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| Registros recuperados: 13 | |
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| Bouilloux, Alexandra; Valet, Jean-pierre; Bassinot, Franck; Joron, Jean-louis; Blanc-valleron, Marie-madeleine; Moreno, Eva; Dewilde, Fabien; Kars, Myriam; Lagroix, France. |
| Large changes in magnetic mineral concentration dependent parameters by more than 1 order of magnitude occur over 50-150 cm intervals in two marine sediment cores from the oxygen minimum zone in the Gulf of Aden. High-resolution sedimentological and chemical analyses indicate that these intervals are not associated with turbiditic events or sediment reworking, they do not result from changes in carbonate dilution or differences in sediment properties, and they do not correspond to volcanic layers. Magnetic mineralogical analyses reveal a change in magnetic mineral concentration from a magnetite-goethite assemblage to pure magnetite within the peak. The peaks almost disappear when the abundance of magnetic minerals is calculated after correcting for the... |
| Tipo: Text |
Palavras-chave: Paleomagnetism; Paleoenvironment; Goethite; Magnetite; Indian ocean. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37488/36828.pdf |
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| Wang, Wei-lung; Wang, Liang-chi. |
| This study provides insight into changes in sea ice conditions and the oceanographic environment over the past 500 kyr through analysis of the diatom record. Based on the relative abundance of 13 diatoms species in piston core MD012414, four types of environmental conditions in the central Okhotsk Sea over the last 330 ka BP have been distinguished: (1) open-ocean alternating with seasonal sea-ice cover in Stages 9, 5, and 1; (2) almost open-ocean free of sea-ice cover in Stages 7 and 3; (3) perennial sea-ice cover in Stages 6, 4, and 2; and (4) a warm ice-age dominated by open ocean assemblages in Stage 8. The littoral diatom species, Paralia sulcata, showed a sudden increase from the glacial period to the interglacial period over the last 330 ka BP,... |
| Tipo: Text |
Palavras-chave: Diatom indicator; Okhotsk Sea; Sea-ice; Paleoenvironment. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34819/33683.pdf |
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| Zhao, Xueqin. |
| South Africa is very sensitive to climate change, because it is located between two atmospheric systems (subtropical and warm-temperate systems) and two oceanic systems (Benguela Current and Agulhas Current). Presently, the seasonal changes of atmospheric and oceanic systems induce a pronounced rainfall seasonality comprised of three different rainfall zones (summer rainfall zone, SRZ; year-round rainfall zone, YRZ and winter rainfall zone, WRZ) over South Africa. However, the seasonality development during the Holocene in South Africa is poorly understood and the driving forces of the climate change are debated. Therefore, this study aims to provide a detailed reconstruction of Holocene climate and vegetation variability of South Africa,... |
| Tipo: Text |
Palavras-chave: Holocene; Marine sediments; Pollen; Microcharcoal; Organic-walled dinoflagellate cyst; Paleoenvironment; Paleoceanography; South Africa. |
| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00493/60442/63887.pdf |
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| Chauvaud, Laurent; Lorrain, Anne; Dunbar, Robert; Paulet, Yves; Thouzeau, Gérard; Jean, Frédéric; Guarini, Jean-marc; Mucciarone, David. |
| We investigate the environmental and biological controls on oxygen isotope ratios in the shells of modern Pecten maximus bivalves collected alive in the Bay of Brest (France). Seasonal delta(18)O profiles, obtained by drilling the daily calcite ridges deposited at the surface of the left valve, were compared with in situ measurements of temperature and salinity. We show that P. maximus delta(18)O values accurately track seasonal variations in bottom water temperature. Shell growth rate has no significant effect on shell delta(18)O values. Our study demonstrates that daily variations in water temperature can be reconstructed within about 0.5 degrees C. Temperatures estimated with the paleotemperature equation established in this study were compared with... |
| Tipo: Text |
Palavras-chave: Pecten Maximus; Brittany; Paleoenvironment; Estimation; Daily varition; Water temperature; Isotope; Calcite; Shell; Ëecten maximus; Paleotempérature; Variation saisonnière; Température eau; Strie croissance; Isotope; Coquille. |
