23 results on '"Vasiliki Margari"'
Search Results
2. A 1.5-million-year record of orbital and millennial climate variability in the North Atlantic
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David Hodell, Simon Crowhurst, Lucas Lourens, Vasiliki Margari, John Nicolson, James E. Rolfe, Luke C. Skinner, Nicola Thomas, Polychronis C. Tzedakis, Maryline J. Mleneck-Vautravers, Eric W. Wolff, Hodell, DA [0000-0001-8537-1588], Tzedakis, PC [0000-0001-6072-1166], Mleneck-Vautravers, MJ [0000-0003-2534-219X], Wolff, EW [0000-0002-5914-8531], Apollo - University of Cambridge Repository, Stratigraphy and paleontology, and Stratigraphy & paleontology
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Global and Planetary Change ,Scale changes ,Meridional overturning circulation ,Palaeontology ,Stratigraphy ,Paleontology ,37 Earth Sciences ,3705 Geology ,3709 Physical Geography and Environmental Geoscience ,Time scales ,Deep-water ,Bering strait ,Ocean circulation ,Persistent influence ,Southern-ocean ,Site u1385 ,Glacial terminations - Abstract
Climate during the last glacial period was marked by abrupt instability on millennial timescales that included large swings of temperature in and around Greenland (Daansgard–Oeschger events) and smaller, more gradual changes in Antarctica (AIM events). Less is known about the existence and nature of similar variability during older glacial periods, especially during the early Pleistocene when glacial cycles were dominantly occurring at 41 kyr intervals compared to the much longer and deeper glaciations of the more recent period. Here, we report a continuous millennially resolved record of stable isotopes of planktic and benthic foraminifera at IODP Site U1385 (the “Shackleton Site”) from the southwestern Iberian margin for the last 1.5 million years, which includes the Middle Pleistocene Transition (MPT). Our results demonstrate that millennial climate variability (MCV) was a persistent feature of glacial climate, both before and after the MPT. Prior to 1.2 Ma in the early Pleistocene, the amplitude of MCV was modulated by the 41 kyr obliquity cycle and increased when axial tilt dropped below 23.5∘ and benthic δ18O exceeded ∼3.8 ‰ (corrected to Uvigerina), indicating a threshold response to orbital forcing. Afterwards, MCV became focused mainly on the transitions into and out of glacial states (i.e. inceptions and terminations) and during times of intermediate ice volume. After 1.2 Ma, obliquity continued to play a role in modulating the amplitude of MCV, especially during times of glacial inceptions, which are always associated with declining obliquity. A non-linear role for obliquity is also indicated by the appearance of multiples (82, 123 kyr) and combination tones (28 kyr) of the 41 kyr cycle. Near the end of the MPT (∼0.65 Ma), obliquity modulation of MCV amplitude wanes as quasi-periodic 100 kyr and precession power increase, coinciding with the growth of oversized ice sheets on North America and the appearance of Heinrich layers in North Atlantic sediments. Whereas the planktic δ18O of Site U1385 shows a strong resemblance to Greenland temperature and atmospheric methane (i.e. Northern Hemisphere climate), millennial changes in benthic δ18O closely follow the temperature history of Antarctica for the past 800 kyr. The phasing of millennial planktic and benthic δ18O variation is similar to that observed for MIS 3 throughout much of the record, which has been suggested to mimic the signature of the bipolar seesaw – i.e. an interhemispheric asymmetry between the timing of cooling in Antarctica and warming in Greenland. The Iberian margin isotopic record suggests that bipolar asymmetry was a robust feature of interhemispheric glacial climate variations for at least the past 1.5 Ma despite changing glacial boundary conditions. A strong correlation exists between millennial increases in planktic δ18O (cooling) and decreases in benthic δ13C, indicating that millennial variations in North Atlantic surface temperature are mirrored by changes in deep-water circulation and remineralization of carbon in the abyssal ocean. We find strong evidence that climate variability on millennial and orbital scales is coupled across different timescales and interacts in both directions, which may be important for linking internal climate dynamics and external astronomical forcing.
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- 2023
3. Abrupt intrinsic and extrinsic responses of southwestern Iberian vegetation to millennial‐scale variability over the past 28 ka
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David A. Hodell, Mark A. Maslin, Blanca Ausín, Timothy I. Eglinton, Francesco Muschitiello, Negar Haghipour, Laurie Menviel, Polychronis C Tzedakis, Vasiliki Margari, Belen Martrat, Anna Cutmore, Cutmore, A [0000-0003-2560-5076], Apollo - University of Cambridge Repository, and Ministerio de Ciencia e Innovación (España)
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010506 paleontology ,Holocene ,010504 meteorology & atmospheric sciences ,Scale (ratio) ,abrupt climate change ,Marine Isotope Stage 2 ,pollen ,southwest Iberia ,Paleontology ,15. Life on land ,01 natural sciences ,Arts and Humanities (miscellaneous) ,13. Climate action ,Earth and Planetary Sciences (miscellaneous) ,medicine ,Abrupt climate change ,Research article ,Physical geography ,medicine.symptom ,Vegetation (pathology) ,Geology ,0105 earth and related environmental sciences - Abstract
We present new high-resolution pollen records combined with palaeoceanographic proxies from the same samples in deep-sea cores SHAK06-5K and MD01-2444 on the southwestern Iberian Margin, documenting regional vegetation responses to orbital and millennial-scale climate changes over the last 28 ka. The chronology of these records is based on high-resolution radiocarbon dates of monospecific samples of the planktonic foraminifera Globigerina bulloides, measured from SHAK06-5K and MD01-2444 and aligned using an automated stratigraphical alignment method. Changes in temperate and steppe vegetation during Marine Isotope Stage 2 are closely coupled with sea surface temperature (SST) and global ice-volume changes. The peak expansion of thermophilous woodland between similar to 10.1 and 8.4 cal ka BP lags behind the boreal summer insolation maximum by similar to 2 ka, possibly arising from residual high-latitude ice-sheets into the Holocene. Rapid changes in pollen percentages are coeval with abrupt transitions in SSTs, precipitation and winter temperature at the onset and end of Heinrich Stadial 2, the ice-rafted debris event and end of Heinrich Stadial 1, and the onset of the Younger Dryas, suggesting extrinsically forced southwestern Iberian ecosystem changes by abrupt North Atlantic climate events. In contrast, the abrupt decline in thermophilous elements at similar to 7.8 cal ka BP indicates an intrinsically mediated abrupt vegetation response to the gradually declining boreal insolation, potentially resulting from the crossing of a seasonality of precipitation threshold. (C) 2021 The Authors. Journal of Quaternary Science Published by John Wiley & Sons, Ltd., Journal of Quaternary Science, 37 (3), ISSN:0267-8179, ISSN:1099-1417
