Environmental Geochemistry and Health, Journal Year: 2024, Volume and Issue: 46(9)
Published: July 13, 2024
Language: Английский
Chemical Geology, Journal Year: 2024, Volume and Issue: 654, P. 122058 - 122058
Published: March 25, 2024
Cadmium (Cd) isotope signatures (δ114Cd) deduced from modern and ancient marine deposits are often used as a proxy for bioproductivity micronutrient cycling, whereas chromium (Cr) (δ53Cr) potential oxygenation. The Cretaceous—Paleogene (K/Pg) boundary records one of Earth's five big mass extinctions, which contains geochemical fingerprints the Chixculub asteroid impact is coeval with Deccan Trap volcanism. Here we present first time combined record Cd Cr isotopes Danish Basin to interrogate effects on across K/Pg boundary. δ114Cd values range between −0.28‰ 0.27‰ defining an average 0.05‰ ± 0.24 (2σ, n = 87). Authigenic δ53Cr 0.06‰ 1.06‰ define 0.59‰ 0.51 81). An abrupt jump, layer, consistently positively fractionated recorded in Late Maastrichtian white chalks towards less heterogeneous Early Danian carbonates, likely indicates decrease surface water bioproductivity. This accompanied by redox fluctuations column consequence environmental changes either related event and/or volcanic eruptions this Assuming efficient removal through consumption adsorption primary producers, or incorporation into skeleton/shells calcifiers, using fractionation factor reconstruct conditions during Masstrichtian—Early that compatible those oceans, varying 0.17 0.72‰. Overall, Cr-Cd over consistent scenario characterized climate-induced nutrient availability concomitant responses production levels, ultimately proceeding activities influenced ocean's chemistry. We anticipate our results point further studies other stratigraphic sections worldwide reveal extensive Cd-Cr its corresponding collapse decreasing ocean
Language: Английский
Citations
5
Geophysical Research Letters, Journal Year: 2022, Volume and Issue: 49(21)
Published: Oct. 4, 2022
Abstract Chromium stable isotope composition (δ 53 Cr) is a promising tracer for redox conditions throughout Earth's history; however, the geochemical controls of δ Cr have not been assessed in modern redox‐stratified basins. We present new chromium (Cr) concentration and data dissolved, sinking particulate, sediment samples from Lake Cadagno (Switzerland), Proterozoic ocean analog. These demonstrate fractionation during incomplete (non‐quantitative) reduction removal above chemocline, driving isotopically light accumulation euxinic deep waters. Sediment authigenic distinct overlying waters but comparable to average continental crust. New published other basins show analogous patterns. This challenges assumptions paleoredox applications that quantitative limits fractionation. Instead, non‐quantitative leads sedimentary records offset reflecting high oxidative weathering.
Language: Английский
Citations
19
Geochimica et Cosmochimica Acta, Journal Year: 2023, Volume and Issue: 348, P. 239 - 257
Published: March 6, 2023
In the marine sediment record, concentrations and isotope ratios of chromium (Cr) can be used to reconstruct ocean biogeochemical conditions. These reconstructions rely on a detailed understanding chemical pathways that Cr undergoes as it is transferred from water column record. We examined in pore fluids sediments six continental margin sites, which grouped into two basic environments: (1) sites where are oxygenated rich solid phase Mn (herein termed oxic), (2) organic C (Corg)-rich oxygen depleted (anoxic). found lower (maximum 12 nM 124 ppm phase) at oxic compared with anoxic 77 184 ppm). Our findings confirm previously published interpretations dissolved (Brumsack Gieskes, 1983; Shaw et al., 1990). surface sediments, particulate Cr(III) oxidised by oxides, leads elevated co-occurring same depth sediment. Under these oxidising conditions, down-core contain relatively low solid-phase concentrations. speciation reveals most fluid Cr(VI) state. At site oxide-rich rest below an column, oxidative loss bottom lowest estimated burial efficiency here. Corg-rich both phases high concentrations, 40–80% present Cr(III). This enrichment appears tightly linked presence total carbon (TOC) content scavenging (organic) particles column. Combined, data highlight strong dependence sedimentary redox conditions well biological productivity. Based modern we propose compositions authigenic fraction may record combination productivity If confirmed analyses, will add support for notion serve proxy sedimentological Thus, careful assessment impact matter required records.
