Kocsis L.,University of Lausanne |
Ozsvart P.,MTA MTM ELTE Research Group for Paleontology |
Becker D.,Jurassica Museum |
Ziegler R.,Staatliches Museum fur Naturkunde Stuttgart |
And 2 more authors.
Geology | Year: 2014
Terrestrial climatic data reflect variable and often conflicting responses to the global cooling event at the Eocene-Oligocene transition (ca. 34 Ma). Stable isotopic compositions of the tooth enamel of large, water-dependent, herbivorous terrestrial mammals are investigated here to better understand the European continental climate during the late Eocene- early Oligocene. High δ18OPO4 and δ13C values reflect a semiarid climate and ecosystem in the late Eocene. In the west-southwest region of Europe, these conditions prevailed until at least 33 Ma, after which it became more humid. A similar change was recorded north of the Alpine thrust, but it occurred 2 m.y. earlier. The north and west-southwest regions show a significant offset in δ18OPO4 composition between 35 and 31 Ma, indicating the influence of different air trajectories with different moisture sources (Atlantic versus Tethys). This also marks the presence of an orographic height in central Europe from the latest Eocene. After 31 Ma, a large drop in δ18OPO4 is registered, explained by altitude-induced fractionation on meteoric water isotopic composition. The related paleoaltitude change is estimated to be 1200 m, and the uplift could have taken place along the Alpine-Dinaridic orogenic system. © 2014 Geological Society of America.
Magyari E.K.,MTA MTM ELTE Research Group for Paleontology |
Kunes P.,Charles University |
Jakab G.,Szent Istvan University |
Sumegi P.,University of Szeged |
And 4 more authors.
Quaternary Science Reviews | Year: 2014
To characterize Late Pleniglacial (LPG: 26.5-15kacalBP) and particularly Last Glacial Maximum (LGM: 21±2kacalBP) vegetation and climate, fossil pollen assemblages are often compared with modern pollen assemblages. Given the non-analogue climate of the LPG, a key question is how glacial pollen assemblages and thereby vegetation compare with modern vegetation. In this paper we present three LPG pollen records from the Carpathian Basin and the adjoining Carpathian Mountains to address this question and provide a concise compositional characterization of the LPG vegetation. Fossil pollen assemblages were compared with surface pollen spectra from the Altai-Sayan Mountains in southern Siberia. This area shows many similarities with the LPG vegetation of eastern-central Europe, and has long been considered as its best modern analogue. Ordination and analogue matching were used to characterize vegetation composition and find the best analogues. Our results show that few LPG pollen assemblages have statistically significant analogues in southern Siberia. When analogue pairings occur they suggest the predominance of wet and mesic grasslands and dry steppe in the studied region. Wooded vegetation types (continental and suboceanic hemiboreal forest, continental taiga) appear as significant analogues only in a few cases during the LGM and more frequently after 16kacalBP. These results suggest that the LPG landscape of the Carpathian Basin was dominated by dry steppe that occurred outside the river floodplains, while wet and mesic grasslands occurred in the floodplains and on other sites influenced by ground water. Woody vegetation mainly occurred in river valleys, on wet north-facing hillsides, and scattered trees were likely also present on the loess plateaus. The dominant woody species were Larix, Pinus sylvestris, Pinus mugo, Pinus cembra, Picea abies, Betula pendula/. pubescens, Betula nana, Juniperus, Hippophaë rhamnoides, Populus, Salix and Alnus. The pollen records suggest uninterrupted presence of mesophilous temperate trees (Quercus, Ulmus, Corylus, Fagus and Fraxinus excelsior) in the Eastern Carpathian Mountains throughout the LPG. We demonstrate that the LPG vegetation in this area was characterized by increasing grass cover and high frequency of wildfires. We conclude that pollen spectra over represent trees in the forest-steppe landscape of the LPG, furthermore pollen-based quantitative climate reconstructions for the LPG are challenging in this area due to the scarcity of modern analogues. © 2014 Elsevier Ltd.
