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Carla M Koretsky - One of the best experts on this subject based on the ideXlab platform.
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The influence of road salt on seasonal mixing, Redox Stratification and methane concentrations in urban kettle lakes.
The Science of the total environment, 2019Co-Authors: Danielle Dupuis, Emily Sprague, Kathryn M. Docherty, Carla M KoretskyAbstract:Abstract Influxes of saline water from roads treated with deicers can alter the density structure of urban lakes. This can diminish or halt turnover events, such that lakes may transition from dimixis to monomixis or meromixis. In nutrient-rich lakes, this lack of turnover can produce persistent hypolimnetic anoxia. We hypothesized that diminished turnover in urban lakes impacted by road salt inputs would lead to increased accumulation of methane in the hypolimnia, with the potential for greater release of methane to the atmosphere via ebullition and from larger storage fluxes of methane when turnover events do occur. The lake water columns of two urban lakes (Woods Lake and Asylum Lake), previously suggested to have transitioned to meromixis and monomixis because of road salt deicer inputs, were sampled monthly from March 2016 to June 2017. A nearby rural lake (North Lake) less likely to be impacted by road salt and maintaining seasonal mixing, was also sampled for comparison. Lake column water was analyzed for conductivity, temperature, dissolved oxygen, ferrous iron, manganese, sulfide, calcium, magnesium, sodium, chloride and methane concentrations as a function of depth. All three lakes are eutrophic with at least seasonally anoxic hypolimnia. Our data are consistent with prior studies suggesting that Woods Lake has transitioned to meromixis and Asylum Lake to monomixis due to an influx of dense saline water from roads treated with deicers. In contrast, rural North Lake, which had much lower chloride, sodium and conductivity levels, was dimictic. The diminished or absent turnover in the two urban lakes during fall and spring resulted in persistently anoxic, Redox-stratified hypolimnia, with much larger accumulations of methane compared to the rural lake. This study demonstrates that road salt deicers impact lake mixing and biogeochemistry, especially methane concentrations, with the potential for significant increases in greenhouse gas emissions from urban lakes.
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Redox Stratification and Salinization of Three Kettle Lakes in Southwest Michigan, USA
Water Air & Soil Pollution, 2012Co-Authors: Carla M Koretsky, Andrew Macleod, Ryan J. Sibert, Christine SnyderAbstract:Redox Stratification, especially hypolimnetic anoxia resulting from eutrophication, and salinization resulting from application of salts for road deicing is investigated in three kettle lakes in southwest Michigan. Two of the lakes (Asylum and Woods Lakes) are located in urban Kalamazoo, Michigan, and the third (Brewster Lake) is located in rural Hastings, Michigan. In summer, the water columns of all three lakes are distinctly Redox stratified, with anoxic hypolimnia and significant accumulation of reduced solutes (e.g., Mn(II), Fe(II), ammonia) in the lake bottom waters. Extremely elevated conductivity, chloride, sodium, and potassium levels are observed in the urban Asylum and Woods Lakes compared to the rural Brewster Lake, presumably due to runoff of road salt deicers applied in the surrounding watershed. These significant changes in water quality are of concern because they may detrimentally impact lake mixing, biodiversity, and ecosystem function in the urban lakes.
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influence of spartina and juncus on saltmarsh sediments i pore water geochemistry
Chemical Geology, 2008Co-Authors: Carla M Koretsky, Melanie Haveman, Angel Cuellar, Lauren Beuving, Terri Shattuck, Mark WagnerAbstract:Abstract The influence of Spartina alterniflora and Juncus roemarianus on saltmarsh sediment pore water geochemistry was investigated during summer at four sites in a saltmarsh on Sapelo Island, GA, USA. Pore waters were collected from each site at 1–2 cm intervals, to a depth of 50 cm, and analyzed for pH, alkalinity, dissolved manganese, ferric iron, ferrous iron, total sulfide, sulfate, phosphate, ammonium, calcium, magnesium and potassium. The most compressed vertical Redox Stratification occurs at a short Spartina site, followed closely by an adjacent Juncus site. Both sites have shallow oxic and suboxic zones, with sulfidic conditions only a few centimeters or less from the sediment water interface. The densely vegetated Juncus site is inferred to have greater primary productivity and organic matter turnover compared to the short Spartina site. More radial oxygen loss is postulated to occur in the subsurface of the Juncus site, leading to reoxidation of reduced species, more acidic conditions and less accumulation of dissolved sulfide, ammonium and oxidizable-Fe in the solid phase compared to the adjacent short Spartina site. A creekside site vegetated by tall Spartina has the most oxidized sediments, followed by an adjacent unvegetated site. Both of these sites are dominated by suboxic pore waters in most of the upper 50 cm. Subsurface injection of oxygen via roots at the densely vegetated tall Spartina site is inferred to create more acidic pore waters with significantly less accumulation of reduced solutes, including ammonium and alkalinity, compared to the adjacent unvegetated creekside site. Fe and Mn reduction are expected to be significant processes in the bulk near-surface sediments of the tall Spartina and unvegetated sites and within rhizosphere sediments at the tall Spartina and Juncus sites. This study demonstrates the significant influence of Juncus roemarianus and Spartina alterniflora on saltmarsh sediment pore water geochemistry, with important implications for nutrient and trace metal mobility and bioavailability. Future work is needed to explore differences in organic matter concentration and especially lability in the subsurface of saltmarsh sites with varying types and densities of vegetation.
