"},"PeriodicalIF":3.7,"publicationDate":"2023-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12549","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6193380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Astronomically controlled deep-sea life in the Late Cretaceous reconstructed from ultra-high-resolution inoceramid shell archives","authors":"Adam Wierzbicki,&nbsp;Erik Wolfgring,&nbsp;Michael Wagreich,&nbsp;Mariusz K?dzierski,&nbsp;Regina Mertz-Kraus","doi":"10.1111/gbi.12548","DOIUrl":"https://doi.org/10.1111/gbi.12548","url":null,"abstract":"<p>The periodicity of the mutual position of celestial bodies in the Earth-Moon-Sun system is crucial to the functioning of life on Earth. Biological rhythms affect most of the processes inside organisms, and some can be recorded in skeletal remains, allowing one to reconstruct the cycles that occur in nature deep in time. In the present study, we have used ultra-high-resolution elemental ratio scans of Mg/Ca, Sr/Ca and Mn/Ca from the fossil, ca. 70 Ma old inoceramid bivalve <i>Inoceramus</i> (<i>Platyceramus</i>) <i>salisburgensis</i> from deep aphotic water and identified a clear regularity of repetition of the geochemical signal every of ~0.006 mm. We estimate that the shell accretion rate is on average ~0.4 cm of shell thickness per lunar year. Visible light–dark lamination, interpreted as a seasonal signal corresponding to the semilunar-related cycle, gives a rough shell age estimate and growth rate for this large bivalve species supported by a dual feeding strategy. We recognize a biological clock that follows either a semilunar (model A) or a tidal (model B) cycle. This cycle of tidal dominance seems to fit better considering the biological behaviour of <i>I</i>. (<i>P</i>.) <i>salisburgensis</i>, including the estimated age and growth rate of the studied specimens. We interpret that the major control in such deep-sea environment, well below the photic zone and storm wave base, was due to barotropic tidal forces, thus changing the water pressure.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 4","pages":"474-490"},"PeriodicalIF":3.7,"publicationDate":"2023-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12548","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6165802","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Revisiting marine redox conditions during the Ediacaran Shuram carbon isotope excursion","authors":"Zheng Gong,&nbsp;Guang-Yi Wei,&nbsp;Mojtaba Fakhraee,&nbsp;Lewis J. Alcott,&nbsp;Lei Jiang,&nbsp;Mingyu Zhao,&nbsp;Noah J. Planavsky","doi":"10.1111/gbi.12547","DOIUrl":"https://doi.org/10.1111/gbi.12547","url":null,"abstract":"<p>The Neoproterozoic carbonate record contains multiple carbon isotope anomalies, which are the subject of intense debate. The largest of these anomalies, the Shuram excursion (SE), occurred in the mid-Ediacaran (~574–567 Ma). Accurately reconstructing marine redox landscape is a clear path toward making sense of the mechanism that drives this δ¹³C anomaly. Here, we report new uranium isotopic data from the shallow-marine carbonates of the Wonoka Formation, Flinders Ranges, South Australia, where the SE is well preserved. Our data indicate that the δ²³⁸U trend during the SE is highly reproducible across globally disparate sections from different depositional settings. Previously, it was proposed that the positive shift of δ²³⁸U values during the SE suggests an extensive, near-modern level of marine oxygenation. However, recent publications suggest that the fractionation of uranium isotopes in ferruginous and anoxic conditions is comparable, opening up the possibility of non-unique interpretations of the carbonate uranium isotopic record. Here, we build on this idea by investigating the SE in conjunction with additional geochemical proxies. Using a revised uranium isotope mass balance model and an inverse stochastic carbon cycle model, we reevaluate models for δ¹³C and δ²³⁸U trends during the SE. We suggest that global seawater δ²³⁸U values during the SE could be explained by an expansion of ferruginous conditions and do not require a near-modern level of oxygenation during the mid-Ediacaran.