Finsinger W.,Montpellier University |
Kelly R.,University of Illinois at Urbana - Champaign |
Fevre J.,Montpellier University |
Magyari E.K.,MTA MTM ELTE Research Group for Paleontology
Holocene | Year: 2014
Macroscopic charcoal records can be used to infer spatially explicit reconstructions of past fire history. However, a current deficiency in the charcoal-analysis toolbox has been the lack of a method to consider sampling variability and charcoal-particle area distributions for peak detection with charcoal-area records. We present a screening procedure specific for datasets comprising charcoal numbers and areas to screen the charcoal-area estimates with respect to the count sums. The rationale for screening charcoal-area peaks stems from the observation that although charcoal-area records can be more suitable in a statistical sense for peak detection (e.g. as established by the signal-to-noise index), charcoal-area peaks can be questionable if they are determined by just one or a few larger charcoal particles. Our method begins with a charcoal-area time series analysed by existing methods to identify peaks representing fire episodes. To screen these peaks, the method uses bootstrap resampling of charcoal-particle areas observed in a user-defined subsection of the record around each peak to obtain the range of likely charcoal areas for different counts. Peaks with total area within the likely range of bootstrapped samples (e.g. p > 0.05) are flagged as potentially unreliable, whereas samples with total area significantly greater than expected by chance are deemed robust indicators of past fire events. In an example application of the method to a charcoal record from Lake Brazi, Romania, several peaks failed to pass the screening suggesting that, as for count-based records, unscreened charcoal-area records may include spurious fire episodes and thus potentially underestimate past fire-return intervals. © The Author(s) 2014.
Feurdean A.,Senckenberg Institute |
Feurdean A.,Romanian Academy of Sciences |
Spessa A.,Senckenberg Institute |
Spessa A.,Max Planck Institute for Chemistry |
And 6 more authors.
Quaternary Science Reviews | Year: 2012
Fire is recognized as a critical process with significant impacts on biota and the atmosphere. In this study, 11 micro- and macrocharcoal sedimentary records extracted from peat bogs and lakes at different elevations in the Carpathian region (in Hungary and Romania) were used to explore the patterns and the potential underlying mechanisms in biomass burning in this region during the last 15,000 years. Results from micro-charcoal and macro-charcoal data show similar trends in biomass burning and suggest that the major signal of both charcoal size-fragments relates mainly to local fires. Fire activity was low during the lateglacial, attained maximum values in the early Holocene (11,700-8000 cal. yr BP), become lower than present during the mid-late Holocene (8000-1000 cal yr BP), and increased again over the last 1000 years. The reconstructed spatial trends in biomass burning display different degrees of heterogeneity through time. Generally, there was more spatial similarity in fire activity across the study region during the lateglacial and early Holocene (15,000-8000 cal yr BP), followed by increased spatial heterogeneity from ca 8000 cal yr BP onwards. Biomass burning appears to have been primarily modulated by climate during both the lateglacial and Holocene, through its effect on vegetation productivity and therefore fuel availability (lateglacial), and fuel structure, moisture and flammability (the Holocene). Onsite human activities are likely to have provided an extra ignition source already in the early Holocene. However, evidence suggest that anthropogenic activities have markedly altered the natural trends in biomass burning from about 5500 yr BP (lowlands) and over the last 2000-1000 years (in the mountain environments), by either removing the biomass (in the lowlands) or igniting fire where it seldom occurs naturally (i.e., in the mountain environments). On the other hand, burning activity also appears coincident with significant changes in tree species compositions, indicating that fire has likely acted as a driving factor in forest dynamics. Results also suggest that peat deposits provide a more localized fire record than lakes, and that trends and patterns of change can be different even for sites situated close to each other. © 2012 Elsevier Ltd.
Sumegi P.,University of Szeged |
Sumegi P.,Hungarian Academy of Sciences |
Magyari E.,MTA MTM ELTE Research Group for Paleontology |
Daniel P.,Biogal Pharmavit Rt |
And 2 more authors.
Quaternary International | Year: 2013
According to the findings of a complex sedimentological, geochemical, malacological and pollen study implemented on a core sequence of an alkaline lake (Fehér Lake), interstadials in the SE Great Hungarian Plain were characterized by increased boreal woodland cover during Marine Isotope Stage 2 (MIS 2: 29,700-14,500 cal BP). These interstadials were dated to 26,420-27,970, 23,185-24,880, and 18,810-20,770 cal BP, and correlate well with the Dansgaard-Oeschger (DO) interstadials 2 and 3 and the post LGM warm interval seen in the Greenland ice core oxygen isotope records. Intervening cold phases, on the other hand, were found between 24,880-26,420 and 20,770-23,185 cal BP, correlating with Heinrich event 2 and the LGM. These data overall confirm that millennial scale climate variability during Marine Isotope Stage 2 had profound effect on the terrestrial ecosystems in the continental interior of SE Europe, leading to periodic boreal woodland expansions and contractions and wildfires. © 2012 Elsevier Ltd and INQUA.