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- 2021
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4. Persistent millennial-scale climate variability in Southern Europe during Marine Isotope Stage 6
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M. R. Frogley, Vasiliki Margari, Graham P. Wilson, Katherine H Roucoux, Polychronis C Tzedakis, Melanie J. Leng, Philip D. Hughes, Tim Jones, University of St Andrews. School of Biology, University of St Andrews. School of Geography & Sustainable Development, and University of St Andrews. Environmental Change Research Group
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Pharmacology ,Marine isotope stage ,GB ,Southern Europe ,biology ,Marine Isotope Stage 6 ,NDAS ,Millennial-scale climate variability ,Structural basin ,biology.organism_classification ,Isotopes of oxygen ,Oceanography ,Diatom ,Archaeology ,Stage (stratigraphy) ,GB Physical geography ,SDG 13 - Climate Action ,Geography. Anthropology. Recreation ,East Asian Monsoon ,Stadial ,SDG 14 - Life Below Water ,Geology ,CC1-960 ,Teleconnection - Abstract
GW gratefully acknowledges the financial support provided by The University of Chester. Exploring the mode and tempo of millennial-scale climate variability under evolving boundary conditions can provide insights into tipping points in different parts of the Earth system, and can facilitate a more detailed understanding of climate teleconnections and phase relationships between different Earth system components. Here we use fossil diatom and stable carbon and oxygen isotope analysis of lake sediment deposits (core I-284) from the Ioannina basin, NW Greece, to explore in further detail millennial-scale climate instability in southern Europe during Marine Isotope Stage 6 (MIS 6; ca. 185‒130 ka). This interval correlates with the Vlasian Stage in Greece and the Late Saalian Substage in northern Europe, which were both characterised by extensive glaciations. The new dataset resolves at least 18 discrete warmer/wetter intervals, many of which were associated with strong Asian Monsoon events and North Atlantic interstadials. A number of cooler/drier intervals are also identified in the I-284 record, which are typically associated with weaker Asian Monsoon events and North Atlantic stadials, consistent with a variable Atlantic Meridional Overturning Circulation. Unlike the subdued changes in tree populations that are observed at Ioannina during mid-to-late MIS 6, the diatom record contains frequent high-amplitude oscillations in species assemblages, pointing to its sensitivity at a time when the lake system must have been close to environmental thresholds. Millennial-scale variability in diatom species assemblages continues into late MIS 6 at Ioannina, contributing important evidence for an emerging picture of frequent and persistent climate instability even at times of high global ice volume. Publisher PDF
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- 2021
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5. Fast and slow components of millennial-scale climate changes
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Maryline J Vautravers, Mohamed Ezat, Chronis Tzedakis, David A. Hodell, Rachael H. Rhodes, Emilie Capron, Vasiliki Margari, Joan O. Grimalt, Laurie Menviel, Belen Martrat, and Luke C Skinner
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Scale (ratio) ,Climatology ,Environmental science ,Climate change - Abstract
Despite a substantial body of evidence on millennial-scale climate variability during Marine Isotope Stage 3, uncertainty remains over the precise sequence of changes in different parts of the climate system, and ultimately their causes. Here, we present results of joint marine and terrestrial proxy analyses from the Portuguese Margin, showing the typical succession of cold stadials and warm interstadials over the interval 35-57 ka, with most extreme changes occurring during Heinrich Stadials (HS). The planktonic and benthic foraminiferal isotope records map onto Greenland and Antarctic temperature variations, respectively, while the pollen record bears a close similarity to changes in the Asian summer monsoon, atmospheric methane and dust concentrations, indicating coupled changes in hydroclimate in middle-to-low latitudes. Closer inspection of HS4 and HS5 reveals considerable structure, with a relatively fast transition to maximum cooling and aridity associated with a peak in ice-rafted detritus, containing detrital carbonate grains originating from the Hudson Strait. This was followed by an interval of slowly increasing sea-surface temperatures (SST) and moisture availability, in line with evidence indicating a gradual evolution in low-latitude hydroclimate. A climate model experiment closely reproduces the gradual increase in SST and precipitation in W. Iberia during the final part of HS4 as a result of the recovery of the Atlantic overturning circulation, but does not capturethe abrupt warming in Greenland. What emerges is a diversity of response timescales, from centuries in low-to-mid latitude SST and precipitation to decades in Greenland temperatures.
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- 2020
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6. On the use of Artificial Neural Networks for the calm water resistance prediction of MARAD Systematic Series’ hullforms
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Aphrodite Kanellopoulou, George Zaraphonitis, and Vasiliki Margari
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Environmental Engineering ,Water resistance ,Artificial neural network ,Series (mathematics) ,Computer science ,020209 energy ,020101 civil engineering ,Ocean Engineering ,02 engineering and technology ,Residual ,0201 civil engineering ,Hull ,0202 electrical engineering, electronic engineering, information engineering ,Resistance coefficient ,Marine engineering - Abstract
The present study investigates the use of Artificial Neural Networks (ANNs) for the resistance prediction of hullforms designed according to the MARAD Systematic Series. This series comprises 16 full hullforms, specifically designed for use as bulk carriers and tankers. Experimental data for the residual resistance coefficient of these hulls provided by MARAD in a series of diagrams have been used to train and evaluate a series of neural networks aiming to estimate the residual resistance coefficient of ships designed according to the MARAD Series. The adopted procedure along with the obtained results are presented and discussed.
