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Registros recuperados: 59
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Palynomorphs in Holocene sediments from a paleolagoon in the coastal plain of extreme southern Brazil Acta Botanica
Masetto,Ebráilon; Lorscheitter,Maria Luisa.
This paper presents the results of a qualitative palynological analysis of a 140 cm-thick section of Holocene sediments from a paleolagoon, representing the last 2600 years, taken from an outcrop at Hermenegildo Beach (33º42'S; 53º18'W), located in the municipality of Santa Vitória do Palmar, in the state of Rio Grande do Sul, Brazil. Samples were treated with hydrochloric acid, hydrofluoric acid and potassium hydroxide, after which they were subjected to acetolysis and mounted on glycerin-coated slides for light microscopy analysis. Among the 48 palynomorphs identified were 25 fungi, eight algae, three bryophytes, and 12 pteridophytes. Brief descriptions and illustrations of each palynomorph are presented, together with ecological data from the organism...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Palynomorph descriptions; Paleolagoon; Holocene; Southern coastal plain; Rio Grande do Sul.
Ano: 2014 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-33062014000200003
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Past and current sediment dispersion pattern estimates through numerical modeling of wave climate: an example of the Holocene delta of the Doce River, Espírito Santo, Brazil Anais da ABC (AABC)
Bittencourt,Abílio C.S.P.; Dominguez,José M.L.; Martin,Louis; Silva,Iracema R.; de-Medeiros,Karla O.P..
This paper presents a numerical modeling estimation of the sediment dispersion patterns caused by waves inciding through four distinct coastline contours of the delta plain of the Doce River during the Late Holocene. For this, a wave climate model based on the construction of wave refraction diagrams, as a function of current boundary conditions, was defined and was assumed to be valid for the four coastlines. The numerical modeling was carried out on basis of the refraction diagrams, taking into account the angle of approximation and the wave height along the coastline. The results are shown to be comparable with existing data regarding the directions of net longshore drift of sediments estimated from the integration of sediment cores, interpretation of...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Past and current sediment dispersion; Wave refraction; Numerical modeling; Holocene; Brazil.
Ano: 2007 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000200014
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Pollen analysis of Holocene sediments from the Poço das Antas National Biological Reserve, Silva Jardim, Rio de Janeiro, Brazil Anais da ABC (AABC)
Coelho,Luciane G.; Barth,Ortrud M.; Araujo,Dorothy S.D. de.
The Poço das Antas National Biological Reserve is located in Rio de Janeiro State, southeast Brazil. This paper presents information on past environmental characteristics of the area through pollen analysis. Two sedimentary columns were collected and five samples were selected for radiocarbon dating. The following ages of the columns from bottom to top were detected: column 1 - 1.20-1.16 m: 6080 ±40 years BP, 0.775-0.735 m: 4090 ±40 years BP, 0.385-0.345 m: 1880 ±80 years BP; column 2 - 1.22-1.18 m: 3520 ±40 years BP, 0.23-0.19 m: 1810 ±40 years BP. Three samples from column 1 and two samples from column 2 were selected for pollen analysis: 1.20 m, 0.77 m and 0.37 m of column1 and 1.22 m and 0.21 m of column 2. Chemical treatment followed standard...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Palynology; Paleo-environment; Holocene; Brazil.
Ano: 2008 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652008000300013
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Postglacial paleoceanography of the western Barents Sea: Implications for alkenone-based sea surface temperatures and primary productivity ArchiMer
Łącka, Magdalena; Cao, Min; Rosell-melé, Antoni; Pawłowska, Joanna; Kucharska, Małgorzata; Forwick, Matthias; Zajączkowski, Marek.
The increasing influence of Atlantic Water (AW) in the Barents Sea, a process known as “Atlantification”, is gradually decreasing sea ice cover in the region. Ongoing global climate warming is likely to be one of its drivers, but to further understand the role of natural variability and the biogeochemical impacts of the inflow of AW into the western Barents Sea, we reconstructed sea surface temperatures (SSTs) and primary productivity in Storfjordrenna, a climatically sensitive area south of Spitsbergen, between approximately 13,950 cal yr BP and 1300 cal yr BP. The alkenone proxy has been applied to reconstruct SSTs, and the alkenone accumulation rate in marine sediments has been used to infer changes in primary productivity. Our data show that the SST...
