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| Registros recuperados: 48 | |
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| Lyons, Richard; Tooth, Stephen; Duller, Geoff A. T.. |
| The nature, spatial patterns and forcing mechanisms of Quaternary climatic changes across southern Africa remain unresolved and contentious, principally due to the scarcity of continuous and robustly-dated proxy records. We present what we interpret to be a broadly continuous record of late Quaternary climatic change based on optically stimulated luminescence (OSL) dating, and mineral magnetic and diffuse reflectance spectroscopy (DRS) analyses of stacked palaeosols within an overbank alluvial succession along the Modder River, central South Africa. The OSL ages indicate that alluvial sedimentation occurred at a fairly steady rate, averaging similar to 0.15 mm/yr from at least 44 ka until similar to 0.83 ka. This suggests that the palaeosols are... |
| Tipo: Text |
Palavras-chave: Erfkroon; Southern Africa; Palaeosol; OSL; Quaternary; Mineral magnetism. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00290/40120/39120.pdf |
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| Pike, Jennifer; Crosta, Xavier; Maddison, Eleanor J.; Stickley, Catherine E.; Denis, Delphine; Barbara, Loic; Renssen, Hans. |
| The available ecological and palaeoecological information for two sea ice-related marine diatoms (Bacillariophyceae), Thalassiosira antarctica Comber and Porosira glacialis (Grunow) Jorgensen, suggests that these two species have similar sea surface temperature (SST), sea surface salinity (SSS) and sea ice proximity preferences. From phytoplankton observations, both are described as summer or autumn bloom species, commonly found in low SST waters associated with sea ice, although rarely within the ice. Both species form resting spores (RS) as irradiance decreases, SST falls and SSS increases in response to freezing ice in autumn. Recent work analysing late Quaternary seasonally laminated diatom ooze from coastal Antarctic sites has revealed that... |
| Tipo: Text |
Palavras-chave: East Antarctica; Quaternary; Diatoms; Sea ice. |
| Ano: 2009 |
URL: https://archimer.ifremer.fr/doc/00220/33092/82663.pdf |
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| Palm, Franziska A.; Peakall, Jeff; Hodgson, David M.; Marsset, Tania; Silva Jacinto, Ricardo; Dennielou, Bernard; Babonneau, Nathalie; Wright, Tim J.. |
| Submarine-fan channels can build the largest sediment accumulations on Earth, but our understanding of flow and sedimentation processes related to channel evolution remains limited. Results from physical and numerical modelling predict dominantly downstream channel bend migration. However, observations and evolutionary models for aggradational submarine channels on passive margins suggest that bends are dominated by lateral expansion. This paradox may be due to limitations induced by the use of constant width channels in process studies. Constant width has been used for two reasons: partly because this is the simplest possible case, but primarily because the width variation around submarine channel bends is unknown. Channel width variations are examined... |
| Tipo: Text |
Palavras-chave: Submarine channel; Congo; Channel morphology; Sedimentation; Bank pull; Quaternary; Monsoon; South Atlantic. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00693/80473/83602.pdf |
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| Schmitt, A.; Elliot, M.; Thirumalai, K.; La, C.; Bassinot, F.; Petersen, J.; Movellan, A.; Jorry, Stephan; Borgomano, J.. |
| The ratio of magnesium to calcium (Mg/Ca) in foraminiferal shells is commonly used as a proxy for past ocean temperature. Recent advances in elemental analyses now enable single-specimen measurements of planktic foraminifera and thus, can provide information on past seasonal and interannual variability, owing to the near-monthly lifespan of foraminifera. In this study, we explore the temperature variance recorded by Mg/Ca in tests of foraminifera Globigerinoides ruber, a planktic species that occurs throughout the year in tropical waters. Using LA-ICP-MS, we characterize Mg/Ca variability in single specimens of two morphotypes of G. ruber picked from a sediment core retrieved offshore New Caledonia. We provide an estimate of the range of calcification... |