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- 2018
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7. Towards a Middle Pleistocene terrestrial climate reconstruction based on herpetofaunal assemblages from the Iberian Peninsula: State of the art and perspectives
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Katherine H Roucoux, José Alberto Cruz Silva, Hugues-Alexandre Blain, Vasiliki Margari, and Juan Manuel Jiménez Arenas
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010506 paleontology ,Archeology ,Global and Planetary Change ,geography ,Climate pattern ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Pleistocene ,Range (biology) ,Geology ,Context (language use) ,01 natural sciences ,Peninsula ,Interglacial ,Physical geography ,Precipitation ,Glacial period ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences - Abstract
The pattern of the varying climatic conditions in southern Europe over the last million years is well known from isotope studies on deep-ocean sediment cores and the long pollen records that have been produced for lacustrine and marine sedimentary sequences from Greece, Italy and the Iberian margin. However, although relative glacial and interglacial intensities are well studied, there are still few proxies that permit quantitative terrestrial temperature and precipitation reconstruction. In this context, fauna-based climate reconstructions based on evidence preserved in archaeological or palaeontological sites are of great interest, even if they only document short windows of that climate variability, because (a) they provide a range of temperature and precipitation estimates that are understandable in comparison with present climate; (b) they may allow the testing of predicted temperature changes under scenarios of future climate change; and (c) quantitative temperature and precipitation estimates for past glacials and interglacials for specific regions/latitudes can help to understand their effects on flora, fauna and hominids, as they are directly associated with those cultural and/or biological events. Moreover such reconstructions can bring further arguments to the discussion about important climatic events like the Mid-Bruhnes Event, a climatic transition between moderate warmths and greater warmths during interglacials. In this paper we review a decade of amphibian- and reptile-based climate reconstructions carried out for the Iberian Peninsula using the Mutual Ecogeographic Range method in order to present a regional synthesis from MIS 22 to MIS 6, discuss the climate pattern in relation to the Mid-Bruhnes Event and the thermal amplitude suggested by these estimates and finally to identify the chronological gaps that have still to be investigated.
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- 2018
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8. The MIS 13 interglacial at Ceprano, Italy, in the context of Middle Pleistocene vegetation changes in southern Europe
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Giorgio Manzi, Donatella Magri, Polychronis C Tzedakis, Vasiliki Margari, Katherine H Roucoux, and University of St Andrews. School of Geography & Sustainable Development
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Marine isotope stage ,010506 paleontology ,Archeology ,Middle Pleistocene ,Southern Europe ,010504 meteorology & atmospheric sciences ,Environmental change ,Context (archaeology) ,Pleistocene ,NDAS ,Climate change ,01 natural sciences ,MIS 13 ,SDG 14 - Life Below Water ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,SDG 15 - Life on Land ,Global and Planetary Change ,Vegetation ,GE ,Geology ,Geography ,Archaeology ,Interglacial ,Period (geology) ,Pollen ,Ceprano ,Physical geography ,archaeology ,ceprano ,middle pleistocene ,pollen ,southern europe ,vegetation ,global and planetary change ,ecology evolution ,behavior and systematics ,archeology arts and humanities ,archeology ,geology ,GE Environmental Sciences - Abstract
PCT and VM gratefully acknowledge support from The Leverhulme Trust through a research project grant (F/00 122/AH) towards the palynological investigation of the Ceprano cores. Excavations 2001–2006 at Campogrande were directed by Itallo Biddittu and GM, authorized by the Soprintendenza Archeologica del Lazio and co-financed by research grants from the SAPIENZA, University of Rome. Drillings at Campogrande were jointly financed and supervised by the Istituto per la Dinamica dei Processi Ambientali (CNR, Venice) and by the Istituto Italiano di Paleontologia Umana (Rome). Climatic and environmental changes of the Middle Pleistocene in Europe provide the context for an important phase in the evolution and dispersal of early hominins. Pollen records from terrestrial and marine sediment sequences reveal patterns not usually visible in palaeoenvironmental reconstructions from archaeological sites alone and show that hominin evolution took place against a background of marked environmental change as forests expanded and contracted in concert with global and regional climatic shifts. It is rare to find archaeological material in stratigraphically long and continuous palaeoenvironmental sequences, yet this is what is needed to enable particular phases of hominin evolution to be securely associated with climatic and environmental changes. At the well-known Middle Pleistocene archaeological site of Ceprano in Italy we have been able to produce a pollen record from the sedimentary unit directly below the stratum of the hominin remains. The new pollen data from Ceprano are presented here in full for the first time and provide a detailed picture of interglacial vegetation development during Marine Isotope Stage (MIS) 13. This evidence contributes significantly to our knowledge of the spatial heterogeneity of ecosystem responses to climatic change during this period and helps to further constrain the age of the hominin remains. New sites combining both archaeology and long, continuous high quality palaeoecological records would help clarify the relationship between hominin presence and palaeoclimatic and palaeoenvironmental conditions. In the meantime, better communication between the research communities can also go a long way to improving our understanding of the links between the two. Postprint
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- 2018
9. Biogenic magnetite, detrital hematite, and relative paleointensity in Quaternary sediments from the Southwest Iberian Margin
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Vasiliki Margari, David A. Hodell, Luke C Skinner, Polychronis C Tzedakis, Michael S. Kesler, and James E.T. Channell
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Polar front ,Magnetotactic bacteria ,Geochemistry ,Hematite ,chemistry.chemical_compound ,Geophysics ,chemistry ,Space and Planetary Science ,Geochemistry and Petrology ,visual_art ,Earth and Planetary Sciences (miscellaneous) ,visual_art.visual_art_medium ,Stadial ,Glacial period ,Sulfate ,Sea level ,Geology ,Magnetite - Abstract
Magnetic properties of late Quaternary sediments on the SW Iberian Margin are dominated by bacterial magnetite, observed by transmission electron microscopy (TEM), with contributions from detrital titanomagnetite and hematite. Reactive hematite, together with low organic matter concentrations and the lack of sulfate reduction, lead to dissimilatory iron reduction and availability of Fe(II) for abundant magnetotactic bacteria. Magnetite grain-size proxies ( κ ARM / κ and ARM/IRM) and S-ratios (sensitive to hematite) vary on stadial/interstadial timescales, contain orbital power, and mimic planktic δ 18 O . The detrital/biogenic magnetite ratio and hematite concentration are greater during stadials and glacial isotopic stages, reflecting increased detrital (magnetite) input during times of lowered sea level, coinciding with atmospheric conditions favoring hematitic dust supply. Magnetic susceptibility, on the other hand, has a very different response being sensitive to coarse detrital multidomain (MD) magnetite associated with ice-rafted debris (IRD). High susceptibility and/or magnetic grain-size coarsening, mark Heinrich stadials (HS), particularly HS2, HS3, HS4, HS5, HS6 and HS7, as well as older Heinrich-like detrital layers, indicating the sensitivity of this region to fluctuations in the position of the polar front. Relative paleointensity (RPI) records have well-constrained age models based on planktic δ 18 O correlation to ice-core chronologies, however, they differ from reference records (e.g. PISO) particularly in the vicinity of glacial maxima, mainly due to inefficient normalization of RPI records in intervals of enhanced hematite input.
