Consulta: subjectFacets:"Carbonates"
Registros recuperados: 13
Data/hora: 06/06/2024 10:35:38

Hydrodynamic behaviour of Nummulites: implications for depositional models
Provedor de dados: 5
Autores: Jorry, Stephan; Hasler, Ca; Davaud, E.
Large benthic foraminifers are considered to be good indicators of shallow marine carbonate environments in fossil series. Over the last 50 years, the palaeoenvironment of Tertiary Nummulites accumulations has been a matter of debate, particularly because of difficulties in interpreting these deposits, and in this way, the absence of analogues in present-day seas does not help. The aim of this paper is to insight the different ways Nummulites tests and clasts may accumulate according to their hydrodynamic behaviour. Based on experimental measurements and on SEM observations, it appears that the high primary skeletal porosity of Nummulites made them easily transportable. The calculated threshold shear velocities confirm that large-sized Nummulites can be...
Tipo: Text
Palavras-chave: Carbonates; Eocene; Large benthic foraminifera; Test density; Taphocoenosis.
Ano: 2006
URL: http://archimer.ifremer.fr/doc/00085/19597/17234.pdf

Lateglacial climate change and chronology at Lurga, western Ireland - derived from multiproxy and microtephra analysis -
Provedor de dados: 5
Autores: Duijkers, Mch.
Tipo: Text
Palavras-chave: Palaeoclimatology; Tephra; LOI; Isotope analysis; Carbonates; Lateglacial; Climate reconstruction; Calcareous gyttja.
Ano: 2009
URL: https://archimer.ifremer.fr/doc/00499/61044/64451.pdf

Investigation on the geochemical dynamics of a hydrate-bearing pockmark in the Niger Delta
Provedor de dados: 5
Autores: Ruffine, Livio; Caprais, Jean-claude; Bayon, Germain; Riboulot, Vincent; Donval, Jean-pierre; Etoubleau, Joel; Birot, Dominique; Pignet, Patricia; Rongemaille, Emmanuelle; Chazallon, Bertrand; Grimaud, Sylvie; Adamy, Jerome; Charlou, Jean-luc; Voisset, Michel.
A joint industrial project with IFREMER and Total provides insights into the tectonic setting and the geochemistry of a large active pockmark offshore W-Africa in the Niger Delta. The study combines both geophysical (seismic) and geochemical data to infer the dynamics of a 300 m wide pockmark located at 667 m water depth. Two Calypso cores, one at the centre and one outside the pockmark, along with three box-cores, two inside the pockmark and one outside, were collected to study the geochemistry of gas hydrates, carbonates and pore waters. Two seismic lines, a 3D high resolution random line and a 2D high resolution seismic line, provide a good description of the plumbing of the system. The integrated results depict a very active pockmark characterized by...
Tipo: Text
Palavras-chave: Active pockmark; Anaerobic oxidation of methane; Gas hydrates; Carbonates; Seismic surveys; Fault system; U/Th dating.
Ano: 2013
URL: http://archimer.ifremer.fr/doc/00139/24981/23102.pdf

Etude des vases et des biodépöts de Marennes-Oléron. Caractéristiques sédimentologiques
Provedor de dados: 5
Autores: CREOCEAN; IFREMER, Laboratoire LABEIM La Tremblade.
La présente étude est réalisée afin de préciser les caractéristiques des sédiments du bassin de Marennes-Oléron.
Tipo: Text
Palavras-chave: Sédiment; Vases; Caractéristiques; Teneur en eau; Carbonates; Matières organiques totales; Granulométrie; Bassin de Marennes Oléron.
Ano: 1991
URL: http://archimer.ifremer.fr/doc/00135/24631/22659.pdf

Les carbonates associés à la macrofaune des sables fins littoraux en Méditerranée nord-occidentale
Provedor de dados: 5
Autores: Masse, Hl.
The carbonates associated with the macrofauna of shallow fine sands have been evaluated at six stations located at five different sites on the French Mediterranean coast. The carbonate content of forty species or zoological groups has been estimated. At each station the mean calcimass has been calculated during a year-long cycle, showing the participation of the different zoological groups, mainly molluscs and echinoderms. The comparison of calcimass and associated biomass shows that CaCO3/AFDW ratio fluctuates between 1.6 to 19.3. These values are similar to those obtained in some rocky bottom communities. Calcimass values usually largely exceed biomass ones; therefore the carbon linked to carbonates cannot be excluded from the carbon balance including...
Tipo: Text
Palavras-chave: Carbonates; Macrofaune; Sables fins littoraux tempérés; Carbonates; Macrofauna; Temperate shallow fine sands.
Ano: 1999
URL: http://archimer.ifremer.fr/doc/00325/43604/43923.pdf

