Assessing the utility of Fe/Al and Fe-speciation to record water column redox conditions in carbonate-rich sediments

Abstract The aim of this research is to reconstruct palaeoredox conditions during sedimentation of the Jeleniów Claystone Formation deposits, using framboid pyrite diameter measurements. Analysis of pyrite framboids diameter distribution is an effective method in the palaeoenvironmental interpretation which allow for a more detailed insight into the redox conditions, and thus the distinction between euxinic, dysoxic and anoxic conditions. Most of the samples is characterized by framboid indicators typical for anoxic/euxinic conditions in the water column, with average (mean) values ranging from 5.29 to 6.02 μm and quite low standard deviation (SD) values ranging from 1.49 to 3.0. The remaining samples have shown slightly higher values of framboid diameter typical for upper dysoxic conditions, with average values (6.37 to 7.20 μm) and low standard deviation (SD) values (1.88 to 2.88). From the depth of 75.5 m till the shallowest part of the Jeleniów Claystone Formation, two samples have been examined and no framboids has been detected. Because secondary weathering should be excluded, the lack of framboids possibly indicates oxic conditions in the water column. Oxic conditions continue within the Wólka Formation based on the lack of framboids in the ZB 51.6 sample

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Water column stability as an important factor controlling nitrite-dependent anaerobic methane oxidation in stratified lake basins

10.1101/2021.11.09.467825 ◽

2021 ◽

Author(s):

Guangyi Su ◽

Moritz Lehmann ◽

Jana Tischer ◽

Yuki Weber ◽

Jean-Claude Walser ◽

...

Keyword(s):

Water Column ◽

Electron Acceptor ◽

Nitrite Reduction ◽

Redox Conditions ◽

Series Data ◽

Anaerobic Oxidation Of Methane ◽

The South ◽

South Basin ◽

Water Column Stability ◽

The North

Anaerobic oxidation of methane (AOM) with nitrate/nitrite as the terminal electron acceptor may play an important role in mitigating methane emissions from lacustrine environments to the atmosphere. We investigated AOM in the water column of two connected but hydrodynamically contrasting basins of a south-alpine lake in Switzerland (Lake Lugano). The North Basin is permanently stratified with year-round anoxic conditions below 120 m water depth, while the South Basin undergoes seasonal stratification with the development of bottom water anoxia during summer. We show that below the redoxcline of the North Basin a substantial fraction of methane was oxidized coupled to nitrite reduction by Candidatus Methylomirabilis. Incubation experiments with 14CH4 and concentrated biomass from showed at least 43-52%-enhanced AOM rates with added nitrate/nitrite as electron acceptor. Multiannual time series data on the population dynamics of Candidatus Methylomirabilis in the North Basin following an exceptional mixing event in 2005/2006 revealed their requirement for lasting stable low redox-conditions to establish. In the South Basin, on the other hand, we did not find molecular evidence for nitrite-dependent methane oxidizing bacteria. Our data suggest that here the dynamic mixing regime with fluctuating redox conditions is not conducive to the development of a stable population of relatively slow-growing Candidatus Methylomirabilis, despite a hydrochemical framework that seems more favorable for nitrite-dependent AOM than in the North Basin. We predict that the importance of N-dependent AOM in freshwater lakes will likely increase in future because of longer thermal stratification periods and reduced mixing caused by global warming.

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Iodine speciation and cycling in limnic systems: observations from a humic rich headwater lake (Mummelsee)

Biogeosciences Discussions ◽

10.5194/bgd-5-25-2008 ◽

2008 ◽

Vol 5 (1) ◽

pp. 25-64 ◽

Cited By ~ 6

Author(s):

B. S. Gilfedder ◽

M. Petri ◽

H. Biester

Keyword(s):