Tipo: Text Palavras-chave: Alkenones; Stratification; Holocene; Sea ice decrease; Global warming; North Atlantic Current; Arctic.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00585/69740/67629.pdf
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Post-glacial persistence of turbiditic activity within the Rhone deep-sea turbidite system (Gulf of Lions, Western Mediterranean): Linking the outer shelf and the basin sedimentary records ArchiMer
Dennielou, Bernard; Jallet, Laurent; Sultan, Nabil; Jouet, Gwenael; Giresse, Pierre; Voisset, Michel; Berne, Serge.
Emplacement of post-glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity. On the continental rise of the Gulf of Lions (Western Mediterranean), an aseismic area, we identified turbiditic beds deposited during the rising stage and highstand of sea level. Swath bathymetry, sediment cores, in situ Cone Penetrating Tests (CPTU), heavy mineral associations and radiocarbon dating determined the source, composition, distribution and age of the turbiditic beds. Turbidites are composed of homogeneous to positively graded silts to medium sand with quartz (up to 90%), shell debris and shelfal benthic faunas. Their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms. Their source is...
Tipo: Text Palavras-chave: Holocene; Late Pleistocene; Sea level; Turbidites; Sand; Outer shelf; Canyons.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6316.pdf
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Preliminary investigation on the Pleistocene/Holocene Sea-Level Changes along the Coastline of Tanzania, with reference to Unguja and Pemba Islands OceanDocs
Nyandwi, N.; Muzuka, A.N.N.; Shaghude, Y.W..
Along the coast of Tanzania, coral reefs, marine terraces and beach ridges are among the most important geomorphological features indicative of the Pleistocene/Holocene sea level changes. Three major terrace units can easily be identified on the mainland coast, namely, Mtoni (youngest), Tanga and Sakura (oldest). Three terrace units have also been identified on the Islands of Unguja and Pemba. On the basis of the difference in the terrace elevations between the two terrace systems it is postulated that the marine terraces on the islands probably represent minor fluctuations of sea level, rather than major phases of sea level fluctuation. A sand beach on the seaward side and several sand ridges on the landward side represent the Recent phase. The oldest...
Tipo: Report Palavras-chave: Geology; Pleistocene; Holocene.
Ano: 2003 URL: http://hdl.handle.net/1834/818
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Reconstitution de la variabilité naturelle climatique et océanographique dans l’estuaire et le golfe du Saint-Laurent au cours des 10,000 dernières années ArchiMer
Casse, Marie.
L’estuaire et le golfe du Saint-Laurent (EGSL, Est du Canada) sont des milieux très dynamiques d’un point de vue sédimentaire. Pourtant, les voies de propagation des sédiments fluviaux ainsi que l’origine et le mélange des apports sédimentaires en milieu marin ne sont pas bien documentés dans cette zone. Or, ces connaissances sont fondamentales pour déterminer les sources principales des apports terrigènes et mieux comprendre la dynamique de ce système sédimentaire. Dans ce contexte, les propriétés physiques, la distribution granulométrique, la minéralogie, les éléments majeurs et traces, et les isotopes radiogéniques (néodyme et strontium) d’un ensemble de sédiments de surface et de carottes sédimentaires de l’EGSL ont été étudiées dans cette thèse afin...
Tipo: Text Palavras-chave: Estuary and gulf of St.Lawrence; Holocene; Laurentide Ice Sheet; Relative sea level; Sedimentary dynamic; Mineralogy; Geochemistry; Radiogenic isotopes; Rare earth elements..
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00494/60611/64095.pdf
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Records of Holocene climatic fluctuations and anthropogenic lead input in elemental distribution and radiogenic isotopes (Nd and Pb) in sediments of the Gulf of Lions (Southern France) ArchiMer
Nizou, Jean; Dennielou, Bernard; Révillon, Sidonie; Bassetti, Maria-angela; Jouet, Gwenael; Berné, Serge; Nonnotte, Philippe; Liorzou, Celine.
Marine mud belts represent potential continuous high-resolution climatic, environmental and anthropogenic archives. In this study, a geochemical record of the Gulf of Lions mud belt, which receives sediments from the Rhône watershed and to a lesser extent from the Languedoc region, is reported from Core KSGC-31. The effects of natural climatic changes and possible anthropogenic disturbances on Holocene sedimentation were ascertained by analysing sedimentation rates, chemical weathering (Al2O3/K2O) and sediment-source shifts (neodymium isotopic ratios; εNd). Measurements of elemental and isotopic lead were used to trace the source and determine the potential vectors of anthropogenic contaminations over the Holocene. High εNd values, recorded from 9000 to...