The old, unique C1 chondrite Flensburg - Insight into the first processes of aqueous alteration, brecciation, and the diversity of water-bearing parent bodies and lithologies
Provedor de dados: 5
Autores: Bischoff, Addi; Alexander, Conel M. O'D; Barrat, Jean-alix; Burkhardt, Christoph; Busemann, Henner; Degering, Detlev; Di Rocco, Tommaso; Fischer, Meike; Fockenberg, Thomas; Foustoukos, Dionysis, I; Gattacceca, Jerome; Godinho, Jose R. A.; Harries, Dennis; Heinlein, Dieter; Hellmann, Jan L.; Hertkorn, Norbert; Holm, Anja; Jull, A. J. Timothy; Kerraouch, Imene; King, Ashley J.; Kleine, Thorsten; Koll, Dominik; Lachner, Johannes; Ludwig, Thomas; Merchel, Silke; Mertens, Cornelia A. K.; Morino, Precillia; Neumann, Wladimir; Pack, Andreas; Patzek, Markus; Pavetich, Stefan; Reitze, Maximilian P.; Rufenacht, Miriam; Rugel, Georg; Schmidt, Charlotte; Schmitt-kopplin, Philippe; Schonbachler, Maria; Trieloff, Mario; Wallner, Anton; Wimmer, Karl; Woelfer, Elias.
On September 12, 2019 at 12:49:48 (UT) a bolide was observed by hundreds of eye-witnesses from the Netherlands, Germany, Belgium, Denmark and the UK. One day later a small meteorite stone was found by accident in Flensburg. The presence of short-lived cosmogenic radionuclides with half-lives as short as 16 days proves the recent exposure of the found object to cosmic rays in space linking it clearly to the bolide event. An exceptionally short exposure time of similar to 5000 years was determined. The 24.5 g stone has a fresh black fusion crust, a low density of &lt;2 g/cm(3), and a magnetic susceptibility of log chi = 4.35 (chi in 10(-9) m(3)/kg). The rock consists of relict chondrules and clusters of sulfide and magnetite grains set in a fine-grained...
Tipo: Text
Palavras-chave: C1 chondrite; Carbonaceous chondrite; Aqueous alteration; Carbonates; Early solar system; Oldest carbonates in solar system; Unique chondrite; Ungrouped C chondrite.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00686/79845/82672.pdf

Fluid seepage in relation to seabed deformation on the central Nile Deep-Sea Fan, part 2: evidence from multibeam and sidescan imagery
Provedor de dados: 5
Autores: Praeg, Daniel; Ketzer, Joao Marcelo; Augustin, Adolfo Herbert; Migeon, Sebastien; Ceramicola, Silvia; Dano, Alexandre; Ducassou, Emmanuelle; Dupre, Stephanie; Mascle, Jean; Rodrigues, Luiz Frederico.
On the central Nile deep-sea fan, stratified sediments overlying mass-transport deposits (MTDs) are deformed into slope-parallel seabed undulations associated with fluid seepage. The western part of this system, in water depths of 1,950–2,250 m, is examined using multi-frequency data from hull-mounted and deep-towed swath/profiling systems. Sub-bottom profiles show sub-vertical fluid pipes that terminate both at and below seabed, and gas signatures along fault planes bounding the undulations. Fluid seepage is recorded by high- to intermediate-backscatter patches (HBPs, IBPs) that differ in appearance on multibeam imagery (30 kHz, ≤3 m penetration) and sidescan swaths (170/190 kHz, &lt;0.1 m penetration). Comparison of the two suggests a distinction of (a)...
Tipo: Text
Palavras-chave: Slope undulations; Fluid seeps; Backscatter; Carbonates; Pipes; Faults.
Ano: 2014
URL: http://archimer.ifremer.fr/doc/00158/26956/25251.pdf

Composition des isotopes stables du molybdène dans les carbonates du Précambrien : affinement du proxy et applications paléo-environnementales
Provedor de dados: 5
Autores: Thoby, Mary.
The redox conditions of the oceans evolved considerably during the Precambrian. This is mainly due to the arrival of the oxygen, at first generating oxygen oases, and then accumulating in the atmosphere during the Great Oxidation Event (GOE) ca. 2.45 Ga. However, the earliest traces of free oxygen during these periods, and the mechanisms of their sedimentary expression, remain poorly understood. For over a decade, the isotopic composition of molybdenum (δ98Mo) in sediments has been used as a global marine redox proxy.An elemental and isotopic study of the different phases constituting carbonate rocks was carried out using sequential digestions performed on carbonates of different ages and depositional environments. The results show that Mo is primarily...
Tipo: Text
Palavras-chave: Redox; Précambrien; Carbonates; Molybdène; Isotopes; Attaque séquentielle; Sequential digestion; Precambrian; Molybdenum.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00663/77462/79129.pdf