Water Column ◽

Sediment Core ◽

Redox Conditions ◽

Low Oxygen ◽

Total Iodine ◽

Iodine Species ◽

Hypoxic Conditions ◽

Iodine Speciation ◽

Oxygen Conditions ◽

Co Precipitation

Abstract. Iodine undergoes several redox changes in the natural environment, existing as iodate, iodide, and covalently bound to organic matter. While considerable attention has been given to iodine speciation and cycling in the marine environment, very little is known about iodine cycling and speciation in terrestrial fresh water systems. Here we show iodine speciation (measured by IC-ICP-MS) data from one year of monthly sampling of a small humic rich lake in the Black Forest (Mummelsee) under varying redox conditions. The aim was to elucidate the seasonal cycles of iodine species in the lake water column and to quantify both inorganic and organic iodine species. A sediment core was also collected for iodine analysis. Total iodine levels in the Mummelsee averaged 1.93±0.3 μg l−1. Organo-I was the dominant species in the lake, making up on average 85±7% of the total iodine. No strong seasonal variation in organo-I was observed, with only small variations occurring in the epi- and hypolimnion. Iodide was scavenged from the epilimnion during the summer and autumn, which could be related to (micro)biological uptake and co-precipitation. This was also suggested by the high iodine levels in the sediment core (av. 11.8±1.7 mg kg −1). In the hypolimnion, a strong flux of iodide was observed from the sediments into the water column during anoxic and hypoxic conditions, observed during the summer, autumn and, in the bottom 2 m, the winter. This iodide flux and is thought to occur during decomposition of biological material. Iodate levels in the epilimnion increased consistently over the year, whereas it was reduced below detection limits in the hypolimnion during low oxygen conditions. The winter partial turnover lead to reintroduction of oxygen into the hypolimnion and the formation of iodate and organo-I, as well as removal of iodide. In conclusions, iodine cycling in the Mummelsee was controlled by organo-I, although redox conditions and perhaps biological activity were also important, particularly in the hypolimnion during stratification.

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Fe isotope and Fe speciation study of water column redox dynamics during Eastern Mediterranean sapropel events S5 and S7

10.5194/egusphere-egu2020-1864 ◽

2020 ◽

Author(s):

Alan Matthews ◽

Ayelet Benkovitz ◽

Nadya Teutsch ◽

Simon Poulton ◽

Miryam Bar-Matthews ◽

...

Keyword(s):

Mediterranean Sea ◽

Water Column ◽

Black Sea ◽

Eastern Mediterranean ◽

The Black Sea ◽

Eastern Mediterranean Sea ◽

Positive Balance ◽

Fe Speciation ◽

Bottom Waters ◽

Oxide Minerals

Sapropels S5 and S7 formed in the semi-enclosed Eastern Mediterranean Sea &#160;during peak interglacial periods MIS5e and MIS7a, respectively. This study investigates the dynamics of &#160;water column redox change during their formation, through Fe isotope and Fe speciation studies of cores taken at 2550 m depth at site ODP-967 south of Cyprus. Both sapropels show an inverse correlation between &#948;56Fe and FeT/Al, with slopes mostly matching that found for the Black Sea, pointing to a benthic shelf to basin shuttle of Fe and subsequent precipitation of Fe sulphides in highly euxinic bottom waters. An exception to these Black Sea-type trends occurs during the later, peak stages of S7, where the negative &#948;56Fe - FeT/Al slope shallows. Fe speciation studies reveal that the dominant highly reactive Fe phase (FeHR) in the sapropels is pyrite, with Fe (oxyhydr)oxides forming the second major mineral component. FeHR/FeT plots show increased strengthening of anoxic water conditions during the transformation from pre-sapropel sediment into the sapropel. Nevertheless, despite the evidence for highly euxinic conditions from both Fe isotopes and high Mo concentrations in the sapropels, Fepy/FeHR ratios remain below values commonly used to identify water column euxinia. This apparent contradiction is ascribed to the sedimentary preservation of a high flux of crystalline Fe (oxyhydr)oxide minerals to the basin, which resulted in a relatively low degree of sulphidation, despite the presence of euxinic bottom waters.&#160; Thus, the operationally defined ferruginous/euxinic boundary for Eastern Mediterranean Sea sapropels is better placed at Fepy/FeHR = 0.6, which is somewhat below the usually ascribed lower limit of 0.7. Consistent with the significant presence of crystalline Fe (oxyhydr)oxides, the change in the &#948;56Fe - FeT/Al slope during peak S7 is ascribed to an enhanced monsoon-driven flux of detrital Fe(III) oxides from the River Nile into the Eastern Mediterranean basin. The euxinic water column conditions that developed in sapropels S5 and S7 are interpreted to reflect the positive balance between dissolved sulphide formation and rates of reductive dissolution of Fe (oxyhydr)oxide minerals. Both of these parameters in turn depend on the extent to which water overturn times are reduced during sapropel formation. Water overturn rate is therefore considered to define the strength of euxinic water column conditions during these periods of organic carbon-rich sedimentation.

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Combining sedimentological, trace metal (Mn, Mo) and molecular evidence for reconstructing past water-column redox conditions: The example of meromictic Lake Cadagno (Swiss Alps)

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2013.06.017 ◽

2013 ◽

Vol 120 ◽

pp. 220-238 ◽

Cited By ~ 44

Author(s):

Stefanie B. Wirth ◽

Adrian Gilli ◽

Helge Niemann ◽

Tais W. Dahl ◽

Damiana Ravasi ◽

...

