1,721,253 research outputs found
Pollen profile IOAN249, Ioannina II, Greece
No full textThe EPD (http://www.europeanpollendatabase.net) accepted species name is given in the parameter comment. This dataset was archived on 2010-05-11 from the EPD database
An attempt at correlation between the Velay pollen sequence and the Middle Pleistocene stratigraphy from central Europe
No full textLong continuous lacustrine sequences constitute on the continent a precious toot for coupling the long term continental environmental changes with deep sea and ice core records, using the 'count from the top' method. Moreover, they can contribute to long distance correlation on the continent itself and thus help to classify discontinuous sedimentary records. Palynostratigraphical correlation is proposed here between the Velay long sequence and the late Middle Pleistocene series from Central Europe with special attention to temperate episodes. The similarities between the Praclaux and the Holsteinian Interglacial suggest that they are both contemporaneous with marine isotopic stage (MIS) 11. even if absolute dates are still divergent. The evidence of two major warm periods with an interglacial type of vegetation between the Holsteinian and the Eemian is confirmed by the Velay record. (C) 2001 Elsevier Science Ltd. All rights reserved
Lithology of sediment core IOAN249, Ioannina II, Greece
No full textThis dataset was archived on 2010-05-11 from the EPD database
Comment on "Glacial Survival of Boreal Trees in Northern Scandinavia"
No full textParducci et al. (Reports, 2 March 2012, p. 1083) fail to present convincing evidence for glacial survival of Pinus and Picea in northern Scandinavia. Their methodology does not exclude contamination. Additionally, they should consider the lack of suitable habitats, the apparent extinction of both taxa after deglacial warming, and alternative hypotheses for the distribution of the Picea genetic marker haplotype A
Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka
Get PDFHere 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 δ18Oseawater) 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
European vegetation during Marine Oxygen Isotope Stage-3
No full textEuropean vegetation during representative "warm" and "cold" intervals of stage-3 was inferred from pollen analytical data. The inferred vegetation differs in character and spatial pattern from that of both fully glacial and fully interglacial conditions and exhibits contrasts between warm and cold intervals, consistent with other evidence for stage-3 palaeoenvironmental fluctuations. European vegetation thus appears to have been an integral component of millennial environmental fluctuations during stage-3; vegetation responded to this scale of environmental change and through feedback mechanisms may have had effects upon the environment. The pollen-inferred vegetation was compared with vegetation simulated using the BIOME 3.5 vegetation model for climatic conditions simulated using a regional climate model (RegCM2) nested within a coupled global climate and vegetation model (GENESIS-BIOME). Despite some discrepancies in detail, both approaches capture the principal features of the present vegetation of Europe. The simulated vegetation for stage-3 differs markedly from that inferred from pollen analytical data, implying substantial discrepancy between the simulated climate and that actually prevailing. Sensitivity analyses indicate that the simulated climate is too warm and probably has too short a winter season. These discrepancies may reflect incorrect specification of sea surface temperature or sea-ice conditions and may be exacerbated by vegetation-climate feedback in the coupled global model. (C) 2003 Elsevier Science (USA). All rights reserved
The role of climate in the spread of modern humans into Europe
No full textThe spread of anatomically modern humans (AMH) into Europe occurred when shifts in the North Atlantic meridional overturning circulation triggered a series of large and abrupt climate changes during the last glacial. However, the role of climate forcing in this process has remained unclear. Here we present a last glacial record that provides insight into climate-related environmental shifts in the eastern Mediterranean region, i.e. the gateway for the colonisation of Europe by AMH. We show that the environmental impact of the Heinrich Event H5 climatic deterioration c. 48 kyr ago was as extreme as that of the glacial maximum of Marine Isotope Stage (MIS) 4 when most of Europe was deserted by Neanderthals. We argue that Heinrich H5 resulted in a similar demographic vacuum so that invasive AMH populations had the opportunity to spread into Europe and occupy large parts before the Neanderthals were able to reoccupy this territory. This spread followed the resumption of the Atlantic meridional overturning circulation at the beginning of Greenland Interstadial (GIS) 12 c. 47 kyr ago that triggered an extreme and rapid shift from desert-steppe to open woodland biomes in the gateway to Europe. We conclude that the extreme environmental impact of Heinrich H5 within a situation of competitive exclusion between two closely related hominids species shifted the balance in favour of modern human
Age model for Marine Isotope Stages (MIS) 34-35 and MIS 42-43 at IODP Site 339-U1385, southern Portuguese Margin
No full textBenthic and planktic oxygen and carbon isotopes, alkenone, pollen, and XRF data at IODP 339-U1385 for MIS 34-35 and MIS 42-43 southern Portuguese Margin
No full textWe report analyses of marine and terrestrial proxies from IODP Site 339-U1385 on the southern Portuguese Margin. We focus on two time-windows, representing distinct climatic contexts: one from the Early Pleistocene interval of 41-kyr glacial cycles (1335-1385 ka) and one from the Early–Middle Pleistocene Transition (~1110-1200 ka). Analyses were undertaken with respect to (i) oxygen isotopic composition of planktic and benthic foraminifera, reflecting changes in surface-water conditions, and global ice-volume and deep-water hydrography, respectively; (ii) the relative composition of C37 unsaturated alkenones, reflecting surface-water conditions; (iii) pollen content, providing an integrated picture of regional vegetation changes in southwestern Portugal; and (iv) X-ray fluorescence (XRF) sediment composition changes, reflecting variations in the relative proportion of detrital (Zr) and biogenic (Sr) sediment supply
(Table 1a) Age deterimantion of ODP Hole 165-1002D
No full textSediment depth is given in mbsf. All 14C errors are reported at 1 sigma. Reservoir age uncertainty is estimated to be ±100 years. The reported uncertainty (anal. uncert.) and reservoir age uncertainty (res. corr. uncert.) were added in quadrature to obtain a total 14C uncertainty for each date (total uncert.). The 1 sigma total 14C uncertainty has been added and subtracted from the reservoir-corrected 14C ages to provide 'Cariaco+' and 'Cariaco-', respectively. To match a sample 14C date, first add and subtract 1 sigma uncertainties (including reservoir age uncertainty, if applicable) from the sample 14C age, providing 'Sample+' and 'Sample-', respectively. The limits of the 14C age match are given by the shallowest depth at which 'Cariaco+' is greater than 'Sample-', and the deepest depth at which 'Sample+' is greater than 'Cariaco-'. The depths can then be translated to the sediment reflectance record for precise palaeoclimatic context
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