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Influence of Spartina andjuncus on Saltmarsh Sediments. I. Pore Water Geochemistry
Chemical Geology, 2008Co-Authors: Carla M Koretsky, Melanie Haveman, Angel Cuellar, Lauren Beuving, Terri Shattuck, Mark WagnerAbstract:The influence of Spartina altemiflora andjuncus roemarianus on saltmarsh sediment pore water geochemistry was investigated during summer at four sites in a saltmarsh on Sapelo Island, GA, USA. Pore waters were collected from each site at 1-2 cm intervals, to a depth of 50 cm, and analyzed for pH, alkalinity, dissolved manganese, ferric iron, ferrous iron, total sulfide, sulfate, phosphate, ammonium, calcium, magnesium and potassium. The most compressed vertical Redox Stratification occurs at a short Spartina site, followed closely by an adjacent Juncus site. Both sites have shallow oxic and suboxic zones, with sulfidic conditions only a few centimeters or less from the sediment water interface. The densely vegetated Juncus site is inferred to have greater primary productivity and organic matter turnover compared to the short Spartina site. More radial oxygen loss is postulated to occur in the subsurface of the Juncus site, leading to reoxidation of reduced species, more acidic conditions and less accumulation of dissolved sulfide, ammonium and oxidizable-Fe in the solid phase compared to the adjacent short Spartina site. A creekside site vegetated by tall Spartina has the most oxidized sediments, followed by an adjacent unvegetated site. Both of these sites are dominated by suboxic pore waters in most of the upper 50 cm. Subsurface injection of oxygen via roots at the densely vegetated tall Spartina site is inferred to create more acidic pore waters with significantly less accumulation of reduced solutes, including ammonium and alkalinity, compared to the adjacent unvegetated creekside site. Fe and Mn reduction are expected to be significant processes in the bulk near-surface sediments of the tall Spartina and unvegetated sites and within rhizosphere sediments at the tall Spartina and Juncus sites. This study demonstrates the significant influence of Juncus roemarianus and Spartina alterniflora on saltmarsh sediment pore water geochemistry, with important implications for nutrient and trace metal mobility and bioavailability. Future work is needed to explore differences in organic matter concentration and especially lability in the subsurface of saltmarsh sites with varying types and densities of vegetation.
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Seasonal variations in pore water and sediment geochemistry of littoral lake sediments (Asylum Lake, MI, USA)
Geochemical Transactions, 2006Co-Authors: Carla M Koretsky, Johnson R. Haas, Douglas Miller, Noah T. NdengaAbstract:Background Seasonal changes in pore water and sediment Redox geochemistry have been observed in many near-surface sediments. Such changes have the potential to strongly influence trace metal distribution and thus create seasonal fluctuations in metal mobility and bioavailability. Results Seasonal trends in pore water and sediment geochemistry are assessed in the upper 50 cm of littoral kettle lake sediments. Pore waters are always Redox stratified, with the least compressed Redox Stratification observed during fall and the most compressed Redox Stratification observed during summer. A 2-step sequential sediment extraction yields much more Fe in the first step, targeted at amorphous Fe(III) (hydr)oxides (AEF), then in the second step, which targets Fe(II) monosulfides. Fe extracted in the second step is relatively invariant with depth or season. In contrast, AEF decreases with sediment depth, and is seasonally variable, in agreement with changes in Redox Stratification inferred from pore water profiles. A 5-step Tessier extraction scheme was used to assess metal association with operationally-defined exchangeable, carbonate, iron and manganese oxide (FMO), organic/sulfide and microwave-digestible residual fractions in cores collected during winter and spring. Distribution of metals in these two seasons is similar. Co, As, Cd, and U concentrations approach detection limits. Fe, Cu and Pb are mostly associated with the organics/sulfides fraction. Cr and Zn are mostly associated with FMO. Mn is primarily associated with carbonates, and Co is nearly equally distributed between the FMO and organics/sulfide fractions. Conclusion This study clearly demonstrates that near-surface lake sediment pore water Redox Stratification and associated solid phase geochemistry vary significantly with season. This has important ramifications for seasonal changes in the bioavailability and mobility of trace elements. Without rate measurements, it is not possible to quantify the contribution of various processes to natural organic matter degradation. However, the pore water and solid phase data suggest that iron reduction and sulfate reduction are the dominant pathways in the upper 50 cm of these sediments.