Keyword(s):

Trace Metal ◽

Water Column ◽

Meromictic Lake ◽

Redox Conditions ◽

Swiss Alps ◽

Molecular Evidence

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Intense molybdenum accumulation in sediments underneath a nitrogenous water column and implications for the reconstruction of paleo-redox conditions based on molybdenum isotopes

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2017.06.048 ◽

2017 ◽

Vol 213 ◽

pp. 400-417 ◽

Cited By ~ 42

Author(s):

Florian Scholz ◽

Christopher Siebert ◽

Andrew W. Dale ◽

Martin Frank

Keyword(s):

Water Column ◽

Redox Conditions ◽

Molybdenum Isotopes

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The Ediacaran ‘Miaohe Member’ of South China: new insights from palaeoredox proxies and stable isotope data

Geological Magazine ◽

10.1017/s0016756821000261 ◽

2021 ◽

pp. 1-15

Author(s):

Paul Bridger ◽

Simon W. Poulton ◽

Ying Zhou ◽

Chao Li ◽

Kun Zhang ◽

...

Keyword(s):

Trace Metal ◽

Water Column ◽

Southern China ◽

Life Forms ◽

Black Shales ◽

Redox Conditions ◽

Geochemical Data ◽

Ecological Niches ◽

Low Oxygen ◽

Reactive Iron

Abstract Throughout the Ediacaran Period, variable water-column redox conditions persisted along productive ocean margins due to a complex interplay between nutrient supply and oceanographic restriction. These changing conditions are considered to have influenced early faunal evolution, with marine anoxia potentially inhibiting the development of the ecological niches necessary for aerobic life forms. To understand this link between oxygenation and evolution, the combined geochemical and palaeontological study of marine sediments is preferable. Located in the Yangtze Gorges region of southern China, lagoonal black shales at Miaohe preserve alga and putative metazoans, including Eoandromeda, a candidate total-group ctenophore, thereby providing one example of where integrated study is possible. We present a multi-proxy investigation into water-column redox variability during deposition of these shales (c. 560–551 Ma). For this interval, reactive iron partitioning indicates persistent water-column anoxia, while trace metal enrichments and other geochemical data suggest temporal fluctuations between ferruginous, euxinic and rare suboxic conditions. Although trace metal and total organic carbon values imply extensive basin restriction, sustained trace metal enrichment and δ15Nsed data indicate periodic access to open-ocean inventories across a shallow-marine sill. Lastly, δ13Corg values of between −35‰ and −40‰ allow at least partial correlation of the shales at Miaohe with Member IV of the Doushantuo Formation. This study provides evidence for fluctuating redox conditions in the lagoonal area of the Yangtze platform during late Ediacaran time. If these low-oxygen environments were regionally characteristic, then the restriction of aerobic fauna to isolated environments can be inferred.

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Lower Wenlock black shales in the northern Holy Cross Mountains, Poland: sedimentary and geochemical controls on the Ireviken Event in a deep marine setting

Geological Magazine ◽

10.1017/s0016756815001065 ◽

2016 ◽

Vol 154 (2) ◽

pp. 247-264 ◽

Cited By ~ 16

Author(s):

JUSTYNA SMOLAREK ◽

WIESŁAW TRELA ◽

DAVID P. G. BOND ◽

LESZEK MARYNOWSKI

Keyword(s):

Organic Carbon ◽

Total Organic Carbon ◽

Water Column ◽

Black Shale ◽

Bottom Water ◽

Black Shales ◽

Redox Conditions ◽

Pyrite Framboids ◽

Redox History ◽

Deposition Conditions

AbstractThe stratigraphic variability and geochemistry of Llandovery/Wenlock (L/W) Series boundary sediments in Poland reveals that hemipelagic sedimentation under an anoxic/euxinic water column was interrupted by low-density bottom currents or detached diluted turbid layers that resulted in intermittent seafloor oxygenation. Total organic carbon values and inorganic proxies throughout the Wilków 1 borehole section suggest variable redox conditions. U/Mo ratios > 1 throughout much of the Aeronian and Telychian stages, together with an absence of pyrite framboids, suggest oxygenated conditions prevailed. However, elevated total organic carbon near the Aeronian/Telychian boundary, together with increased U/Th and V/(V + Ni) ratios and populations of small pyrite framboids are consistent with the development of dysoxic/anoxic conditions at that time. U/Th, V/Cr and V/(V + Ni) ratios, as well as Uauthig and Mo concentrations, suggest that during the Ireviken black shale deposition, bottom-water conditions deteriorated from oxic during Telychian time to mostly suboxic/anoxic immediately prior to the L/W boundary, before a brief reoxygenation at the end of the Ireviken black shale sedimentation in the Sheinwoodian Stage. Rapid fluctuations in U/Mo during the Ireviken Event are characteristic of fluctuating redox conditions that culminated in an anoxic/euxinic seafloor in Sheinwoodian time. Following Ireviken black shale deposition, conditions once again became oxygen deficient with the development of a euxinic zone in the water column. The Aeronian to Sheinwoodian deep-water redox history was unstable, and rapid fluctuations of the chemocline across the L/W Series boundary probably contributed to the Ireviken Event extinctions, which affected mainly pelagic and hemipelagic fauna.

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