Early diagenesis of sulfur in a tropical upwelling system, Cabo Frio, southeastern Brazil

Díaz, Rut; Moreira, Manuel; Mendoza, Ursula; Machado, Wilson; Böttcher, Michael E.; Santos, Helenice; Belem, André L.; Capilla, Ramsés; Escher, Peter; Albuquerque, Ana Luíza Spadano

doi:10.1130/g33111.1

Cited by 20 publications

(5 citation statements)

References 27 publications

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“…Instead, the authigenic oxides forming near the sediment–water interface record a seawater signature. This is supported by a study of sulphur cycling in the CFUS which also concluded that the low degree of pyritization, concentrations of pore water sulfide, and sedimentary reducible sulphur were caused by oxidation processes in the first centimeters of the sedimentary column 38 . Downcore measurements on CF10-01 consistently show low U/Ca values (Fig.…”

Section: Discussionmentioning

confidence: 72%

“…Reductive dissolution of authigenic oxides in the water column can be ruled out because there is no strong oxygen minimum zone in the study area 41 . In addition, sulphur cycling in CFUS suggests oxic conditions of bottom waters and Holocene sediments 38 , as well as the strong positive Ce anomaly and the consistently low U/Ca values also do.…”

Section: Discussionmentioning

confidence: 91%

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Coupled changes in western South Atlantic carbon sequestration and particle reactive element cycling during millennial-scale Holocene climate variability

Dias

Piotrowski

Barbosa

et al. 2021

Sci Rep

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AbstractContinental shelves have the potential to remove atmospheric carbon dioxide via the biological pump, burying it in seafloor sediments. The efficiency of marine carbon sequestration changes rapidly due to variations in biological productivity, organic carbon oxidation, and burial rate. Here we present a high temporal resolution record of marine carbon sequestration changes from a western South Atlantic shelf site sensitive to Brazil Current-driven upwelling. The comparison of biological records to rare earth element (REE) patterns from authigenic oxides shows a strong relationship between higher biological productivity and stronger particle reactive element cycling (i.e. REE cycling) during rapid climate change events. This is the first evidence that authigenic oxides archive past changes in upper ocean REE cycling by the exported organic carbon. In addition, our data suggest that Brazil Current-driven upwelling varies on millennial-scales and in time with continental precipitation anomalies as registered in Brazilian speleothems during the Holocene. This indicates an ocean–atmosphere control on the biological pump, most probably related to South American monsoon system variability.

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Section: Discussionmentioning

confidence: 72%

Section: Discussionmentioning

confidence: 91%

Coupled changes in western South Atlantic carbon sequestration and particle reactive element cycling during millennial-scale Holocene climate variability

Dias

Piotrowski

Barbosa

et al. 2021

Sci Rep

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“…The oxidation stage can take place both during the earliest and later stages of diagenesis (the latter is out of the scope of this paper). Re-oxidation processes of pyrite framboids are common in tropical upwelling area, caused by bioturbation and possible contributions from sulfide-oxidizing bacteria (Diaz et al, 2012, and references therein). It would additionally expand, but also complicate, the process of electron transfer in sediments.…”

Section: Conclusion and Model Of Trichichnusmentioning

confidence: 99%

Fossilized bioelectric wire – the trace fossil Trichichnus

et al. 2015

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The trace fossil Trichichnus is proposed as an indicator of fossil bioelectric bacterial activity at the oxic–anoxic interface zone of marine sediments. This fulfils the idea that such processes, commonly found in the modern realm, should be also present in the geological past. Trichichnus is an exceptional trace fossil due to its very thin diameter (mostly less than 1 mm) and common pyritic filling. It is ubiquitous in some fine-grained sediments, where it has been interpreted as a burrow formed deeper than any other trace fossils, below the redox boundary. Trichichnus, formerly referred to as deeply burrowed invertebrates, has been found as remnant of a fossilized intrasediment bacterial mat that is pyritized. As visualized in 3-D by means of X-ray computed microtomography scanner, Trichichnus forms dense filamentous fabric, which reflects that it is produced by modern large, mat-forming, sulfide-oxidizing bacteria, belonging mostly to Thioploca-related taxa, which are able to house a complex bacterial consortium. Several stages of Trichichnus formation, including filamentous, bacterial mat and its pyritization, are proposed to explain an electron exchange between oxic and suboxic/anoxic layers in the sediment. Therefore, Trichichnus can be considered a fossilized “electric wire”.

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“…Thus, estuarine and coastal sediments tend to be rich in organic matter [30][31][32]. This organic matter can provide energy and electron donors for sulfate reduction, the intensity of methane flux, and other biogeochemical processes [33][34][35]. The intensity of methane flux and sulfate reduction are the main processes of the biogeochemical cycle in estuarine and coastal sediments and are also the foundation of the sedimentary carbon and sulfur biogeochemical cycles [36][37][38].…”

Section: Introductionmentioning

confidence: 99%

Differences in the Sulfate–Methane Transitional Zone in Coastal Pockmarks in Various Sedimentary Environments

Cao

Cai

et al. 2020

Water

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Different types of pockmarks, including single pockmarks, circular pockmarks, elongated pockmarks, chain-type pockmarks, and compound pockmarks, were identified in coastal areas around Fujian, China. The sediments associated with pockmarks were mainly silty clay to clay, with a small quantity of silt with fine sand. The sulfate content in the pore water in the sedimentary layers associated with pockmarks decreased with depth from the surface, whereas the free methane content increased with depth. The interaction between sulfate and methane is well known, but differences in the sulfate–methane transitional zone (SMTZ) were observed in different areas with different hydrologic characteristics. The sedimentary SMTZ of the offshore Zhe-Min mud wedge was shallow, at 50–70 cm below the seafloor. The sedimentary SMTZ was moderately deep (90–115 cm) in the central bay area and deep (180–200 cm) in the sandy area offshore. This variability in SMTZ depth reflects different amounts of free methane gas in the underlying formations, with a shallower SMTZ indicating a higher free methane content. The free methane had δ13C values of −26.47‰ to −8.20‰ and a biogenic hybrid genetic type. The flux of sedimentary gas from the pockmark surfaces, calculated according to Fick’s formula, was 2.89 to 18.85 L/m2·a. The shape, size, and scale of the pockmarks are directly related to the substrate type and the gas production of the underlying strata and thus vary with the sedimentary environment and development stage. Therefore, different types of pockmarks, in various phases of development, are associated with different sedimentary and dynamical conditions. A single circular pockmark is formed by a strong methane flux. As the intensity of methane flux weakens, the pockmark becomes elongated in the direction of the water flow because of long-term erosion induced by regular hydrodynamic forces. Finally, under a weak intensity of methane flux and the influence of complex hydrodynamic conditions, pockmarks merge to form large-scale compound pockmarks.

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Early diagenesis of sulfur in a tropical upwelling system, Cabo Frio, southeastern Brazil

Cited by 20 publications

References 27 publications

Coupled changes in western South Atlantic carbon sequestration and particle reactive element cycling during millennial-scale Holocene climate variability

Coupled changes in western South Atlantic carbon sequestration and particle reactive element cycling during millennial-scale Holocene climate variability

Fossilized bioelectric wire – the trace fossil Trichichnus

Differences in the Sulfate–Methane Transitional Zone in Coastal Pockmarks in Various Sedimentary Environments

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