Tipo: Text Palavras-chave: Holocene; Marine mud belt; Medieval lead contamination; Roman lead contamination; Sediment source fingerprinting; South of France.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00498/60951/68284.pdf
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Sea-level fluctuations and coastal evolution in the state of Rio de Janeiro, southeastern Brazil Anais da ABC (AABC)
CASTRO,JOÃO WAGNER A.; SUGUIO,KENITIRO; SEOANE,JOSÉ C.S.; CUNHA,ALINE M. DA; DIAS,FABIO F..
The present paper aims to investigate the relative sea-level and the coastal evolution during the Holocene in the Rio de Janeiro coastline, based on geological and biological indicators. Using topographic survey, excavation and coring, and 14C dating of these coastal deposits and beachrocks outcrops, we have reconstructed a sea-level curve for the Holocene. For the first time on the Brazilian coast it was identified a negative record of relative sea-level during Late Pleistocene and Early Holocene transition. After the transition, a relatively rapid increase of sea-level began. At approximately at 8500 cal yr BP, the sea-level was 0.5 m below the current level, was overtaken for the first time in the Holocene, at approximately 7500 cal yr BP. The maximum...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Sea-level fluctuations; Coastal evolution; Holocene; Brazilian coast.
Ano: 2014 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000200671
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Seasonal and subseasonal climate changes recorded in laminated diatom ooze sediments, Adelie Land, East Antarctica ArchiMer
Denis, Delphine; Crosta, X; Zaragosi, S; Romero, O; Martin, B; Mas, Virginie.
A 40 m long sediment core covering the 1000-9600 years BP period was retrieved from the Dumont d'Urville Trough off Adelie Land, East Antarctica, during the MD 130-Images X-CADO cruise. This sedimentary sequence allows the documentation of changes in climate seasonality during the Holocene. Here we show preliminary results of diatom communities, lithic grain distribution and titanium content measured on two 30 cm long sequences of thin sections. The two sequences originate from two different climate regimes, the colder Neoglacial and the warmer Hypsithermal. Proxies were measured at microscale resolution on 25 laminations for the Neoglacial and 14 laminations for the Hypsithermal. The two sequences reveal alternating light-green and dark-green laminae....
Tipo: Text Palavras-chave: East Antarctica; Sea ice; Seasonality; Diatom ooze; Laminated sediments; Holocene; Adelie Land.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/publication-2275.pdf
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Taphonomy of Bouchardia rosea (Rhynchonelliformea, Brachiopoda) shells from Ubatuba Bay, Brazil: implications for the use of taphonomic signatures in (paleo)environmental analysis Ameghiniana
Rodrigues,Sabrina Coelho; Simões,Marcello Guimarães.
This study analyzes taphonomic alteration of brachiopod shells, i.e., Bouchardia rosea (Mawe) from Ubatuba Bay, northern coast of São Paulo State, Brazil. The average age of the studied shell deposits is 674 years BP. The underlying hypothesis is that taphonomic signatures are not uniformly distributed along a bathymetric gradient. Assemblages were sampled using a Van Veen grab sampler (31 x 40cm) along transect of fourteen stations from zero (beach) to 35 m water depth. Four sedimentary environments were recognized: (a) beach, (b) protected bay with clay bottom, (c) protected bay with sandy bottom, and (d) inner shelf with sandy bottom. All brachiopod shells (i.e., total fraction including fragments) from each of the five stations with appreciable...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Bouchardia rosea; Brachiopods; Taphonomic signatures; Shell texture; Ubatuba Bay; Holocene.
Ano: 2010 URL: http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0002-70142010000300008
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Taxonomic revision of the recent and Holocene representatives of the Family Darwinulidae (Crustacea, Ostracoda), with a description of three new genera OMA
Rossetti, G.; Martens, K..
The Darwinulidae, the only surviving family of the superfamily Darwinuloidea, are revised and 28 extant species are retained. Twenty-six species (2 of which as yet formally undescribed) are allocated to 5 genera, 3 of which are here described as new; 2 species have an uncertain position within the family because of their insufficient original description are listed here as <i>species inquirendae</i>. New genera are characterised on combinations of soft part and valve characters, but the chaetotaxy of the limbs seems most conservative and most suitable the identification of genera. <i>Darwinula</i> s.s. and <i>Microdarwinula</i> are, with regard to recent species, monospecific.<i>Alicenula</i> nov. gen. is...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Animal fossils; Holocene; New genera; Phylogeny; Taxonomy; Alicenula; Darwinulidae; Ostracoda; Penthesilenula; Vestalenula.