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- 2013
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10. Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka
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George D. Kamenov, David A. Hodell, Guy Rothwell, Luke C Skinner, Suzanne Maclachlan, Vasiliki Margari, James E.T. Channell, Simon J Crowhurst, and Polychronis C Tzedakis
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geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Orbital forcing ,Paleontology ,Speleothem ,Sediment ,010502 geochemistry & geophysics ,Oceanography ,01 natural sciences ,Ice core ,13. Climate action ,Paleoceanography ,Climatology ,100,000-year problem ,Upwelling ,Maxima ,Geology ,0105 earth and related environmental sciences - Abstract
Here we report 420?kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment “redness” (a* and 570–560?nm) and the ratio of long-chain alcohols to n-alkanes (C26OH/(C26OH?+?C29)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7–8?ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420?ka) for detecting 100?kyr eccentricity cycles, the phase relationships support those obtained by Shackleton []. Antarctic temperature and the Iberian Margin alcohol ratios (C26OH/(C26OH?+?C29)) lead eccentricity maxima by 6?kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO2, CH4, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific ?18Oseawater) lags eccentricity maxima by 10?kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100?kyr cycle.
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- 2013
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11. Supplementary material to 'The ACER pollen and charcoal database: a global resource to document vegetation and fire response to abrupt climate changes during the last glacial period'
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Maria Fernanda Sánchez Goñi, Stéphanie Desprat, Anne-Laure Daniau, Franck C. Bassinot, Josué M. Polanco-Martínez, Sandy P. Harrison, Judy R. M. Allen, R. Scott Anderson, Hermann Behling, Raymonde Bonnefille, Francesc Burjachs, José S. Carrión, Rachid Cheddadi, James S. Clark, Nathalie Combourieu-Nebout, Colin J. Courtney-Mustaphi, George H. Debusk, Lydie M. Dupont, Jemma M. Finch, William J. Fletcher, Marco Giardini, Catalina González, William D. Gosling, Laurie D. Grigg, Eric C. Grimm, Ryoma Hayashi, Karin Helmens, Linda E. Heusser, Trevor Hill, Geoffrey Hope, Brian Huntley, Yaeko Igarashi, Tomohisa Irino, Bonnie Jacobs, Gonzalo Jiménez-Moreno, Sayuri Kawai, Peter Kershaw, Fujio Kumon, Ian T. Lawson, Marie-Pierre Ledru, Anne-Marie Lézine, Ping Mei Liew, Donatella Magri, Robert Marchant, Vasiliki Margari, Francis E. Mayle, Merna McKenzie, Patrick Moss, Stefanie Müller, Ulrich C. Müller, Filipa Naughton, Rewi M. Newnham, Tadamichi Oba, Ramón Pérez-Obiol, Roberta Pini, Cesare Ravazzi, Katy H. Roucoux, Stephen M. Rucina, Louis Scott, Hikaru Takahara, Polichronis C. Tzedakis, Dunia H. Urrego, Bas van Geel, B. Guido Valencia, Marcus J. Vandergoes, Annie Vincens, Cathy L. Whitlock, Debra A. Willard, and Masanobu Yamamoto
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- 2017
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12. Reply: Correlation of a widespread Pleistocene tephra marker from the Nisyros-Yali volcanic complex, Greece
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David M. Pyle and Vasiliki Margari
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Mediterranean climate ,geography ,Geophysics ,geography.geographical_feature_category ,Stratigraphy ,Volcano ,Pleistocene ,Geochemistry and Petrology ,Pumice ,Geochemistry ,Tephra ,Geomorphology ,Geology - Published
- 2016
13. Vegetation history of the penultimate glacial period (Marine isotope stage 6) at Ioannina, north-west Greece
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Vasiliki Margari, Polychronis C Tzedakis, Katherine H Roucoux, and Ian T. Lawson
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Marine isotope stage ,education.field_of_study ,Population ,Paleontology ,Vegetation ,Oceanography ,Arts and Humanities (miscellaneous) ,Ice core ,Earth and Planetary Sciences (miscellaneous) ,Period (geology) ,Glacial period ,education ,Geology ,Sea level ,Chronology - Abstract
The vegetational history of the penultimate glacial period, Marine Isotope Stage (MIS) 6 (c. 185-135 ka), has remained relatively unexplored. Here we present a new record from the Ioannina basin, north-west Greece, which constitutes the highest-resolution terrestrial pollen record for this interval produced to date. It shows that the vegetation history of MIS 6 in this region can be divided into two parts: an early period (185-155 ka) with pronounced oscillations in tree population extent, and a later period (155 135 ka) with much smaller tree populations and subdued oscillations. This pattern is analogous to the MIS 3/MIS 2 division during the last glacial in the same sequence, although the early part of MIS 6 had larger Pinus populations and fewer temperate trees relative to the equivalent interval in MIS 3. This implies cooler and wetter conditions, which is somewhat counterintuitive given the high summer insolation during MIS 6e, but is in line with other palaeoclimatic evidence from the Mediterranean. Comparison with North Atlantic records suggests that despite the absence of pronounced iceberg discharges during MIS 6, North Atlantic millennial-scale variability had a significant downstream impact on tree populations in north-west Greece. Copyright (C) 2011 John Wiley & Sons, Ltd.
