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1.

001-es BibID:BIBFORM080901
Első szerző:Braun Mihály (vegyész, analitikus)
Cím:Using linear discriminant analysis (LDA) of bulk lake sediment geochemical data to reconstruct lateglacial climate changes in the South Carpathian Mountains / M. Braun, K. Hubay, E. Magyari, D. Veres, I. Papp, M. Bálint
Dátum:2013
ISSN:1040-6182
Megjegyzések:A multi-proxy approach is widely used for reconstructing climatic change in alpine lake sediments. This study applied bulk sediment geochemistry to reconstruct lateglacial and early Holocene climatic change in a glacial lake (Lake Brazi, 1740 m a.s.l.) in the Retezat Mts. (South Carpathians, Romania). The lowermost 1 m part of a 4.9-m long sediment core, covering the period between 9950 and 15,750 cal BP, was used for high resolution bulk analysis of major elements (Al2O3, SiO2, TiO2, CaO, MgO, K2O, Na2O, Fe2O3, MnO, SO3). Linear discriminant analysis (LDA) was used to compare a priori classified main chemical groups. Subsamples from the core were priory ordered to "warm" and "cold" groups respectively, according to their age and evidence of cold and warm events in the record, as suggested by proxy correlation with the lateglacial event stratigraphy of North Greenland Ice Core Project (NGRIP). The discriminant function was calculated using concentrations of Al2O3, TiO2, CaO, MgO, K2O, Na2O, Fe2O3, and MnO after log ratio transformation. Loss-on-ignition, silicon and sulphur concentrations were not used for the discriminant analysis, but regarded as comparison proxies for checking up the validity of outputs. Sediments deposited during "cold" and "warm" events were separated significantly by the LDA function; 85.1% of the originally grouped cases were correctly classified under the LDA analysis. The calculated discriminant scores indicated four "cold" and four "warm" events. Sediments ordered into the "warm" group contained larger amounts of organic matter and sulphur, while sediment samples of the "cold" group were characterized by the overall predominance of major oxides bound into inorganic silicates. The discriminant scores showed strong correlation with the NGRIP ?18O data (r = 0.8135) and with the pollen percentage sum of trees and shrubs (r = 0.9460). Loss-on-ignition showed a somehow weaker, but still conclusive linear relationship with the discriminant scores (r = 0.7505). Discriminant analyses of bulk sediment major oxide chemical data may be a useful tool to identify the impact of climatic events upon the nature and composition of materials delivered to a lake basin.
Tárgyszavak:Természettudományok Földtudományok idegen nyelvű folyóiratközlemény külföldi lapban
Megjelenés:Quaternary International. - 293 (2013), p. 114-122. -
További szerzők:Hubay Katalin (1985-) (biológus, környezetkutató) Magyari Enikő (1973-) (biológus) Veres Dániel Papp István (1980-) (vegyész) Bálint Miklós
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2.

001-es BibID:BIBFORM084457
Első szerző:Buczkó Krisztina (biológus)
Cím:Diatom-inferred lateglacial and Holocene climatic variability in the South Carpathian Mountains (Romania) / Buczkó Krisztina, Magyari Enikő Katalin, Braun Mihály, Bálint Miklós
Dátum:2013
Megjegyzések:Climatic and environmental changes were studied using siliceous algae (diatoms and chrysophycean cysts) analyses in a mountain lake in the South Carpathian Mountains for the lateglacial and Holocene. Lake Brazi (1740 a.s.l.) is a small, shallow lake in the Retezat Mountains. According to the basal radiocarbon dating of the core, the lake was formed around 15,750 cal BP and sediment accumulation has been continuous ever since. High resolution diatom analyses were carried out together with loss-on-ignition and biogenic silica measurements. Total epilimnetic phosphorus (TP) concentrations and pH were reconstructed quantitatively. Ten statistically significant zones were distinguished, six of which appeared in the lateglacial and Early Holocene suggesting the instability of diatom assemblages after deglaciation. The uppermost zone covered six thousand years, which suggests that diatom assemblages remained quite stable during the second half of the Holocene. High lake level occurred between 9500 and 9000 cal BP. After 6300 cal BP the lake level gradually increased again until 5800 cal BP. A further increase was detected at 3000 cal BP, while after 1500 cal BP water level decreased. Although there is limited knowledge regarding the environmental constraints of several diatom taxa present in the sequence (e.g. Aulacoseira laevissima), which makes the precise environmental interpretation of the diatom record more difficult, the available data provide an important new insight into the environmental history of Lake Brazi and the Carpathian Mountains. The most remarkable changes in the aquatic ecosystem were observed at 6000 cal BP in the Holocene and 12,800 cal BP, at the onset of the Younger Dryas. Marked changes were also detected at 10,500-10,300; 9800; 9500-9000; 8900-8800; 8300; 6300-5800 and 3100-3000 cal BP.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Quaternary International. - 293 (2013), p. 123-135. -
További szerzők:Magyari Enikő (1973-) (biológus) Braun Mihály (1966-) (vegyész, analitikus) Bálint Miklós
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3.