Ano: 1998 URL: http://www.vliz.be/imisdocs/publications/266663.pdf
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The Dasypodidae (Mammalia, Xenarthra) from the Urso Fóssil Cave (Quaternary), Parque Nacional de Ubajara, State of Ceará, Brazil: paleoecological and taxonomic aspects Anais da ABC (AABC)
OLIVEIRA,PAULO V.; RIBEIRO,ANA MARIA; OLIVEIRA,ÉDISON V.; VIANA,MARIA SOMÁLIA S..
This paper deals with xenarthrans osteoderms assigned toDasypus aff. D. novemcinctus,Euphractus sexcinctus and Cabassous sp. The material was collected in subsurface, from 0.10 to 0.60 m in the Urso Fóssil Cave, Parque Nacional de Ubajara, State of Ceará, northeastern Brazil. The ages of sediment samples from levels 4 and 5 (depths of 0.40 and 0.50 m) were determined by thermoluminescence technique, and indicated ages of 8,000 and 8,200 years BP for each layer respectively. The presence in these layers of early Holocene xenarthrans taxa can contribute to the understanding of the biotic evolution of the northwest region of Ceará during the last 10,000 years. Two of the three identified taxa still occur in the region: Dasypus novemcinctus andEuphractus...
Tipo: Info:eu-repo/semantics/article Palavras-chave: Mammals; Dasypodidae; Holocene; Cave; Parque Nacional de Ubajara; Northeastern Brazil.
Ano: 2014 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652014000100147
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The experimental analysis on the Late Quaternary deposits of the Black Sea ArchiMer
Tekiroglu, Selin Eda; Ediger, Vedat; Yemenicioglu, Semal; Kapur, Selim; Akca, Erhan.
Holocene sediments taken from the south-eastern and western Black Sea have been investigated in relation to their geochemical, sedimentological and mineralogical characteristics. Their textures are characterized by their low amount of sand, upward-increasing silt and downward-increasing clay contents. While the terrigenous materials transported from Anatolian volcanic-based sources and European alluvial sediments form the shore deposits, the deep-sea sediments mainly consist of the marine biological production. The highest amount of organic carbon was deposited following the formation of anoxic conditions at the bottom until the beginning of the still continuing carbonate-rich coccolith (Emiliania huxleyi) deposition. The high metal concentrations are...
Tipo: Text Palavras-chave: Mer Noire; Holocène; Sapropel; Coccolithes; Black Sea; Holocene; Sapropel; Coccolith.
Ano: 2001 URL: http://archimer.ifremer.fr/doc/00323/43369/42841.pdf
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The last glacial maximum ans deglaciation in central Patagonia, 44°S-49°S ArchiMer
Mendelova, M.; Hein, A. S.; Mcculloch, R.; Davies, B..
This paper reviews published geochronological data on glacier fluctuations and environmental changes in central Patagonia (44 degrees S-49 degrees S) from the Last Glacial Maximum (LGM) through to the Holocene. Well-dated glacial chronologies from the southern mid-latitudes can inform on the synchronicity of glacial advances worldwide and provide insight on the drivers of southern hemisphere glaciations. In central Patagonia, two large outlet lobes of the former Patagonian Ice Sheet advanced in broad synchrony with the global LGM. In contrast to other parts of Patagonia, there is no convincing evidence for a more extensive local LGM advance during Marine Isotope Stage 3. Deglaciation initiated at ca. 19 ka, earlier than in other parts of Patagonia and...
Tipo: Text Palavras-chave: Last Glacial Maximum; Deglaciation; Holocene; Patagonia; Glacial chronology.
Ano: 2017 URL: https://archimer.ifremer.fr/doc/00497/60830/64500.pdf
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The mighty Susquehanna-extreme floods in Eastern North America during the past two millennia ArchiMer
Toomey, Michael; Cantwell, Meagan; Colman, Steven; Cronin, Thomas; Donnelly, Jeffrey; Giosan, Liviu; Heil, Clifford; Korty, Robert; Marot, Marci; Willard, Debra.