Timothy W Lyons - One of the best experts on this subject based on the ideXlab platform.
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revisiting the depositional environment of the neoproterozoic callanna group south australia
Precambrian Research, 2019Co-Authors: Eva E Stueken, Roger Buick, Timothy W LyonsAbstract:Abstract The Callanna Group was deposited around 800 million years ago (Ma) during an interval in Earth’s history that saw a transition towards a more oxygenated atmosphere, increasing biodiversity among eukaryotic microfossils and climatic perturbations culminating in low-latitude glaciations. Previous researchers proposed that the Callanna basin was lacustrine and highly alkaline, which could provide important new insights into environmental cause-effect relationships at this time. To further interrogate these records, we examined standard biogeochemical proxies, including organic carbon and nitrogen isotopes, iron speciation, metal abundances and carbonate-associated sulfate. Much of the primary information has been lost because the rocks of the Callanna Group have experienced extensive metamorphism up to amphibolite facies and are altered by modern weathering. However, relics of these proxies, combined with sedimentological features, preserve evidence of Redox Stratification within this basin. Furthermore, our observations, in particular weakly fractionated nitrogen isotopes and abundant gypsum pseudomorphs, are incompatible with the interpretation of high alkalinity. The high salt content and occurrences of tidal indicators are most parsimoniously explained by frequent incursions of seawater. Thus, the Callanna Group cannot speak straightforwardly to environmental conditions in non-marine habitats at this time. Lastly, the absence of a large carbon isotope anomaly indicates that these rocks do not correlate with the Bitter Springs Formation.
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Effects of pH on Redox proxies in a Jurassic rift lake: Implications for interpreting environmental records in deep time
Geochimica et Cosmochimica Acta, 2019Co-Authors: Eva E Stueken, Gordon D Love, Aaron M. Martinez, Paul E. Olsen, Steve Bates, Timothy W LyonsAbstract:Abstract It is widely agreed that the Earth’s atmosphere and oceans have undergone major Redox changes over the last 2.5 billion years. However, the magnitude of these shifts remains a point of debate because it is difficult to reconstruct concentrations of dissolved O2 from indirect proxies in sedimentary archives. In this study, we show that an additional complicating factor that is rarely considered may be the pH of the water column. We analyzed rock samples from the early Jurassic Towaco Formation in the Newark basin (eastern USA), comprising deposits of a rift lake that became temporarily Redox stratified. New biomarker evidence points to increasingly saline aquatic conditions during the second half of the lake’s history. Salinity Stratification likely induced Redox Stratification, consistent with the disappearance of macrofauna at this time. Distinctive lipid biomarker assemblages and stable nitrogen isotope data support previous mineralogical indications that the lake was alkaline (pH ≥ 9) during its saline episode. Despite the biomarker and macrofaunal evidence for anoxia, ratios of Fe/Al and FeHR/FeT show only small to no enrichments in the anoxic horizon compared to oxic facies in the same section – counter to what is commonly observed in anoxic marine settings. Molybdenum, As, V, U and to some degree Cd show enrichments in the anoxic interval, whereas Co, Ni, Cu, Zn and Cr do not. These patterns are most parsimoniously explained by differential pH effects on the solubility of these elements. Extrapolating from these observations in lacustrine strata, we speculate that a secular increase in seawater pH over Earth’s history as recently proposed may have helped modulate the magnitude of trace metal enrichments in marine shales, although other factors such as atmospheric and oceanic Redox likely dominated the observed enrichment patterns. Further, a decrease in the solubility of ferrous iron, a major O2 sink, with increasing pH may have contributed to ocean oxygenation. In summary, our results highlight the potential importance of pH in influencing global biogeochemical cycles for multiple elements, including the ancient nitrogen isotope record.