| Tipo: Text |
Palavras-chave: Globigerinoides ruber; Mg/Ca ratio; Sea surface temperature; LA-ICPMS; Seasonality; Quaternary. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00472/58336/60890.pdf |
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| Xuan, Chuang; Channel, James E. T.; Hodell, David A.. |
| The sediment sequence from Integrated Ocean Drilling Program (IODP) Site U1304 (53 degrees 03.40'N, 33 degrees 31.78'W; water depth, 3024 m) on the southern Gardar Drift, North Atlantic Ocean, covers the last similar to 1.8 Myr with a mean sedimentation rate of similar to 15 cm/kyr. At Site U1304, paleomagnetic directional and relative paleointensity (RPI) records have been generated for the last similar to 1.5 Myr, and benthic oxygen isotope data for the last similar to 1 Myr. The age model for Site U1304 was established by matching 6180 and RPI data to calibrated reference records. Prominent intervals of diatom mats at Site U1304 are associated with the latter stages of interglacial marine isotope stages (MIS) 9, 11, 13, 15, 21, 27 and 35, and with the... |
| Tipo: Text |
Palavras-chave: Quaternary; North Atlantic; Relative paleointensity; Magnetic excursions; Oxygen isotopes; Diatoms; IODP Site U1304. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53238/83373.pdf |
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| Auffret, Gérard-andré; Zaragosi, S; Voisset, Michel; Droz, Laurence; Loubrieu, Benoit; Pelleau, Pascal; Savoye, R; Bourillet, Jean-francois; Baltzer, Agness; Bourquin, S; Dennielou, Bernard; Coutelle, Alain; Weber, N; Floch, Gilbert. |
| During the SEDIFAN 1 cruise we surveyed the bathymetry and the acoustic properties of the surface sediment of the Celtic Deep Sea Fan. We also collected Kullenberg cores in order to study recent sedimentary processes. From the bathymetry survey it is relatively easy to recognize the main areas of modern fan. The upper fan included a large sedimentary ridge which constitutes the right levee of the prominent meandering Whittard valley. After its confluence with the Shamrock valley the course of the Whittard valley is abruptly deflected to the south. At a short distance to the south the valley divides into two upper-fan channels, the Celtic channel to the west being the deeper one. This point constitutes the centre of a radiating pattern which is developed on... |
| Tipo: Text |
Palavras-chave: Paléoclimat; Turbidité; Sédiment; Quaternaire; Eventail profond; Palaeoclimate; Turbidity; Sediment; Quaternary; Deep sea fan. |
| Ano: 2000 |
URL: http://archimer.ifremer.fr/doc/2000/publication-525.pdf |
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| Chen, Chih-wei; Wei, Kuo-yen; Mii, Horng-sheng; Yang, Tien-nan. |
| A detailed oxygen isotope time-scale based on planktonic foraminifera Globigerinoides sacculifer at site MD012380 in the Banda Sea was established for the past 820 kyrs by correlating the record to the astronomically tuned benthic oxygen isotope chronology of MD972143. Ages for marine isotope stratigraphic (MIS) events from 2.0 back to 21.1 were designated for this western tropical Pacific record. Spectral analysis of the 6180 time-series reveals distinct periodicities of 100, 41, and 23 kyrs, indicating strong orbital forcing, yet the power of each band varies through time. The time-series of three other paleo-proxies, namely, coarse fraction (CF), lightness of sediments and delta C-13 of Globigerinoides saccidifer, were subjected to cross-spectral... |
| Tipo: Text |
Palavras-chave: Age model; Oxygen isotope stratigraphy; Quaternary; Banda Sea. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34814/33678.pdf |
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| Molliex, Stephane; Siame, Lionel L.; Bourles, Didier L.; Bellier, Olivier; Braucher, Regis; Clauzon, Georges. |
| Located in the foreland of the Western Alps, the Crau Plain was the outlet of the Durance River in the Pleistocene. In order to constrain its geodynamic evolution in terms of chronology and denudation rates, the two main Quaternary deposits of this plain have been studied based on cosmogenic nuclide Be-10 concentration measurements along depth profiles. The abandonment of the Miramas and Luquier alluvial surfaces occurred at the beginning of glacial periods, Wurm (isotopic stage 4) and Riss (isotopic stage 6), respectively. Discrepancy in denudation rates under similar geomorphological and lithological conditions suggests different denudation processes during glacial and interglacial periods. The denudation rate has been estimated at about 25 mm ka(-1) for... |