Language: Английский
Citations
10
Geochemistry Geophysics Geosystems, Journal Year: 2025, Volume and Issue: 26(4)
Published: April 1, 2025
Abstract The Rapitan Group (Northwest Territories, Canada) includes banded iron formation (BIF), an unusual sediment type that is associated with late Neoproterozoic glaciations, in this case, the early Cryogenian Sturtian glaciation. New non‐traditional stable isotope data from jasper and hematite (IF) Cranswick River area contribute new insights regarding water chemistry changes respective depositional basin during glacier advance retreat. Cr signatures are characterized by strongly positively fractionated δ 53 values (+0.68–1.47‰), attesting to oxidized surface waters entire episode. Relatively weakly 114 Cd (−0.02 +0.28‰), absence of organic matter samples, indicate a low bioproductivity BIF deposition. Detailed fluctuations over intermittent retreat cycle recorded studied section, however, reveal ephemeral increase primary production (excursion slightly elevated values) just after deposition diamictite layer, which agrees corresponding values. This evidence attests sensitivity Cd‐Cr double tracer applied BIFs reconstruct basins track climate accompanied glacial episodes. When compared younger (Marinoan/Ediacaran) Urucum Brazil, section differs lack negative Ce anomalies its rare earth element patterns, implying column oxidation was not as strong Marinoan/Ediacaran
Language: Английский
Citations
0
Aquatic Sciences, Journal Year: 2025, Volume and Issue: 87(2)
Published: April 1, 2025
Abstract Lake Cadagno is a meromictic alpine lake characterized by permanent stratification, which creates anoxic environment that supports the growth of anoxygenic phototrophic sulfur bacteria. The seasonality and interseasonality these microorganisms were examined over three-year period (2019–2021) through regular monitoring water column. A variety physical–chemical parameters, including temperature, conductivity, light, oxygen sulfide concentrations, community composition bacteria in chemocline recorded, to observe potential influence external weather conditions. Our findings indicate that, despite lake’s consistent physical chemical exhibited notable variations response environmental factors, changes rainfall light irradiance. Specifically, we observed different dynamics purple (PSB) green (GSB) communities three years monitoring. These underscore complexity biogeochemical cycles lakes impact factors on this ancestral microbial dynamics. results provide valuable insights into stability redox-stratified environments, offering modern analog for ancient aquatic ecosystems. This research emphasizes importance long-term capture interannual assess implications climate change such unique
Language: Английский
Citations
0
Geological Society of America Bulletin, Journal Year: 2024, Volume and Issue: 136(9-10), P. 4005 - 4017
Published: March 4, 2024
Abstract Copper-zinc isotopic excursions in carbonate sedimentary successions are used to trace oceanic chemistry fluctuations that occurred the geological past. However, whether sediments can accurately record Cu-Zn compositions of coeval seawater is still a matter debate. We analyzed well-characterized methane-derived carbonates from drill cores South China Sea decode effect environment on fractionation. All seep have uniform δ65Cuauth values (the per mil deviation 65Cu/63Cu ratio NIST 976 standard; −0.22‰ 0‰) independent environment. In contrast, δ66Znauth 66Zn/64Zn JMC-Lyon standard) precipitated bottom (intense methane seepage; 0.59‰ 1.03‰) significantly higher than those formed pore-water environments (low flux; −0.07‰ 0.41‰). This evidence implies changes affect Zn fractionation sediments. Furthermore, strong environment-dependent proves validity using isotopes as robust proxy for tracing paleo-methane seepage intensity caused by gas hydrate dissociation.
Language: Английский
Citations
2
Chemical Geology, Journal Year: 2024, Volume and Issue: 657, P. 122101 - 122101
Published: April 25, 2024
The Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil) comprises ~600 Ma Fe and Mn deposits, which are among the world's youngest largest Neoproterozoic sedimentary formations (IF; MnF). These have been deposited in a redox-stratified, marine sub-basin (Jacadigo Basin), was strongly influenced by glacial advance/retraction cycles with temporary influx of continental freshwater upwelling metal-enriched deep anoxic seawater. Cr Cd isotopes measured on meticulously separated hematite mesobands from drill core samples relatively homogenous throughout ca. 325 m thick sequence sampled Fm., average authigenic δ53Cr values +0.93 ± 0.24 ‰ (2σ; n = 23) δ114Cd −0.14 0.14 15). significant enrichment Cr, parallel strong enrichments other redox sensitive elements (U, Mo), attests for effective efficient reduction removal processes surface waters during where Fe2+-rich reached oxygenated layer exposed to atmosphere episodic glacier retreat stages. Assuming similar quantitative pathway dissolved iron oxyhydroxides, so-inferred signature Jacadigo Basin water is significantly lower than signatures modern ocean range ~0.4 ~1 even ~0.3 ‰. It possibly reduced primary production levels nutrient utilization rates deposition Late Group, compared today. This despite inferred oxidized that must prevailed this time, as implied positively fractionated isotope pronouncedly negative Ce-anomalies recorded seawater-like, shale-normalized Rare Earth Element Yttrium (REY) patterns exhibited mesobands. Data presented herein speak for: (1) stable, isotopically heavy input at time deposition, implying high atmospheric O2 (2) likely quantitative, reductive incorporation / adsorption Cd, respectively, into/onto precipitating (3) prevalence low concentrations cycles. Banded considered suitable archives reconstructing bioproductivity past depositional basin, including those prevalent conditions, via employing CrCd double tracer iron-rich