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- 2011
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14. The nature of millennial-scale climate variability during the past two glacial periods
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Luke C Skinner, Vasiliki Margari, Andrey Ganopolski, Polychronis C Tzedakis, N.J. Shackleton, and Maryline J Vautravers
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Oceanography ,Shutdown of thermohaline circulation ,Climatology ,Interglacial ,Northern Hemisphere ,General Earth and Planetary Sciences ,Climate change ,Thermohaline circulation ,Glacial period ,Water cycle ,Geology ,Iceberg - Abstract
Periodic iceberg discharges during the last glacial period led to a slowdown of the Atlantic meridional overturning circulation. Sediment records from the Portuguese margin show that similar events punctuated the penultimate glacial period as well, although their duration and broader climatic impacts were modified by different background climate conditions. During the last glacial period, iceberg discharges into the North Atlantic disrupted the meridional overturning circulation, leading to cooling in the Northern Hemisphere and warming in Antarctica1,2. This asymmetric response can be explained by a bipolar see-saw mechanism3,4,5, whereby changes in the strength of the meridional overturning circulation lead to changes in the interhemispheric heat transport. It is unclear, however, to what extent the response of the overturning circulation is a function of freshwater flux and boundary climate conditions4. Here we use foraminiferal isotope and pollen records from the Portuguese margin to reconstruct surface- and deep-water hydrography and atmospheric changes during the last and penultimate glacial periods. When we compare our records with temperature reconstructions from Antarctica6, we find that the bipolar see-saw was a characteristic feature of both glacial periods. However, the comparison also underlines the dependence of the bipolar see-saw on background climate and magnitude of iceberg discharge. It also suggests that an intensified hydrological cycle may lead to a weaker overturning circulation with a smaller disruption threshold and extended North Atlantic stadial durations.
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- 2010
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15. Character of vegetational and environmental changes in southern Europe during the last glacial period; evidence from Lesvos Island, Greece
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Philip L. Gibbard, Polychronis C Tzedakis, Vasiliki Margari, and Charlotte Bryant
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Palynology ,Marine isotope stage ,Archeology ,Global and Planetary Change ,geography ,geography.geographical_feature_category ,Steppe ,Geology ,Vegetation ,Arid ,law.invention ,Oceanography ,law ,Glacial period ,Radiocarbon dating ,Stadial ,Ecology, Evolution, Behavior and Systematics - Abstract
This paper presents high-resolution results of palynological and sedimentological analyses undertaken on two sediment cores from the Megali Limni (ML) basin, an area characterised by serpentine soils, in the southeastern part of Lesvos Island, Greece. Six tephra horizons and multiple radiocarbon dates provide independent controls towards the development of a chronological framework. The composite pollen record spans the period from 22 to 62 thousand years ago (ka) BP and shows a number of oscillations between steppe, forest-steppe and forest, in concert with North Atlantic millennial-scale variability. Vegetation during the late Marine Isotope Stage (MIS) 4 was grassland/steppe, indicating cold and arid conditions, while sediment composition suggests increased erosion rates. Arboreal populations (dominated by Pinus and to a lesser extent deciduous Quercus) expanded during MIS 3 interstadials, suggesting increases in precipitation and temperature. Within the course of the longer interstadials, changes in vegetation composition point to a trend towards increased aridity and sometimes decreasing winter temperatures. During intervening stadials, vegetation was composed mainly of Artemisia, Chenopodiaceae and Gramineae, indicating reversals to arid and cold conditions, with most extreme conditions recorded during stadials corresponding to Heinrich Events. During the course of MIS 3, the basin was progressively infilled with sediments. Only a small portion of MIS 2 is represented in the sequence, showing a short-lived expansion of arboreal populations. Comparisons with other pollen sequences from southern Europe underscore the important role of Pinus throughout the last glacial period, a reflection of the serpentine soils of the Megali Limni area, where Pinus brutia dominates today.