| Tipo: Text |
Palavras-chave: Quaternary; Denudation rate; Cosmic ray exposure (CRE) dating; Be-10 depth profile; Provence; Periglacial setting. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00149/26040/24740.pdf |
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| Van Nieuwenhove, Nicolas; Head, Martin J.; Limoges, Audrey; Pospelova, Vera; Mertens, Kenneth; Matthiessen, Jens; De Schepper, Stijn; De Vernal, Anne; Eynaud, Frédérique; Londeix, Laurent; Marret, Fabienne; Penaud, Aurélie; Radi, Taoufik; Rochon, André. |
| Organic-walled resting cysts of planktonic dinoflagellates occur commonly in modern marine sediment where they represent, with rare exceptions, the only geologically preservable part of the life cycle. Although many species do not produce fossilizable resting cysts, upper Quaternary sediments contain a diverse cyst record that is used frequently for paleoenvironmental reconstruction and stratigraphic analysis. Reconstructions of past sea-surface conditions rely on an understanding of the distributions of dinoflagellate cysts in modern sediments linked to their respective environmental parameters, underpinned by sound taxonomy and standardized nomenclature. Stratigraphic studies additionally require knowledge of morphological details to distinguish extant... |
| Tipo: Text |
Palavras-chave: Dinoflagellate cysts; Marine; Quaternary; Gymnodiniales; Gonyaulacales; Peridiniales. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00606/71817/70324.pdf |
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| Stuut, Jan‐berend W.; De Deckker, Patrick; Saavedra‐pellitero, Mariem; Bassinot, Franck; Drury, Anna‐joy; Walczak, Maureen H.; Nagashima, Kana; Murayama, Masafumi. |
| New proxy records from deep‐sea sediment cores from the northwestern continental margin of Western Australian reveal a 5.3 million‐year (Ma) history of aridity and tropical‐monsoon activity in northwestern Australia. Following the warm and dry early Pliocene (~5.3 Ma), the northwestern Australian continent experienced a gradual increase in humidity peaking at about 3.8 Ma with higher than present‐day rainfall. Between 3.8 and about 2.8 Ma, climate became progressively more arid with more rainfall variability. Coinciding with the onset of the northern hemisphere glaciations and the intensification of the northern hemisphere monsoon, aridity continued to increase overall from 2.8 Ma until today, with greater variance in precipitation and an increased... |
| Tipo: Text |
Palavras-chave: Paleoclimate; Monsoon; Australia; Runoff; Pliocene; Quaternary. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00502/61384/65035.pdf |
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| Ridente, D; Trincardi, F; Piva, A; Asioli, A; Cattaneo, Antonio. |
| [1] Borehole PRAD1-2 was drilled in similar to 186 m water depth on the upper slope of the central Adriatic, in the frame of Profiles across Mediterranean Sedimentary Systems (PROMESS1) European Union-funded project. The borehole penetrated 71.2 m through a stratigraphic interval characterized by subparallel seismic reflections and uniform seismic units. According to an age-depth model based on several independent proxies (including foraminifera and nannoplankton stratigraphy, delta O-18 curves, and magnetostratigraphy) the cored interval records Marine Isotope Stages and Substages (MIS) from MIS1 to the top of MIS11, thus encompassing the past similar to 370 ka. PRAD1-2 therefore represents an unprecedented continuous record through the last four... |
| Tipo: Text |
Palavras-chave: Adriatic Sea; Depositional sequences; High frequency climate cycles; Quaternary. |
| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-4759.pdf |
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| Berben, Sarah M.p.; Dokken, Trond M.; Abbott, Peter M.; Cook, Eliza; Sadatzki, Henrik; Simon, Margit H; Jansen, Eystein. |