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 4","pages":"407-420"},"PeriodicalIF":3.7,"publicationDate":"2023-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6130307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Protracted oxygenation across the Cambrian–Ordovician transition: A key initiator of the Great Ordovician Biodiversification Event?","authors":"Nevin P. Kozik,&nbsp;Seth A. Young,&nbsp;Anders Lindskog,&nbsp;Per Ahlberg,&nbsp;Jeremy D. Owens","doi":"10.1111/gbi.12545","DOIUrl":"https://doi.org/10.1111/gbi.12545","url":null,"abstract":"<p>Fluctuations in marine oxygen concentrations have been invoked as a primary driver for changes in biodiversity throughout Earth history. Expansions in reducing marine conditions are commonly invoked as key causal mechanisms for mass extinctions, while increases in marine oxygenation are becoming an increasingly common causal mechanism invoked for biodiversification events. Here we utilize a multiproxy approach to constrain local and global marine paleoredox conditions throughout the late Cambrian–Early Ordovician from two drill core successions in Baltoscandia. Local paleoredox proxies such as manganese concentrations and iron speciation reveal that both sites in the Baltic paleobasin had persistently anoxic and predominantly euxinic (anoxic and sulfidic) bottom water conditions throughout the study interval. Corresponding trace metal datasets indicate nuanced contraction and expansion of global anoxic and euxinic conditions along continental margins during the late Cambrian–Early Ordovician. Lastly, thallium isotope data from these locally reducing sections suggest a global expansion of oxygenated shelf and deeper marine environments from the late Cambrian into the Early Ordovician. This evidence for increasingly oxic marine environments coincides with increases in burrowing depth and tiering in marine animals, as well as diversification of body fossils throughout this ~8-million-year interval. The collective geochemical datasets provide some of the first direct paleoredox evidence for an increase in marine oxygen concentrations as a key mechanism for the Ordovician radiation of marine life.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 3","pages":"323-340"},"PeriodicalIF":3.7,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5816619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Organic preservation of vase-shaped microfossils from the late Tonian Chuar Group, Grand Canyon, Arizona, USA","authors":"Kelly E. Tingle,&nbsp;Susannah M. Porter,&nbsp;Morgan R. Raven,&nbsp;Andrew D. Czaja,&nbsp;Samuel M. Webb,&nbsp;Bonnie Bloeser","doi":"10.1111/gbi.12544","DOIUrl":"https://doi.org/10.1111/gbi.12544","url":null,"abstract":"<p>Vase-shaped microfossils (VSMs) are found globally in middle Neoproterozoic (800–730 Ma) marine strata and represent the earliest evidence for testate (shell-forming) amoebozoans. VSM tests are hypothesized to have been originally organic in life but are most commonly preserved as secondary mineralized casts and molds. A few reports, however, suggest possible organic preservation. Here, we test the hypothesis that VSMs from shales of the lower Walcott Member of the Chuar Group, Grand Canyon, Arizona, contain original organic material, as reported by B. Bloeser in her pioneering studies of Chuar VSMs. We identified VSMs from two thin section samples of Walcott Member black shales in transmitted light microscopy and used scanning electron microscopy to image VSMs. Carbonaceous material is found within the internal cavity of all VSM tests from both samples and is interpreted as bitumen mobilized from Walcott shales likely during the Cretaceous. Energy dispersive X-ray spectroscopy (EDS) and wavelength dispersive X-ray spectroscopy (WDS) reveal that VSM test walls contain mostly carbon, iron, and sulfur, while silica is present only in the surrounding matrix. Raman spectroscopy was used to compare the thermal maturity of carbonaceous material within the samples and indicated the presence of pyrite and jarosite within fossil material. X-ray absorption spectroscopy revealed the presence of reduced organic sulfur species within the carbonaceous test walls, the carbonaceous material found within test cavities, and in the sedimentary matrix, suggesting that organic matter sulfurization occurred within the Walcott shales. Our suite of spectroscopic analyses reveals that Walcott VSM test walls are organic and sometimes secondarily pyritized (with the pyrite variably oxidized to jarosite). Both preservation modes can occur at a millimeter spatial scale within sample material, and at times even within a single specimen. We propose that sulfurization within the Walcott Shales promoted organic preservation, and furthermore, the ratio of iron to labile VSM organic material controlled the extent of pyrite replacement. Based on our evidence, we conclude that the VSMs are preserved with original organic test material, and speculate that organic VSMs may often go unrecognized, given their light-colored, translucent appearance in transmitted light.