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- 2009
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16. Interglacials of the last 800,000years
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Zohra Mokeddem, Valérie Masson-Delmotte, Ayako Abe-Ouchi, Eric W. Wolff, Kenji Kawamura, Michel Crucifix, Qiuzhen Yin, Isabel Cacho, A. Ganopolski, Vasiliki Margari, Patrizia Ferretti, Dominique Raynaud, Belen Martrat, Harunur Rashid, Michael Schulz, Luke C Skinner, Amaelle Landais, Joan O. Grimalt, André Berger, Victor Brovkin, Emilie Capron, Frédéric Parrenin, Carlo Barbante, Bette L. Otto-Bliesner, N. Vazquez Riveiros, A.A. Prokopenko, K. Pol, Jerry F. McManus, C. Mangili, Polychronis C Tzedakis, David A. Hodell, Bärbel Hönisch, Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Glaces et Continents, Climats et Isotopes Stables (GLACCIOS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), UCL - SST/ELI/ELIC - Earth & Climate, Hodell, David [0000-0001-8537-1588], Skinner, Luke [0000-0002-5050-0244], Wolff, Eric [0000-0002-5914-8531], Apollo - University of Cambridge Repository, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Université Catholique de Louvain (UCL), and Past Interglacials Working Group of PAGES
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010506 paleontology ,010504 meteorology & atmospheric sciences ,sub-01 ,review ,Settore GEO/12 - Oceanografia e Fisica dell'Atmosfera ,Climate change ,Review ,01 natural sciences ,interglacials ,Quaternary ,Interglacials ,Períodes glacials ,Settore GEO/01 - Paleontologia e Paleoecologia ,Deglaciation ,Paleoclimatologia ,Settore CHIM/01 - Chimica Analitica ,Glacial period ,Paleoclimatology ,Holocene ,Sea level ,0105 earth and related environmental sciences ,Interglacials, Review, Quaternary ,Milankovitch cycles ,quaternary ,Northern Hemisphere ,Settore GEO/02 - Geologia Stratigrafica e Sedimentologica ,Geophysics ,13. Climate action ,[SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology ,Glacial epoch ,Settore GEO/08 - Geochimica e Vulcanologia ,Climatology ,Interglacial ,Geology - Abstract
Interglacials, including the present (Holocene) period, are warm, low land ice extent (high sea level), end-members of glacial cycles. Based on a sea level definition, we identify eleven interglacials in the last 800,000 years, a result that is robust to alternative definitions. Data compilations suggest that despite spatial heterogeneity, Marine Isotope Stages (MIS) 5e (last interglacial) and 11c (∼400 ka ago) were globally strong (warm), while MIS 13a (∼500 ka ago) was cool at many locations. A step change in strength of interglacials at 450 ka is apparent only in atmospheric CO2 and in Antarctic and deep ocean temperature. The onset of an interglacial (glacial termination) seems to require a reducing precession parameter (increasing Northern Hemisphere summer insolation), but this condition alone is insufficient. Terminations involve rapid, nonlinear, reactions of ice volume, CO2, and temperature to external astronomical forcing. The precise timing of events may be modulated by millennial-scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere. A variety of temporal trends is observed, such that maxima in the main records are observed either early or late in different interglacials. The end of an interglacial (glacial inception) is a slower process involving a global sequence of changes. Interglacials have been typically 10-30 ka long. The combination of minimal reduction in northern summer insolation over the next few orbital cycles, owing to low eccentricity, and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future. ©2015. The Authors., This paper arose as a result of a succession of workshops of the Past Interglacials Group (PIGS), sponsored by the Past Global Changes Project (PAGES). The authors acknowledge the contributions of all participants at those workshops, of whom the listed authors are only a subset. Numerous funding agencies have contributed to the work of this paper including NSF (USA), NERC and The Royal Society (UK), F.R.S-FNRS (Belgium), and SNF (Switzerland).
- Published
- 2016
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17. Mediterranean tephra stratigraphy revisited: Results from a long terrestrial sequence on Lesvos Island, Greece
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Vasiliki Margari, David M. Pyle, Charlotte Bryant, and Philip L. Gibbard
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Hellenic arc ,geography ,geography.geographical_feature_category ,Pleistocene ,Pyroclastic rock ,law.invention ,Volcanic rock ,Paleontology ,Geophysics ,Dense-rock equivalent ,Geochemistry and Petrology ,law ,Radiocarbon dating ,Glacial period ,Tephra ,Geology - Abstract
A composite 40.2 m sediment sequence from Megali Limni, Lesvos Island, Greece, spanning the interval from 22 to 62 ka BP, contains six Pleistocene tephra layers, which can be identified on the basis of their major and trace elemental compositions. The youngest tephra deposit correlates with the 22 ka Y-2 marker, erupted during the Cape Riva eruption of Santorini. The second tephra originates from the Campanian area in Italy and corresponds to the Campanian Ignimbrite eruption (the 39 ka Y-5 marker). The next two layers are compositionally identical, and originate from Eastern islands of the Hellenic Arc; they could potentially correspond to the Upper and Lower Pumice eruptions of Nisyros or some other previously unidentified eruption from Yali. The fifth stratum corresponds to the Y-6 marker, which erupted during the Green Tuff eruption of the Pantelleria Island. The source of the last tephra layer is either the Yali-Nisyros complex or Central Anatolia; no specific corresponding eruption has yet been found. Long distal tephra sequences within terrestrial settings are rare in the eastern Mediterranean and the Megali Limni record contains the most complete sequence to date. Moreover, its age model, based on independent chronologies such as AMS and conventional radiocarbon dates and high-resolution pollen stratigraphy, provides new ages for these eruptions and places them within the context of the millennial-scale palaeoenvironmental variability of the last glacial period. Finally, the recognition of the Pantelleria tephra in this locality considerably extends the confirmed Northerly and Easterly distribution of this widespread and distinctive unit, while the existence of the Nisyros-Yali tephras on Lesvos refutes the current belief of limited tephra dispersal and small magnitude of these eruptions. © 2007 Elsevier B.V. All rights reserved.
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- 2007
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18. Case study of transfusion related acute lung injury in intensive care unit
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Vasiliki Margari and Panagiota Bompou–Magoula
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medicine.medical_specialty ,ARDS ,business.industry ,Common method ,medicine.disease ,Intensive care unit ,law.invention ,law ,Diabetes mellitus ,Acute care ,medicine ,Platelet ,Intensive care medicine ,business ,Diabetic coma ,Transfusion-related acute lung injury - Abstract
Transfusion is a common method of treatment of haemorrhagic events of patients treated in the Intensive Care Unit (ICU). Nonetheless, it involves various dangers, in many cases fatal, such as transfusion related acute lung injury (TRALI). This article refers to the case encountered during our traineeship in the ICU. It is about a 47-year-old man, who was transported to us from another tertiary acute care facility intubated due to diabetic coma. After 39 days of treatment in the ICU, the acute diabetes mellitus, the hemodynamic instability and the electrolyte disorders were regulated. However, he started to have diffuse haemorrhagic events due to intestinal necrosis and required transfusion of blood factors. After the transfusion of Platelets (PLT) he developed Acute Respiratory Distress Syndrome (ARDS), which evolved to TRALI and finally the death of the patient occurred.
