Molybdenum and uranium geochemistry in continental margin sediments: Paleoproxy potential

McManus, James; Berelson, William M.; Severmann, Silke; Poulson, Rebecca; Hammond, Douglas E.; Klinkhammer, Gary P.; Holm, Chris

doi:10.1016/j.gca.2006.06.1564

Cited by 325 publications

(198 citation statements)

References 112 publications

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“…1A and 2). These values are higher than others record along the southern Chilean coast (41° and 36°) influenced by the OMZ (McManus et al, 2006 andBöning et al, 2005), but similar to previous measurements performed in Mejillones Bay (Valdés, 2004).…”

Section: Mo-u Relationshipsupporting

confidence: 91%

“…1 mL L − 1 ) and 16 mg kg − 1 at 120 m depth (dissolved oxygen < 0.1 mL L − 1 ). These values are higher than those reported by McManus et al (2006) for the OMZ sediments in southern Chile (41° S). The distribution of U in the sediments of Mejillones shows a gentle slope up to 80 m that then increases strongly toward the deepest zone (Fig.…”

Section: Mo-u Relationshipcontrasting

confidence: 72%

“…In the sediments, this metal is related to the diagenesis of Mn (Morford and Emerson, 1999). Many studies have shown that anoxic sediments are rich in Mo (1993;Morford and Emerson, 1999, Adelson et al, 2001and McManus et al, 2006. In Mejillones, the Mo ranged from 0 mg kg − 1 at 20 m depth (dissolved oxygen ca.…”

Section: Mo-u Relationshipmentioning

confidence: 99%

“…On the other hand, in anoxic marine sediments there is no evidence of post-depositional remobilization of U and Mo (Morford et al, 2001). Although post-depositional redistribution of Mo and U has the capacity to alter the primary depositional concentration and concentration ratios of these metals, different studies provide no evidence to suggest any systematic differences in their remobilization potential (Colley and Thomson, 1985;Thomson et al, 1995;McManus et al, 2006 andTribovillard, 2009). …”

Section: Mo-u Relationshipmentioning

confidence: 99%

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Redox conditions in a coastal zone of the Humboldt system (Mejillones, 23° S). Influence on the preservation of redox-sensitive metals

Valdés

Sifeddine

Boussafir

et al. 2014

Journal of Geochemical Exploration

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The distribution of, Co, Mo, Zn, Ni, Cd, U, Cu, Mn, V, Al, Fe, Ti, Total Organic Carbon (TOC) and Total Sulfur (TS) was studied in surface sediments accumulated at the upper limit of the oxygen minimum zone in the northern Humboldt Current (Mejillones Bay), using samples taken during two cruises in May 2002 and October 2004. The time series of dissolved oxygen revealed a seasonal fluctuation of the upper limit of the oxygen minimum zone into the bay.Similar bathymetric distribution curves of the metals measured in the two studied periods in the OMZ off northern Chile suggest that the factors responsible for this distribution are persistent over time. Authigenic metal content was calculated using lithogenic background by determining Metal/Al ratio from local aeolian dust, instead of average shale values, which are classically used for background correction. This more precise assessment allows examination of the source-sink relation of each metal in this coastal zone. Mo preserved in the bottom sediments originates from seawater and accumulates via particulate shuttle, whereas Cd is pre-concentrated in biodetritus. Ni, Mn, V and Fe show a combined behavior.Sulfate reduction is not the most important mechanism affecting metal accumulation in Mejillones Bay, probably due to the presence of Thioploca, which inhibits the pyrite formation and the metal-sulfide reaction.We propose the use of the authigenic Mo/U ratio and a preliminary statistical model to reconstruct the levels of paleoxygenation in the subsurface waters of Mejillones Bay, by analyzing the same metals measured throughout the sedimentary sequences (and using the same statistical procedure), at least to identify extreme variations of the OMZ in this bay of northern Chile.

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Section: Mo-u Relationshipsupporting

confidence: 91%

Section: Mo-u Relationshipcontrasting

confidence: 72%

Section: Mo-u Relationshipmentioning

confidence: 99%

Section: Mo-u Relationshipmentioning

confidence: 99%

See 2 more Smart Citations

Redox conditions in a coastal zone of the Humboldt system (Mejillones, 23° S). Influence on the preservation of redox-sensitive metals

Valdés

Sifeddine

Boussafir

et al. 2014

Journal of Geochemical Exploration

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show abstract

“…The major source of Mo to the ocean is oxidative weathering of crustal sulfides and black shales (Bertine and Turekian, 1973). The largest modern oceanic sink for Mo is co-precipitation and adsorption with Mn-oxyhydroxides in oxic environments (Barling et al, 2001;McManus et al, 2006;Siebert et al, 2003). However, the behavior of Mo depends strongly on redox conditions.…”

Section: Molybdenum Geochemistrymentioning

confidence: 99%

Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

Wang

Struck

Guo

et al. 2015

Precambrian Research

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Carbon cycling and burial in New Zealand's fjords

Hinojosa

Moy

Stirling

et al. 2014

Geochem. Geophys. Geosyst.

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Understanding carbon cycling in continental margin settings is critical for constraining the global carbon cycle. Here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six New Zealand fjords. Using carbon and nitrogen concentrations and isotopes, lipid biomarkers, and redoxsensitive element concentrations, we show that the New Zealand fjords have carbon-rich surface sediments in basins that promote long-term storage (i.e., semirestricted basins with sediment accumulation rates of up to 4 mm yr 21 ). Using d 13 C distributions to develop a mixing model, we find that organic carbon in fjord sediments is well-mixed from marine and terrestrial sources in down-fjord gradients. This is driven by high regional precipitation rates of >6 m yr 21 , which promote carbon accumulation in fjord basins through terrestrial runoff. In addition, we have identified at least two euxinic subbasins, based on uranium, molybdenum, iron, and cadmium enrichment, that contain >7% organic carbon. Because the strength and position of the Southern Hemisphere westerly winds control precipitation and fjord circulation, carbon delivery and storage in the region are intimately linked to westerly wind variability. We estimate that the fjord region (759 km 2 ) may be exporting up to 1.4 3 10 7 kgC yr 21 , outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude.

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Molybdenum and uranium geochemistry in continental margin sediments: Paleoproxy potential

Cited by 325 publications

References 112 publications

Redox conditions in a coastal zone of the Humboldt system (Mejillones, 23° S). Influence on the preservation of redox-sensitive metals

Redox conditions in a coastal zone of the Humboldt system (Mejillones, 23° S). Influence on the preservation of redox-sensitive metals

Marine redox variations and nitrogen cycle of the early Cambrian southern margin of the Yangtze Platform, South China: Evidence from nitrogen and organic carbon isotopes

Carbon cycling and burial in New Zealand's fjords

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