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Patterns of local and global Redox variability during the Cenomanian–Turonian Boundary Event (Oceanic Anoxic Event 2) recorded in carbonates and shales from central Italy
Sedimentology, 2017Co-Authors: Jeremy D Owens, Timothy W Lyons, Dalton S. Hardisty, Christopher M Lowery, Bridget K. Lee, Hc JenkynsAbstract:Careful evaluation of the local geochemical conditions in past marine settings can provide a window to the average Redox state of the global ocean during episodes of extensive organic-carbon deposition. These comparisons aid in identifying the interplay between climate and biotic feedbacks contributing to and resulting from these events. Well-documented examples are known from the Mesozoic Era, which is characterized by episodes of widespread organic-carbon deposition known as Oceanic Anoxic Events. This organic-carbon burial typically leads to coeval positive carbon-isotope excursions. Geochemical data are presented here for several palaeoRedox proxies (Cr/Ti, V, Mo, Zn, Mn, Fe speciation, I/Ca and sulphur isotopes) from a section exposed at Furlo in the Marche–Umbrian Apennines of Italy that spans the Cenomanian–Turonian boundary. Here, Oceanic Anoxic Event 2 is represented by a ca 1 m thick radiolarian-rich millimetre-laminated organic-rich shale known locally as the Bonarelli Level. Iron speciation data for thin organic-rich intervals observed below the Bonarelli Level imply a local Redox shift going into the Oceanic Anoxic Event, with ferruginous conditions (i.e. anoxic with dissolved ferrous iron) transiently developed prior to the event and euxinia (i.e. anoxic and sulphidic bottom waters) throughout the event itself. Pre- Oceanic Anoxic Event enrichments of elements sensitive to anoxic water columns were due to initial development of locally ferruginous bottom waters as a precursor to the event. However, the greater global expanse of dysoxic to euxinic conditions during the Oceanic Anoxic Event greatly reduced Redox-sensitive trace-metal concentrations in seawater. Pyrite-sulfur isotopes document a positive shift leading into the OAE. Carbonate I/Ca ratios were generally low, suggesting locally reduced bottom water oxygen conditions preceding the event and relatively increased O2 concentrations post-event. Combined, the Furlo geochemical data suggest a Redox-stratified water column with oxic surface waters and a shallow chemocline overlying locally ferruginous bottom waters preceding the event, globally widespread euxinic bottom waters during the Oceanic Anoxic Event, followed by chemocline shallowing but sustained local Redox Stratification following the event. This article is protected by copyright. All rights reserved.
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patterns of local and global Redox variability during the cenomanian turonian boundary event oceanic anoxic event 2 recorded in carbonates and shales from central italy
Sedimentology, 2017Co-Authors: Jeremy D Owens, Timothy W Lyons, Dalton S. Hardisty, Christopher M Lowery, Bridget Lee, Hc JenkynsAbstract:Careful evaluation of the local geochemical conditions in past marine settings can provide a window to the average Redox state of the global ocean during episodes of extensive organic-carbon deposition. These comparisons aid in identifying the interplay between climate and biotic feedbacks contributing to and resulting from these events. Well-documented examples are known from the Mesozoic Era, which is characterized by episodes of widespread organic-carbon deposition known as Oceanic Anoxic Events. This organic-carbon burial typically leads to coeval positive carbon-isotope excursions. Geochemical data are presented here for several palaeoRedox proxies (Cr/Ti, V, Mo, Zn, Mn, Fe speciation, I/Ca and sulphur isotopes) from a section exposed at Furlo in the Marche–Umbrian Apennines of Italy that spans the Cenomanian–Turonian boundary. Here, Oceanic Anoxic Event 2 is represented by a ca 1 m thick radiolarian-rich millimetre-laminated organic-rich shale known locally as the Bonarelli Level. Iron speciation data for thin organic-rich intervals observed below the Bonarelli Level imply a local Redox shift going into the Oceanic Anoxic Event, with ferruginous conditions (i.e. anoxic with dissolved ferrous iron) transiently developed prior to the event and euxinia (i.e. anoxic and sulphidic bottom waters) throughout the event itself. Pre- Oceanic Anoxic Event enrichments of elements sensitive to anoxic water columns were due to initial development of locally ferruginous bottom waters as a precursor to the event. However, the greater global expanse of dysoxic to euxinic conditions during the Oceanic Anoxic Event greatly reduced Redox-sensitive trace-metal concentrations in seawater. Pyrite-sulfur isotopes document a positive shift leading into the OAE. Carbonate I/Ca ratios were generally low, suggesting locally reduced bottom water oxygen conditions preceding the event and relatively increased O2 concentrations post-event. Combined, the Furlo geochemical data suggest a Redox-stratified water column with oxic surface waters and a shallow chemocline overlying locally ferruginous bottom waters preceding the event, globally widespread euxinic bottom waters during the Oceanic Anoxic Event, followed by chemocline shallowing but sustained local Redox Stratification following the event. This article is protected by copyright. All rights reserved.