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- 2015
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19. Multi-decadal temperature changes off Iberia over the last two deglaciations and interglacials and their connection with the polar climate
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Luke C Skinner, David A Hodell, Vasiliki Margari, Belen Martrat, Polychronis C Tzedakis, and Joan O. Grimalt
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Temperature changes ,Climatology ,Interglacial ,Atmospheric sciences ,Polar climate ,Geology ,Connection (mathematics) - Abstract
The Iberian margin provides climatic and environmental sediment records with multi-decadal resolution over the last two deglaciations and interglacials. These records allow us to identify climatic structures and discuss interhemispherical connections.
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- 2015
20. Millennial-scale variability during the last glacial in vegetation records from Europe
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Filipa Naughton, Polychronis C Tzedakis, Brian Huntley, William J. Fletcher, Laurent Londeix, Katy Roucoux, Ulrich C Müller, Rachid Cheddadi, Maria Fernanda Sanchez Goñi, Judy R M Allen, Nathalie Combourieu-Nebout, Donatella Magri, Vasiliki Margari, Elena Novenko, Ian T. Lawson, Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Paléocéanographie (PALEOCEAN), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), and Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
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[SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere ,010506 paleontology ,Archeology ,Global and Planetary Change ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Taiga ,Temperate forest ,Geology ,Vegetation ,15. Life on land ,01 natural sciences ,Tundra ,Grassland ,Geography ,Oceanography ,Ice core ,Continental margin ,13. Climate action ,Glacial period ,[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment ,Ecology, Evolution, Behavior and Systematics ,ComputingMilieux_MISCELLANEOUS ,0105 earth and related environmental sciences - Abstract
This paper evaluates the evidence for millennial-scale variability in pollen records of the last glacial (Marine Isotope Stages 4, 3, and 2; 73.5–14.7 calendar ka BP) from the European continent, taking into account information derived from long, continuous terrestrial records, the fragmentary northern European terrestrial record, and marine pollen records of the European continental margins. Pollen records from these numerous European sites provide evidence for multiple intervals of relatively warm and humid conditions during the last glacial, which promoted the establishment of grassland and shrub tundra in northwestern Europe, shrub- and forest-tundra in northeastern Europe, open boreal forest in central western Europe and the Alpine region, and open temperate forest in southern Europe. The northern limit for temperate forest development during these intervals was at ∼45°N, with a subsequent northward transition to tundra across a latitudinal band of ∼15° in western and central Europe, and a greater northward extension of boreal forest in eastern Europe, with boreal forest elements detected close to their present-day limits at ∼70°N. A much smaller number of sites with sufficiently high temporal resolution provide evidence that warming intervals correspond to millennial-scale variability as recorded in Greenland ice cores. A synthesis of sites providing high-resolution terrestrial and marine records from Europe is undertaken in order to examine geographical and temporal patterns in the expression of Dansgaard–Oeschger (D–O) cycles in the European vegetation. Detailed comparison of temperate forest development at these sites during four specific D–O cycles (D–O 16–17, 14, 12 and 8) reveals contrasts between vegetation response at southernmost European latitudes (below 40°N) and at latitudes above 40°N. At southernmost latitudes, marked forest development occurred during all four D–O cycles including D–O 16–17 and 8, while at latitudes above 40°N, forest development was stronger during D–O 14 and 12 than either D–O 16–17 or 8.
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- 2010
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21. The new chronology of the Ceprano calvarium (Italy)
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Rita Teresa Melis, Maurizio Barbieri, Polychronis C Tzedakis, Maria Rita Palombo, Italo Biddittu, Mario Barbieri, Giorgio Manzi, Salvatore Milli, Donatella Magri, Barbara Saracino, Massimo Ruffo, Vincenzo Celiberti, Annalisa Zarattini, Mauro Rubini, and Vasiliki Margari
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Palynology ,paleolithic modes 1/2 ,Early Pleistocene ,biology ,Pleistocene ," archaic" homo ,geochronology ,taphonomy ,"archaic" homo ,biology.organism_classification ,Paleontology ,Anthropology ,middle pleistocene ,palynology ,Homo erectus ,Hammerstone ,Ecology, Evolution, Behavior and Systematics ,Geology ,Acheulean ,Oldowan ,Chronology - Abstract
IntroductionThe fossil human calvarium known as Ceprano (Latium, Italy) iscommonly dated to 800e900 ka, on the basis of geological andstratigraphical inferences (Ascenzi et al., 1996, 2000). This chro-nology appeared somehow consistent with the “archaic”morphology of the calvarium and its peculiar combination offeatures, which gave rise to a controversial taxonomic identity(Ascenzietal.,1996,2000;Clarke,2000;Manzietal.,2001;Mallegniet al., 2003; Bruner and Manzi, 2005, 2007). A re-evaluation of thislate Early Pleistocene chronology has been advanced by Muttoniet al. (2009) on the basis of paleomagnetic data. This hypothesis istested here, based on the combined evaluation of the multidisci-plinary evidence collected during recent systematic excavations.The specimen was discovered on 13 March 1994 within a claylevel partly destroyed by bulldozers working for a new road ina locality known as Campogrande (Fig. 1), about 3 km SW ofCeprano and 100 km SE of Rome, in Central Italy (for