Language: Английский
Citations
2
Gondwana Research, Journal Year: 2023, Volume and Issue: 124, P. 39 - 60
Published: July 1, 2023
Cr isotopes recorded in iron formations (IF) are considered to have the potential reflect isotope signatures respective ambient surface seawater. The ∼600 Ma Fe and Mn deposits pertaining Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil), comprise world's youngest largest Neoproterozoic sedimentary (MnF). Shale normalized Rare Earth Element Yttrium (REY) patterns of drillcore samples show flat, positively sloped with absent Europium anomalies near- supra-chondritic Yttrium-Holmium ratios negative Cerium anomalies, which imply intermittent mixing freshwater Redox sensitive element enrichment factors (MoEF, UEF, CrEF) positive correlation, indicating varying redox conditions across Jacadigo Basin, ephemeral euxinic conditions. Urucum IF (δ 53Crauth at: Morraria Grande +0.93 ± 0.34 ‰, 2 σ, n=28; Morro Rabichão +0.5 0.4 n=3; ca. +0.64 n=1) statistically indistinguishable from previously published outcrop at Urucum. Our new data support: (1) a stable supply oxidized potentially continental sources time deposition, implying high atmospheric O2 levels Late Neoproterozoic; (2) insignificant alteration authigenic signals by tropical weathering despite up-concentration leaching carbonates, (3) lack effects that would be associated non-quantitative reduction processes accompanying particulate transport chemical sediments Basin. combined information (isotope)geochemical presented herein speak for deposition IFs restricted, periodically ice-covered stratified sub-basins partial connection open ocean, presence sufficiently oxidative atmosphere promoted continuous waters isotopically heavy landmasses this time.
Language: Английский
Citations
6
Research Square (Research Square), Journal Year: 2024, Volume and Issue: unknown
Published: Feb. 27, 2024
Abstract Lake Cadagno (Switzerland) differs from common alpine lakes, as it consists of two stratified layers water that never vertically mix. This particular environment is a niche for the development ancient anoxygenic microorganisms similar to those populated primordial oceans – which accumulate in lower part chemocline. Yet, linkages between temporal variation abiotic factors, controlling stratification, with phototrophic sulfur bacteria community bacterial layer (BL) remain unclear. We studied intra- and inter-seasonal stability column stratification population dynamics BL three years address this gap. Analyses extended continuous monitoring show redox-stratified environments lake remarkably stable, seemingly unaffected by factors. In contrast, showed significant variability. The distinct weather conditions observed during these strongly influenced composition community. Indeed, especially at intra-seasonal level, main populations monitored different each year. lake's recent history also revealed same trend. fact, over last 35 years, meromixis remained unchanged, while considerable
Language: Английский
Citations
2
Frontiers in Marine Science, Journal Year: 2023, Volume and Issue: 10
Published: May 26, 2023
Chromium (Cr) is a redox-sensitive element and because Cr isotopes are fractionated by redox and/or biological processes, the isotopic composition of ancient marine sediments may be used to infer changes in past seawater oxygenation or productivity. While there appears ‘global correlation’ between dissolved concentration seawater, ongoing debate about relative importance external sources internal cycling on shaping distribution that needs resolved validate efficacy using as paleo proxy. Here, we present full water column depth profiles total (Cr(VI)+Cr(III)) (δ 53 Cr), together with ancillary data, for three stations along transect (GEOTRACES GApr08) across sub-tropical North Atlantic. Concentrations ranged 1.84 2.63 nmol kg -1 , δ values varied from 1.06 1.42‰. Although atmospheric dust, hydrothermal vents seabed have potential modify oceans, based our observations, no clear evidence substantial input these study region although benthic inputs locally important vicinity vents. Subsurface waters (below surface mixed layer 700 m depth) were very slightly depleted (by up ~0.4 ), enriched heavy ~0.14‰), deeper lowest concentrations highest coincided colloidal (0.02 0.2 μm size fraction) Fe. We found direct uptake oligotrophic euphotic zone removal modestly oxygen (O 2 ~130 μmol ). Rather, suggest (probably form Cr(III)) subsurface associated formation colloid aggregates Fe-(oxyhydr)oxides. This process likely enhanced high lithogenic particle load this region, represents previously unrecognized export flux Cr. Regeneration leads subtly increased levels alongside decreased at individual sites, but trend more obvious global scale, decreasing increasing radiocarbon age deep waters, 1.16 ± 0.10‰ (1SD, n=11) Atlantic 0.77 n=25) Pacific waters. Removal relatively isotopically light onto particulate material regeneration back into phase partly accounts systematic relationship discussed other studies.
Language: Английский
Citations
5