Hc Jenkyns - One of the best experts on this subject based on the ideXlab platform.
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Patterns of local and global Redox variability during the Cenomanian–Turonian Boundary Event (Oceanic Anoxic Event 2) recorded in carbonates and shales from central Italy
Sedimentology, 2017Co-Authors: Jeremy D Owens, Timothy W Lyons, Dalton S. Hardisty, Christopher M Lowery, Bridget K. Lee, Hc JenkynsAbstract:Careful evaluation of the local geochemical conditions in past marine settings can provide a window to the average Redox state of the global ocean during episodes of extensive organic-carbon deposition. These comparisons aid in identifying the interplay between climate and biotic feedbacks contributing to and resulting from these events. Well-documented examples are known from the Mesozoic Era, which is characterized by episodes of widespread organic-carbon deposition known as Oceanic Anoxic Events. This organic-carbon burial typically leads to coeval positive carbon-isotope excursions. Geochemical data are presented here for several palaeoRedox proxies (Cr/Ti, V, Mo, Zn, Mn, Fe speciation, I/Ca and sulphur isotopes) from a section exposed at Furlo in the Marche–Umbrian Apennines of Italy that spans the Cenomanian–Turonian boundary. Here, Oceanic Anoxic Event 2 is represented by a ca 1 m thick radiolarian-rich millimetre-laminated organic-rich shale known locally as the Bonarelli Level. Iron speciation data for thin organic-rich intervals observed below the Bonarelli Level imply a local Redox shift going into the Oceanic Anoxic Event, with ferruginous conditions (i.e. anoxic with dissolved ferrous iron) transiently developed prior to the event and euxinia (i.e. anoxic and sulphidic bottom waters) throughout the event itself. Pre- Oceanic Anoxic Event enrichments of elements sensitive to anoxic water columns were due to initial development of locally ferruginous bottom waters as a precursor to the event. However, the greater global expanse of dysoxic to euxinic conditions during the Oceanic Anoxic Event greatly reduced Redox-sensitive trace-metal concentrations in seawater. Pyrite-sulfur isotopes document a positive shift leading into the OAE. Carbonate I/Ca ratios were generally low, suggesting locally reduced bottom water oxygen conditions preceding the event and relatively increased O2 concentrations post-event. Combined, the Furlo geochemical data suggest a Redox-stratified water column with oxic surface waters and a shallow chemocline overlying locally ferruginous bottom waters preceding the event, globally widespread euxinic bottom waters during the Oceanic Anoxic Event, followed by chemocline shallowing but sustained local Redox Stratification following the event. This article is protected by copyright. All rights reserved.