Transferts sédimentaires sur une marge carbonatée moderne de la plate-forme à la plaine abyssale : marge nord de Little Bahama Bank, Bahamas
Provedor de dados: 5
Autores: Fauquembergue, Kelly.
Over the past decade, the Little Bahamas Bank (LBB) in the Caribbean has been at the heart of oceanographic cruises Carambar (2010), Caramba 1.5 (2014) and Carambar 2 (2016-2017). These scientific expeditions were carried out with the aim of improving our knowledge of the processes that controlled sediment export during the Quaternary in this tropical setting. Thus, bathymetric data covering some 24,270 km² of seabed, high-resolution seismic lines running over 6,398 km and 42 sediment cores ranging from 177 to 4,873 m water depth were collected in the upper slope through to the abyssal plane of the LBB system. This study focusses on those sediment cores retrieved in the upper (Carambar 1.5) and lower slope of the LBB and those from the Great Canyon...
Tipo: Text
Palavras-chave: Bahamas; Pente; Cabonates; Ouragans; Fronts froids; Bahamas; Slope; Carbonates; Hurricanes; Cold Fronts.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00684/79601/82297.pdf

Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process
Provedor de dados: 109
Autores: Chaparro-Acuña,Sandra Patricia; Becerra-Jiménez,Mónica Liliana; Martínez-Zambrano,José Jobanny; Rojas-Sarmiento,Hugo Alfonso.
Abstract Bacteria with ureasic activity are microorganisms found in soil that in presence of urea and calcium, they can produce calcium carbonate, a process known as microbiologically induced calcium carbonate precipitation (MICP). This article discusses this process and its mechanism, as well as bacterial urease, calcium carbonate crystals formed, and factors that affect the efficiency of MICP, as type of bacteria, bacterial cell concentrations, pH, temperature and calcium and urea concentrations. In addition, applications as removal of heavy metals in water, bioconsolidation, biocement and CO2 sequestration are also discussed.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Biomineralization; Bacillus; Urease; Carbonates; Heavy metals; Bioconsolidation; Biocementation.
Ano: 2018
URL: http://www.scielo.org.co/scielo.php?script=sci_arttext&pid=S0120-28122018000200277

Characteristics, distribution and diagenetic stages of chert in the La Silla Formation (Lower Ordovician), Argentine Precordillera
Provedor de dados: 42
Autores: 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

C-, Sr-isotope stratigraphy of carbonate rocks from the Southern Espinhaço Ridge, Minas Gerais, southeastern Brazil
Provedor de dados: 42
Autores: FRAGA,LUCIO M.S.; NEVES,SORAYA C.; UHLEIN,ALEXANDRE; SIAL,ALCIDES N.; PIMENTEL,MARCIO M.; HORN,ADOLF H.
Neoproterozoic carbonate rocks comprise different stratigraphic units in the southern part of the Espinhaço Ridge, Minas Gerais, Brazil. C, O- and Sr-isotope analyses were carried out along four selected stratigraphic sections across these formations. These are: (i) the Rio Pardo Grande Formation in the upper portion of the Espinhaço Supergroup, sampled in section 3; (ii) Macaúbas Group laminated limestones (Tijucuçu Farm) and dolostone layers (Domingas Formation) have been respectively sampled along the so-called sections 1 and 2, and (iii) the lower stratigraphic units of the Bambuí Group, sampled in section 4. Laminated limestone samples from the Macaúbas Group have δ13C values as high as 10.9‰ decreasing up section to -1.1‰ and 87Sr/86Sr values vary...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Sr isotopes; C isotopes; Carbonates; Macaúbas Group; Bambuí Group; Marinoan glaciation.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000200633

Carbon isotope fluctuations in Precambrian carbonate sequences of several localities in Brazil
Provedor de dados: 42
Autores: SIAL,ALCIDES N.; FERREIRA,VALDEREZ P.; DEALMEIDA,AFONSO R.; ROMANO,ANTONIO W.; PARENTE,CLOVIS V.; DACOSTA,MARCONDES L.; SANTOS,VICTOR H.
Carbon isotope fluctuations in Precambrian sedimentary carbonates between 2.8 Ga and 0.60 Ga in Brazil are examined in this study. The carbonate facies of the BIF of the 2.8 Ga-old Carajás Formation, state of Pará in northern Brazil, has rather homogeneous delta13C (-5 o/ooPDB), compatible with carbonatization of a silicate protolith by a CO2-rich fluid from mantle degassing. The Paleoproterozoic Gandarela Formation, state of Minas Gerais, displays a narrow delta13C variation (-1.5 to +0.5 o/oo) compatible with carbon isotope signatures of carbonates deposited around 2.4 Ga worldwide. The Fecho do Funil Formation has probably recorded the Lomagundi delta13C positive anomaly (+6.4 to +7.1 o/ooPDB). The magnesite-bearing carbonates of the Orós mobile belt,...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Carbon isotopes; Carbonates; Chemostratigraphy; Archean; Paleoproterozoic; Neoproterozoic.
Ano: 2000
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652000000400006