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Carbonate cements in contemporaneous beachrocks, Jaguaribe beach, Itamaracá island, northeastern Brazil: petrographic, geochemical and isotopic aspects Anais da ABC (AABC)
Guerra,Núbia C.; Kiang,Chang H.; Sial,Alcides N..
Holocene beachrocks of the Jaguaribe beach, State of Pernambuco, northeastern Brazil, consist of horizontal, cemented layers approximately 40 cm thick. The cement shows three textural varieties: (a) calciferous, surrounding siliciclastic grains, (b) micritic, with an acicular fringe; and (c) cryptocrystalline calcite in pores. Early cementation took place at the water table below beach ridges, where geochemical, hydrodynamic and, perhaps, also microbiological conditions favored rapid precipitation of aragonite and/or high-Mg calcite. delta13C values range from -1.8 to +1.5‰ for dissolved carbonate in interstitial water and from +0.2 to +2.1‰ for bioclastic components. delta18O values range from -2.8 to +0.5‰ for seawater, freshwater and interstitial water....
Tipo: Info:eu-repo/semantics/article Palavras-chave: Beachrocks; Early diagenesis; O and C isotopes; Holocene.
Ano: 2005 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652005000200011
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Characteristics, distribution and diagenetic stages of chert in the La Silla Formation (Lower Ordovician), Argentine Precordillera Anais da ABC (AABC)
Raviolo,Mariana M.; Barbosa,José A.; Neumann,Virgínio H..
The late Cambrian - late Tremadocian La Silla Formation is a carbonate unit of the eastern Precordillera in Argentina whose facies indicate a shallow platform environment. Until this moment, there were no studies that referred to the diagenetic evolution of these rocks. The present study involves the characteristics and distribution of the silicification that affects this unit and determines its different diagenetic stages through petrographic (with cathodoluminescence support) and stratigraphic analyses. An early diagenetic chert, in a stage previous to the compactation, was observed. This chert is related to silica-rich seawater in contact with permeable and porous sediments. A later pulse of chert, associated with fracturing, also occurs. The knowledge...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Carbonates; Chert; Early diagenesis; Eastern Precordillera; Lower Ordovician.
Ano: 2009 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652009000400015
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Comportement du cadmium et du mercure lors de la diagenèse précoce et flux à l'interface eau-sédiments en zone littorale ArchiMer
Gonzalez, Jean-louis.
The early diagenesis of Cd and Hg has been studied in different coastal areas (vasière Ouest-Gironde, Pertuis d'Antioche, baie de Marennes-Oléron). For these two metals, the fluxes at the sediment-water interface have been calculated. Considering only molecular diffusion, the diffusionnal fluxes of Cd and Hg to the colurnn water are negligible with regard to both the particular fluxes to the sediments and the inputs of the "Gironde" and "Charente" ·,estuaries. The take into account of the different processes which affect the ex changes at the interface (erosion, bioturbation) permits more realistic an estimation of the role of sediments in the geochemical cycle of Cd and Hg. The results show that up to 50% of particular Cd and Hg which are integrated into...
Tipo: Text Palavras-chave: Cadmium; Mercure; Eaux intrstitielles; Diagenèse précoce; Flux; Interface eaux-sédiments; Bioturbation; Modélisation; Cadmium; Mercury; Pore waters; Early diagenesis; Fluxes; Sediment-water interface; Bioturbation; Modelling.
Ano: 1992 URL: http://archimer.ifremer.fr/doc/00442/55402/56920.pdf
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Effects of seasonal dynamics in a Zostera noltii meadow on phosphorus and iron cycles in a tidal mudflat (Arcachon Bay, France) ArchiMer
Deborde, Jonathan; Abrill, Gwenael; Mouret, Aurelia; Jezequel, Didier; Thouzeau, Gerard; Clavier, Jacques; Bachelet, Guy; Anschutz, Pierre.
A study was conducted in Arcachon Bay, France, to determine the effect of seasonal dynamics in a Zostera noltii meadow on P and Fe cycles in the superficial sediments of a tidal mudflat. The redox-sensitive Fe particulate pool and associated P in the root zone showed a seasonal variation following the growth and decay of Z. noltii biomass, with a maximum content during the growth period. In comparison, the bare sediments did not show significant seasonal changes. A dissolved inorganic phosphorus (DIP) uptake was measured from the water column to the sediment in vegetated sediments, whereas a net DIP efflux was observed in the unvegetated sediments. During the growth period, the formation of an iron oxihydroxide-rich zone occurred and acted as a trap for...
Tipo: Text Palavras-chave: Nutrient; Eelgrass growth; Intertidal zone; Lagoon; Early diagenesis.
Ano: 2008 URL: https://archimer.ifremer.fr/doc/00603/71539/69966.pdf
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Influence of early diagenesis on geotechnical properties of clay sediments (Romania, Black Sea) ArchiMer
Ballas, Gregory; Garziglia, Sebastien; Sultan, Nabil; Pelleter, Ewan; Toucanne, Samuel; Marsset, Tania; Riboulot, Vincent; Ker, Stephan.
The geotechnical properties of clay sediments were investigated using laboratory and in-situ measurements as part of the geohazard assessment in the Romanian sector of the Black Sea affected by landslides and seafloor deformation features. The sediments were characterized as predominantly high plastic silty clay of high compressibility, low undrained shear strength, low cohesion and moderate sensitivity. A shallow increase in shear strength exceeding the general trend could have been reconciled with evidence for the precipitation of iron sulfides and calcium carbonates related to early diagenetic reactions of sulfate reduction (e.g. cryptic sulfur cycle) and anaerobic oxidation of methane. Comparison of the compression behaviour of natural and...
Tipo: Text Palavras-chave: Lacustrine clay sediment; Structured material; Sulfur cement; Carbonate cement; Early diagenesis; Weak layer.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00439/55064/56545.pdf
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Strong gradient of benthic biogeochemical processes along a macrotidal temperate estuary: focus on P and Si cycles ArchiMer
Raimonet, Melanie; Andrieux, Francoise; Ragueneau, Olivier; Michaud, Emma; Kerouel, Roger; Philippon, Xavier; Nonent, Michel; Memery, Laurent.
Tipo: Text Palavras-chave: Early diagenesis; Silicate; Phosphate; Authigenic phosphorus; Macrotidal; Estuary.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00130/24115/22493.pdf
Registros recuperados: 6
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