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Patterns of local and global Redox variability during the Cenomanian–Turonian Boundary Event (Oceanic Anoxic Event 2) recorded in carbonates and shales from central Italy
'Wiley', 2017Co-Authors: Jd Owens, Tw Lyons, Ds Hardisty, Cm Lowery, Lu Z, Lee B, Hc JenkynsAbstract:Careful evaluation of the local geochemical conditions in past marine settings can provide a window to the average Redox state of the global ocean during episodes of extensive organic-carbon deposition. These comparisons aid in identifying the interplay between climate and biotic feedbacks contributing to and resulting from these events. Well-documented examples are known from the Mesozoic Era, which is characterized by episodes of widespread organic-carbon deposition known as Oceanic Anoxic Events (OAEs). This organic-carbon burial typically leads to coeval positive carbon-isotope excursions. Geochemical data are presented here for several palaeoRedox proxies (Cr/Ti, V, Mo, Zn, Mn, Fe speciation, I/Ca and sulfur isotopes) from a section exposed at Furlo in the Marche–Umbrian Apennines of Italy that spans the Cenomanian-Turonian boundary. Here, OAE 2 is represented by a ~1-m thick radiolarian-rich millimetre-laminated organic-rich shale known locally as the Bonarelli Level. Iron speciation data for thin organic-rich intervals observed below the Bonarelli Level imply a local Redox shift going into the OAE, with ferruginous conditions (i.e., anoxic with dissolved ferrous iron) transiently developed prior to the event and euxinia (i.e., anoxic and sulfidic bottom waters) throughout the event itself. Pre-OAE enrichments of elements sensitive to anoxic water columns were due to initial development of locally ferruginous bottom waters as a precursor to the event. However, the greater global expanse of dysoxic to euxinic conditions during the OAE greatly reduced Redox-sensitive trace-metal concentrations in seawater. Carbonate I/Ca ratios were generally low, suggesting locally reduced bottom water oxygen conditions preceding the event and relatively increased O2 concentrations post-event. Combined, the Furlo geochemical data suggest a Redox-stratified water column with oxic surface waters and a shallow chemocline overlying locally ferruginous bottom waters preceding the event, globally widespread euxinic bottom waters during the OAE, followed by chemocline shallowing but sustained local Redox Stratification following the event
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patterns of local and global Redox variability during the cenomanian turonian boundary event oceanic anoxic event 2 recorded in carbonates and shales from central italy
Sedimentology, 2017Co-Authors: Jeremy D Owens, Timothy W Lyons, Dalton S. Hardisty, Christopher M Lowery, Bridget Lee, Hc JenkynsAbstract:Careful evaluation of the local geochemical conditions in past marine settings can provide a window to the average Redox state of the global ocean during episodes of extensive organic-carbon deposition. These comparisons aid in identifying the interplay between climate and biotic feedbacks contributing to and resulting from these events. Well-documented examples are known from the Mesozoic Era, which is characterized by episodes of widespread organic-carbon deposition known as Oceanic Anoxic Events. This organic-carbon burial typically leads to coeval positive carbon-isotope excursions. Geochemical data are presented here for several palaeoRedox proxies (Cr/Ti, V, Mo, Zn, Mn, Fe speciation, I/Ca and sulphur isotopes) from a section exposed at Furlo in the Marche–Umbrian Apennines of Italy that spans the Cenomanian–Turonian boundary. Here, Oceanic Anoxic Event 2 is represented by a ca 1 m thick radiolarian-rich millimetre-laminated organic-rich shale known locally as the Bonarelli Level. Iron speciation data for thin organic-rich intervals observed below the Bonarelli Level imply a local Redox shift going into the Oceanic Anoxic Event, with ferruginous conditions (i.e. anoxic with dissolved ferrous iron) transiently developed prior to the event and euxinia (i.e. anoxic and sulphidic bottom waters) throughout the event itself. Pre- Oceanic Anoxic Event enrichments of elements sensitive to anoxic water columns were due to initial development of locally ferruginous bottom waters as a precursor to the event. However, the greater global expanse of dysoxic to euxinic conditions during the Oceanic Anoxic Event greatly reduced Redox-sensitive trace-metal concentrations in seawater. Pyrite-sulfur isotopes document a positive shift leading into the OAE. Carbonate I/Ca ratios were generally low, suggesting locally reduced bottom water oxygen conditions preceding the event and relatively increased O2 concentrations post-event. Combined, the Furlo geochemical data suggest a Redox-stratified water column with oxic surface waters and a shallow chemocline overlying locally ferruginous bottom waters preceding the event, globally widespread euxinic bottom waters during the Oceanic Anoxic Event, followed by chemocline shallowing but sustained local Redox Stratification following the event. This article is protected by copyright. All rights reserved.
Zhiquan Li - One of the best experts on this subject based on the ideXlab platform.