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 3","pages":"290-309"},"PeriodicalIF":3.7,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12544","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"5744747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Iron-mediated anaerobic ammonium oxidation recorded in the early Archean ferruginous ocean","authors":"Alice Pellerin,&nbsp;Christophe Thomazo,&nbsp;Magali Ader,&nbsp;Johanna Marin-Carbonne,&nbsp;Julien Alleon,&nbsp;Emmanuelle Vennin,&nbsp;Axel Hofmann","doi":"10.1111/gbi.12540","DOIUrl":"https://doi.org/10.1111/gbi.12540","url":null,"abstract":"<p>The nitrogen isotopic composition of organic matter is controlled by metabolic activity and redox speciation and has therefore largely been used to uncover the early evolution of life and ocean oxygenation. Specifically, positive δ¹⁵N values found in well-preserved sedimentary rocks are often interpreted as reflecting the stability of a nitrate pool sustained by water column partial oxygenation. This study adds much-needed data to the sparse Paleoarchean record, providing carbon and nitrogen concentrations and isotopic compositions for more than fifty samples from the 3.4 Ga Buck Reef Chert sedimentary deposit (BRC, Barberton Greenstone Belt). In the overall anoxic and ferruginous conditions of the BRC depositional environment, these samples yield positive δ¹⁵N values up to +6.1‰. We argue that without a stable pool of nitrates, these values are best explained by non-quantitative oxidation of ammonium via the Feammox pathway, a metabolic co-cycling between iron and nitrogen through the oxidation of ammonium in the presence of iron oxides. Our data contribute to the understanding of how the nitrogen cycle operated under reducing, anoxic, and ferruginous conditions, which are relevant to most of the Archean. Most importantly, they invite to carefully consider the meaning of positive δ¹⁵N signatures in Archean sediments.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 3","pages":"277-289"},"PeriodicalIF":3.7,"publicationDate":"2023-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/gbi.12540","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6211434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple sulphur isotope record of Paleoarchean sedimentary rocks across the Onverwacht Group, Barberton Greenstone Belt, South Africa","authors":"Eugene G. Grosch,&nbsp;Nicola McLoughlin,&nbsp;Martin Whitehouse","doi":"10.1111/gbi.12542","DOIUrl":"https://doi.org/10.1111/gbi.12542","url":null,"abstract":"<p>This study presents multiple sulphur isotope (³²S, ³³S, ³⁴S, ³⁶S) data on pyrites from silicified volcano-sedimentary rocks of the Paleoarchean Onverwacht Group of the Barberton greenstone belt, South Africa. These rocks include seafloor cherts and felsic conglomerates that were deposited in shallow marine environments preserving a record of atmospheric and biogeochemical conditions on the early Earth. A strong variation in mass independent sulphur isotope fractionation (MIF-S) anomalies is found in the cherts, with Δ³³S ranging between −0.26‰ and 3.42‰. We explore possible depositional and preservational factors that could explain some of this variation seen in MIF-S. Evidence for microbial activity is recorded by the c. 3.45 Ga Hooggenoeg Formation Chert (HC4) preserving a contribution of microbial sulphate reduction (−Δ³³S and –δ³⁴S), and a c. 3.33 Ga Kromberg Formation Chert (KC5) recording a possible contribution of microbial elemental sulphur disproportionation (+Δ³³S and –δ³⁴S). Pyrites from a rhyo-dacitic conglomerate of the Noisy Formation do not plot along a previously proposed global Felsic Volcanic Array, and this excludes short-lived pulses of intense felsic volcanic gas emissions as the dominant control on Archean MIF-S. Rather, we suggest that the MIF-S signals measured reflect dilution during marine deposition, early diagenetic modification, and mixing with volcanic/hydrothermal S sources. Given the expanded stratigraphic interval (3.47–3.22 Ga) now sampled from across the Barberton Supergroup, we conclude that large MIF-S exceeding &gt;4‰ is atypical of Paleoarchean near-surface environments on the Kaapvaal Craton.</p>","PeriodicalId":173,"journal":{"name":"Geobiology","volume":"21 2","pages":"153-167"},"PeriodicalIF":3.7,"publicationDate":"2022-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"6050684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}