| Understanding the dynamics that drove past abrupt climate changes, such as the Dansgaard-Oeschger (DO) events, depends on combined proxy evidence from disparate archives. To identify leads, lags and synchronicity between different climate system components, independent and robust chronologies are required. Cryptotephrochronology is a key geochronological tool as cryptotephra horizons can act as isochrons linking disparate and/or distant records. Here, we investigated marine sediment core MD99-2284 from the Norwegian Sea to look for previously identified Greenland ice core cryptotephra horizons and define time-parallel markers between the archives. We explored potential secondary transport and depositional mechanisms that could hamper the isochronous... |
| Tipo: Text |
Palavras-chave: Quaternary; Paleoclimatology; Paleoceanography; North Atlantic; Sedimentology; Marine cores; Ice cores; Cryptotephrochronology; DO-Events; Synchronization. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00622/73391/72606.pdf |
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| Schmidt, Matthew W.; Spero, Howard J.. |
| Paleoproxy studies show a strong correlation between tropical climate and high-latitude temperature variability recorded in the Greenland ice cores over the last glacial cycle. In particular, abrupt cooling events in the Greenland Ice Sheet Project II delta(18)O ice record appear synchronous with a southward migration of the Intertropical Convergence Zone (ITCZ) in the Atlantic, a weakening of the Indian and East Asian monsoon systems, and a strengthening of the South American monsoon system. Because this high-to-low-latitude climate teleconnection significantly alters the tropical hydrologic cycle around the globe, it plays a critical role in regulating global climate on glacial-interglacial time scales. We compare delta(18)O(seawater) reconstructions (a... |
| Tipo: Text |
Palavras-chave: Hydrologic cycle; Mg/Ca; Quaternary; Tropics; Salinity; ITCZ. |
| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00228/33877/32255.pdf |
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| Cheshire, Heather; Thurow, Juergen. |
| Guaymas Basin, Gulf of California, is a restricted basin located under the present-day wet/dry subtropical divide (similar to 27 degrees N) and is ideally circumstanced for detecting variations in the North Pacific Subtropical High (NPSH)/Trade Wind system. Controlled by climate cell boundary displacement, NPSH midwinter location was the primary influence on timing and intensity of upwelling seasons in Guaymas Basin. Analysis of high-resolution X-ray fluoresence data and sediment fabric log from 75% laminated Core MD02-2517/2515, western Guaymas Basin, reveals systematic changes in NPSH behavior over the last similar to 55 kyr BP. Southward displacement of the wet/dry subtropical divide controlled upwelling-related diatom productivity, while sea level and... |
| Tipo: Text |
Palavras-chave: Quaternary; Paleoceanography; X-ray fluorescence; Laminated sediment. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37527/35762.pdf |
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| Cabioch, G; Correge, T; Turpin, L; Castellaro, C; Recy, J. |
| In New Caledonia, core data indicate that the fringing reefs grew during the last interglacial and the Holocene, while the barrier reefs developed during several high sea level stands of the Quaternary. These growth periods are archived in a 128-m-long core from Ilot Amedee, offshore of Noumea. Directly upon the peridotitic substrate (reached at 126.50 m), a basal unit comprising abundant rhodoliths, molluscs and rare corals is characteristic of the pioneer stage of barrier reef development. Above it, a severely calcitized unit contains corals, molluscs and abundant micritic levels. Then, a sequence punctuated by several minor discontinuities and by a downward increase in diagenetic alteration is found. At 47 m core depth, a unit, which is thought to be... |
| Tipo: Text |
Palavras-chave: Croissance récifale; Néotectonique; Nouvelle-Calédonie; Quaternaire; Reef growth; Neotectonics; New Caledonia; Quaternary. |
| Ano: 1999 |
URL: http://archimer.ifremer.fr/doc/00325/43582/44021.pdf |
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| Registros recuperados: 48 | |
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