| Ano: 2005 |
URL: http://archimer.ifremer.fr/doc/2005/publication-643.pdf |
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| Garrido,Alberto C.. |
| Outcrops of Anacleto Formation at Auca Mahuevo nesting site (Neuquén Province, Argentina) can be divided into two main sections. The lower section (51 m), exhibits a succession of point bar, levee, crevasse channel and crevasse splay deposits, typifing a fine-grained, mixed load, meandering fluvial system. Twenty five km toward south (Los Barreales locality) these deposits become progressively to distal floodplain facies. Egg-layers are exposed along this 25 km, however a higher concentration of egg-clutches occur into paleosols and abandoned channel deposits developed at ancient levee and meander belt areas. Lithofacial evidences allow attributing for this lower section semiarid climatic condition, with marked alternations of wet and dry seasons.... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Anacleto Formation; Upper Cretaceous; Neuquén Basin; Paleoenvironment; Dinosaur nesting-sites. |
| Ano: 2010 |
URL: http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0002-70142010000100007 |
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| Borromei,Ana M.; Quattrocchio,Mirta. |
| An early-middle Holocene section in Bahía Lapataia (54º 50' S, 68º 34' W), Beagle Channel, Tierra del Fuego, Argentina has been examined taking into account its sporomorphs and organic-walled microplankton. The palynological assemblage suggests nearshore environments. Two relatively higher sea levels were identified by the increased abundance of organic-walled dinoflagellate cysts (Brigantedinium spp., Selenopemphix sp., Operculodinium centrocarpum sensu Wall and Dale, Spiniferites spp.), the acritarch Halodinium sp. and zoomorph remains (test linings of foraminifera and copepod egg-envelopes). The littoral vegetation at the time of the marine incursion was mainly arboreal, as can be seen in the pollen records by significant increase in Nothofagus dombeyi... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Palynology; Paleoenvironment; Holocene transgression; Bahía Lapataia; Beagle Channel; Tierra del Fuego; Argentina. |
| Ano: 2007 |
URL: http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0002-70142007000100011 |
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| Barth,Ortrud M.; Barreto,Cíntia F.; Coelho,Luciane G.; Luz,Cynthia F.P.. |
| Pollen analysis of a sediment sample obtained at 222 cm from the top of a drilling core collected in the Bay of Guanabara, Rio de Janeiro, was used as a tool to obtain more knowledge about pre-historical human living and environment. 14C datation revealed the age of 4210 years B.P. Most frequent pollen grains came from plants like Alchornea (Euphorbiaceae), Celtis (Ulmaceae), Lecythidaceae, Meliaceae, Ochnaceae and spores from forest Pteridophyta. Palynology and environmental studies revealed that agricultural activities could not be detected. The dense tropical rain forest was the dominant vegetation occurring in this region. |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Pollen; Paleoenvironment; Guanabara Bay; Rio de Janeiro; 4210 BP. |
| Ano: 2004 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652004000300009 |
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| Barreto,Cintia F.; Luz,Cynthia F.P. da; Baptista-Neto,José A.; Vilela,Claudia G.; Barth,Ortrud M.. |
| The sediment of a core collected about 2 km north of Paquetá Island, Guanabara Bay, was submitted to pollen analysis, in order to recognize the dynamics of the regional vegetation, and the anthropic influence. Radiocarbon dating of a sample next to the bottom of the core indicates an age of 4.210 ± 40 14C yrs B.P (calibrated age). It was possible to establish four palynological zones. Starting at the bottom of the core, a decrease in palynomorph concentration, the presence of degraded pollen grains and spores, and the predominance of ombrophilous forest pollen grains were observed in the basal portion of Zone I. These data may indicate the presence of an exuberant Atlantic Forest, dominated by a marine regressive event. The concentration of well-preserved... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Pollen; Quaternary Palynology; Guanabara Bay; Paleoenvironment. |
| Ano: 2007 |
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652007000200005 |
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| Registros recuperados: 13 | |
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