review andreferences see Manzi, 2004). The sediment containing the cranialfragments yielded more than 50 fragments. However, the craniumremainedincompletebecauseneitherportionsof thefacenorteethwere retrieved.The geological history of the Campogrande area was initiallyreferred to two main stratigraphic complexes (Ascenzi et al., 1996,2000; Ascenzi and Segre, 1997a,b): 1) upper fluvio-colluvialdeposits, with variable occurrence of volcanoclastic products (lateEarly to Middle Pleistocene); 2) lower lacustrine deposits, withoutvolcanoclastic products (roughly predating 1.0 Ma). The layercontaining the human calvarium was considered to belong to thelower portion of the upper stratigraphic complex. Its chronologywas inferred as more ancient than the Acheulean site of FontanaRanuccio, near Anagni (458 5.7 ka; Segre and Ascenzi, 1984),possiblyolderthan700ka,adatecorrespondingtothebeginningofthe volcanic activity in the region (Fornaseri, 1985).Given the presence in the Ceprano basin of various LowerPaleolithic assemblages, the archaic features of the calvarium andits hypothetical chronological position were considered in associ-ation with Mode 1, or Oldowan, techno-complexes (Biddittu,1984;Ascenzietal.,1996,2000).Mode1Paleolithicintheareacomefromvarious localities, including Arce, Castro de’ Volsci, Fontana Liri(Biddittu, 1972, 1974), as well as from the Campogrande area itself(see SOM-1), whose assemblages are characterized by flint orlimestone pebble-tools (mostly choppers, chopping-tools andpercussion tools), by debitage with hammerstone flakes, and byrelatively frequent cores, with a low degree of exploitation, mostoften unifacial, and high frequencyof cortical striking platforms. Asfor Mode 2 or Acheulean assemblages, new recent data (excava-tions 2001e2006; see below) have made it possible to bettercharacterize the material from Campogrande. These materials arenot numerically rich, but they yield evidence of each production
- Published
- 2010
22. Wide dispersal and deposition of distal tephra during the Pleistocene 'Campanian Ignimbrite/Y5' eruption, Italy
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Vasiliki Margari, Sergei N. Lisitsyn, Tjeerd H. van Andel, Graham D. Ricketts, David M. Pyle, Nicolai D. Praslov, and Andrei Sinitsyn
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Archeology ,Global and Planetary Change ,Explosive eruption ,Vulcanian eruption ,Pleistocene ,Earth science ,Geochemistry ,Geology ,Peléan eruption ,Dense-rock equivalent ,Magma ,Tephra ,Ecology, Evolution, Behavior and Systematics ,Volcanic ash - Abstract
A trachytic volcanic ash layer is widely distributed across south-western Russia, where it is found both in well-characterised archaeological contexts close to the Don River (the Paleolithic sites of Kostenki-Borschevo (51.4°N, 39.0°E), and in undisturbed geological contexts. This ash layer has all of the characteristics of a distal tephra fall deposit: it is fine grained and unimodal with a grain size of 60-170 μm, dominated by strongly elongate glass shard fragments. Chemical analysis confirms that this ash layer is a distal equivalent of the deposits of the ca 39.3 ka Campanian Ignimbrite eruption of the Phlegrean Fields, Italy, and correlates with the widely recognised Y5 ash layer in marine cores in the south-eastern Mediterranean. This work shows that ash particles can be dispersed over considerable distances (>2500 km) and areas (>1.5-3×106 km2) during large-magnitude explosive eruptions. The volume of the products associated with this event (31-50 km3 of magma erupted as fallout tephra, and a total volume of 105-210 km3 of magma, or 2.5-5×1014 kg) confirms the Campanian Ignimbrite/Y5 eruption as the most significant known volcanic eruption in Europe of the past 100 ka. This correlation places tight constraints on the absolute ages of a number of important archaeological horizons in southern Russia. © 2006 Elsevier Ltd. All rights reserved.
- Published
- 2006
23. The effect of immunotherapy on T-cell subsets in peripheral blood and bronchoalveolar lavage fluid in pollen-allergic patients
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A. Scheynius, Vasiliki Margari, G. Hallden, Sabina Rak, and S. Sörenson
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Adult ,Male ,Allergy ,Adolescent ,medicine.medical_treatment ,T cell ,T-Lymphocytes ,Immunology ,Peripheral blood mononuclear cell ,Flow cytometry ,Leukocyte Count ,T-Lymphocyte Subsets ,Forced Expiratory Volume ,Immunology and Allergy ,Medicine ,Humans ,Conjunctivitis, Allergic ,medicine.diagnostic_test ,business.industry ,Rhinitis, Allergic, Seasonal ,Immunotherapy ,HLA-DR Antigens ,Middle Aged ,medicine.disease ,Flow Cytometry ,Asthma ,Bronchoalveolar lavage ,medicine.anatomical_structure ,Desensitization, Immunologic ,Leukocytes, Mononuclear ,Pollen ,Female ,business ,Bronchoalveolar Lavage Fluid ,CD8 ,Blood sampling - Abstract
The effect of immunotherapy (IT) on T-cell subsets in peripheral blood and bronchoalveolar lavage fluid (BAL) was examined in 15 patients with rhinoconjunctivitis and asthma caused by sensitivity to birch pollen. They were treated with IT for 3 years. Seven patients were treated with highly standardized birch-pollen extract (Pharmacia, Sweden). Eight untreated patients served as controls. Histamine challenge, blood sampling, and BAL were performed before (January, February), and at the peak of, the birch-pollen season (May). The subpopulations of T cells in peripheral blood and BAL fluid were investigated by immunocytochemistry and flow cytometry. During the birch-pollen season, the percentage of CD3+ and CD4+ cells of blood mononuclear cells in the IT patients increased significantly (P < 0.03 and P < 0.02, respectively). The percentage of CD8+ cells remained unaltered. In control patients, no changes of T-cell subsets in the peripheral blood were observed. T-cell subsets in BAL did not change during the season in relation to preseasonal values for either IT-treated or non-IT-treated patients.
- Published
- 1993
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