The hazards posed by infrequent major floods to communities along the Susquehanna River and the ecological health of Chesapeake Bay remain largely unconstrained due to the short length of streamgage records. Here we develop a history of high‐flow events on the Susquehanna River during the late Holocene from flood deposits contained in MD99‐2209, a sediment core recovered in 26 m of water from Chesapeake Bay near Annapolis, Maryland, USA. We identify coarse‐grained deposits left by Hurricane Agnes (1972) and the Great Flood of 1936, as well as during three intervals that predate instrumental flood records (~1800‐1500, 1300‐1100 and 400‐0 CE). Comparison to sedimentary proxy data (pollen and ostracode Mg/Ca ratios) from the same core site indicate that...
Tipo: Text Palavras-chave: Hurricane; Flood; Holocene; East coast; River; Chesapeake.
Ano: 2019 URL: https://archimer.ifremer.fr/doc/00483/59447/62291.pdf
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The rise and fall of the Refugial Hypothesis of Amazonian speciation: a paleoecological perspective Biota Neotropica
Bush,Mark B.; Oliveira,Paulo E. de.
The refugial hypothesis is treated as the definitive history of Amazonian forests in many texts. Surprisingly, this important theoretical framework has not been based on paleoecological data. Consequently, a model of Amazonian aridity during the northern hemispheric glaciation has been accepted uncritically. Ironically, the Refuge Hypothesis has not been tested by paleobotanical data. We present a revision of the concept of Neotropical Pleistocene Forest Refuges and test it in the light of paleocological studies derived from pollen analysis of Amazonian lake sediments deposited during the last 20,000 years. Our analysis is based primarily on paleoenvironmental data obtained from sites in Brazil and Ecuador. These data are contrasted with those that favor...
Tipo: Info:eu-repo/semantics/other Palavras-chave: Amazonia; Refugia; Fossil pollen; Glaciations; Pleistocene; Holocene; Miocene; Phylogeny; Speciation diversity.
Ano: 2006 URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1676-06032006000100002
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The timing and evolution of the post-glacial transgression across the Sea of Marmara shelf south of Istanbul ArchiMer
Eris, K; Ryan, W; Cagatay, M; Sancar, U; Lericolais, Gilles; Menot, G; Bard, E.
High-resolution reflection seismic profiles with core analyses of sedimentary sequence near the Sea of Marmara (SoM) entrance to the Strait of İstanbul (SoI, Bosphorus) provide detailed record of sealevel changes since the Late Glacial Maximum (LGM). The sequence is deposited over the LGM erosional surface at a maximum depth of -105 m. It includes seven seismic units that can be confidently correlated with 14C-dated sedimentary units in the cores. Unit 6 represents levee deposits of the paleo-SoI channel that was deposited by a Black Sea outflow during 11.2-10.6 kyr BP. The reflection surfaces at base of Unit 5 and 4 correspond to wave-cut terraces at -71and -63 m, respectively, and are estimated to be 10.6 and 9.8 kyr BP. The seismic Unit 2, overlaying a...
Tipo: Text Palavras-chave: Sapropel; Delta; Marmara Sea; Holocene; Sea level; Seismic stratigraphy.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3574.pdf
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Turbidite chronostratigraphy off Algiers, central Algerian margin: A key for reconstructing Holocene paleo-earthquake cycles ArchiMer
Babonneau, Nathalie; Cattaneo, Antonio; Ratzov, Gueorgui; Deverchere, Jacques; Yelles-chaouche, Abdelkarim; Lateb, Tassadit; Bachir, Roza Si.
Northern Algeria is threatened by moderate to large magnitude earthquakes resulting from the slow convergence between the African and European plates. Main active faults are located offshore along the Algerian coast, as exemplified by the 2003 Mw 6.9 Boumerdès earthquake. This event triggered numerous and widespread turbidity currents over ∼ 150 km along strike in the Algerian basin (reaching 2800 m of water depth) and demonstrates the multi-source and multi-path characteristics of earthquake-triggered turbidity flows along this margin segment. We rely on the sedimentological analysis of five cores located at the toe of the Algiers margin, close to the 2003 cable break sites, to explore the potential for Holocene turbidite paleoseismology. Radiocarbon...
Tipo: Text Palavras-chave: Algerian margin; Marine paleoseismology; Turbidite; Holocene.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00356/46701/46563.pdf
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