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earth s youngest banded iron formation implies ferruginous conditions in the early cambrian ocean
Scientific Reports, 2018Co-Authors: Mengtian Zheng, Leslie J Robbins, John F. Slack, Zhiquan Li, Noah J Planavsky, Lianchang Zhang, Kurt O. KonhauserAbstract:It has been proposed that anoxic and iron-rich (ferruginous) marine conditions were common through most of Earth history. This view represents a major shift in our understanding of the evolution of marine chemistry. However, thus far, evidence for ferruginous conditions comes predominantly from Fe-speciation data. Given debate over these records, new evidence for Fe-rich marine conditions is a requisite if we are to shift our view regarding evolution of the marine Redox landscape. Here we present strong evidence for ferruginous conditions by describing a suite of Fe-rich chemical sedimentary rocks-banded iron formation (BIF)--deposited during the Early Cambrian in western China. Specifically, we provide new U-Pb geochronological data that confirm a depositional age of ca. 527 Ma for this unit, as well as rare earth element (REE) data are consistent with anoxic deposition. Similar to many Algoma-type Precambrian iron formations, these Early Cambrian sediments precipitated in a back-arc rift basin setting, where hydrothermally sourced iron drove the deposition of a BIF-like protolith, the youngest ever reported of regional extent without direct links to volcanogenic massive sulphide (VMS) deposits. Their presence indicates that marine environments were still characterized by chemical- and Redox-Stratification, thus supporting the view that-despite a dearth of modern marine analogues-ferruginous conditions continued to locally be a feature of early Phanerozoic seawater.
Kurt O. Konhauser - One of the best experts on this subject based on the ideXlab platform.
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earth s youngest banded iron formation implies ferruginous conditions in the early cambrian ocean
Scientific Reports, 2018Co-Authors: Mengtian Zheng, Leslie J Robbins, John F. Slack, Zhiquan Li, Noah J Planavsky, Lianchang Zhang, Kurt O. KonhauserAbstract:It has been proposed that anoxic and iron-rich (ferruginous) marine conditions were common through most of Earth history. This view represents a major shift in our understanding of the evolution of marine chemistry. However, thus far, evidence for ferruginous conditions comes predominantly from Fe-speciation data. Given debate over these records, new evidence for Fe-rich marine conditions is a requisite if we are to shift our view regarding evolution of the marine Redox landscape. Here we present strong evidence for ferruginous conditions by describing a suite of Fe-rich chemical sedimentary rocks-banded iron formation (BIF)--deposited during the Early Cambrian in western China. Specifically, we provide new U-Pb geochronological data that confirm a depositional age of ca. 527 Ma for this unit, as well as rare earth element (REE) data are consistent with anoxic deposition. Similar to many Algoma-type Precambrian iron formations, these Early Cambrian sediments precipitated in a back-arc rift basin setting, where hydrothermally sourced iron drove the deposition of a BIF-like protolith, the youngest ever reported of regional extent without direct links to volcanogenic massive sulphide (VMS) deposits. Their presence indicates that marine environments were still characterized by chemical- and Redox-Stratification, thus supporting the view that-despite a dearth of modern marine analogues-ferruginous conditions continued to locally be a feature of early Phanerozoic seawater.
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Earth’s youngest banded iron formation implies ferruginous conditions in the Early Cambrian ocean
Scientific reports, 2018Co-Authors: Lianchang Zhang, Mengtian Zheng, Leslie J Robbins, John F. Slack, Noah J Planavsky, Chun Ji Xue, Mingtian Zhu, Kurt O. KonhauserAbstract:It has been proposed that anoxic and iron-rich (ferruginous) marine conditions were common through most of Earth history. This view represents a major shift in our understanding of the evolution of marine chemistry. However, thus far, evidence for ferruginous conditions comes predominantly from Fe-speciation data. Given debate over these records, new evidence for Fe-rich marine conditions is a requisite if we are to shift our view regarding evolution of the marine Redox landscape. Here we present strong evidence for ferruginous conditions by describing a suite of Fe-rich chemical sedimentary rocks—banded iron formation (BIF)—-deposited during the Early Cambrian in western China. Specifically, we provide new U-Pb geochronological data that confirm a depositional age of ca. 527 Ma for this unit, as well as rare earth element (REE) data are consistent with anoxic deposition. Similar to many Algoma-type Precambrian iron formations, these Early Cambrian sediments precipitated in a back-arc rift basin setting, where hydrothermally sourced iron drove the deposition of a BIF-like protolith, the youngest ever reported of regional extent without direct links to volcanogenic massive sulphide (VMS) deposits. Their presence indicates that marine environments were still characterized by chemical- and Redox-Stratification, thus supporting the view that—despite a dearth of modern marine analogues—ferruginous conditions continued to locally be a feature of early Phanerozoic seawater.