001-es BibID:BIBFORM079443
Első szerző:Buczkó Krisztina (biológus)
Cím:Diatom-based evidence for abrupt climate changes during the Late Glacial in the Southern Carpathian Mountains / Buczkó Krisztina, Magyari Enikő K., Soróczki-Pintér Éva, Hubay Katalin, Braun Mihály, Bálint Miklós
Dátum:2009
ISSN:1788-2281 1789-3348
Megjegyzések:A high-resolution paleolimnological record from Lake Brazi (TDB-1; 45?23'47"N, 22-54'06"E, 1740 m a.s.l.), a small, glacial lake in the Retezat (South Carpathian Mountains, Romania) provides a sensitive record of the impacts of late glacial climatic change on siliceous algal assemblages. The sequence, ranging from 15,700 cal yr BP to 9500 cal yr BP, suggests that the most significant changes in diatom assemblages took place at 12,800 and 10,400 cal yr BP, when alkaliphilous fragilarioid taxa were replaced by acidophilous diatoms. Altogether eight zones were distinguished with sharp and rapid changes of diatom assemblages. The paper discusses the application of siliceous algae in multi-proxy paleolimnological analyses, demonstrates the advantages and disadvantages of this proxy and presents the story of floristic discovery of unique diatom assemblages, the closest recent analogs of which are found in the arctic region.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény hazai lapban
diatoms
glacial lakes
Megjelenés:Central European Geology. - 52 : 3-4 (2009), p. 249-268. -
További szerzők:Magyari Enikő (1973-) (biológus) Soróczki-Pintér Éva Hubay Katalin (1985-) (biológus, környezetkutató) Braun Mihály (1966-) (vegyész, analitikus) Bálint Miklós
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4.

001-es BibID:BIBFORM079872
Első szerző:Finsinger, Walter
Cím:Holocene fire-regime changes near the treeline in the Retezat Mts. (Southern Carpathians, Romania) / Finsinger Walter, Fevre Jordan, Orbán Ildikó, Pál Ilona, Vincze Ildikó, Hubay Katalin, Birks Hilary H., Braun Mihály, Tóth Mónika, Magyari Enikő K.
Dátum:2018
ISSN:1040-6182
Megjegyzések:To investigate Holocene vegetation and fire-disturbance histories in the treeline ecotone, macroscopic charcoal, plant-macrofossil, and pollen records from two lacustrine sediment records were used. Lake Lia is on the southern slope and Lake Brazi is on the northern slope of the west-east-oriented Retezat Mountain range in the Romanian Carpathians. The records were used to reconstruct Holocene fire-return intervals (FRIs) and biomass burning changes. Biomass burning was highest at both study sites during the drier and warmer early Holocene, suggesting that climate largely controlled fire occurrence. Fuel load also influenced the fire regime as shown by the rapid biomass-burning changes in relation to timberline shifts. Overall, the number of inferred fire episodes was smaller on the northern than on the southern slope. FRIs were also comparatively longer (1000?4000 years) on the northern slope where Picea abies-dominated woodlands persisted around Lake Brazi throughout the Holocene. On the southern slope, where Pinus mugo was more abundant around Lake Lia, FRIs were significantly shorter (80?1650 years). A period of frequent fire episodes occurred around 1900?1300 cal yr BP on the southern slope, when chironomid-inferred summer temperatures increased and the pollen record documents increased anthropogenic activity near the treeline. However, the forest clearance by burning to increase grazing land was subdued in comparison to other European regions.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény külföldi lapban
Treeline
Holocene
Carpathians
Plant macrofossils
Megjelenés:Quaternary International. - 477 (2018), p. 94-105. -
További szerzők:Fevre, Jordan Orbán Ildikó Pál Ilona Vincze Ildikó Hubay Katalin (1985-) (biológus, környezetkutató) Birks, Hilary H. Braun Mihály (1966-) (vegyész, analitikus) Tóth Mónika (1983-) Magyari Enikő (1973-) (biológus)
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5.

001-es BibID:BIBFORM080862
Első szerző:Hubay Katalin (biológus, környezetkutató)
Cím:Dating of pollen samples from the sediment core of Lake St Anne in the East Carpathian Mountains, Romania / Katalin Hubay, Enikő Katalin Magyari, Mihály Braun, Frank Schabitz, Mihály Molnár
Dátum:2016
ISSN:1029-7006 1607-7962
Megjegyzések:Lake St Anne (950 m a.s.l.) is situated in the Ciomadul volcano crater, the youngest volcano in the Carpathians. Aims driving forward the studies there are twofold, one is dating the latest eruption of the Ciomadul volcano and the other is the multi-proxy palaeoenvironmental reconstruction of this region. The sediment of Lake St Anne was sampled several times already, but never reached the bottom of the lake before. During the winter of 2013 at a new core location drilling started at 600 cm water depth and ?nally reached the bottom of the lake sediment at approximately 2300 cm including water depth. As for all multi-proxy studies essential requirement was to build a reliable chronology. Sediments were dated by radiocarbon method. Previous radiocarbon dates were measured on plant macrofossils, charcoal, Cladocera eggs, chironomid head capsules and bulk lake sediments. Lake St Anne has volcanic origin and there is intensive upwelling of CO2it is important to study and take into consideration, whether there is any local reservoir effect at the case of samples where it could be problematic. Furthermore the late part of the sediment section (between 15,000 and 30,000 cal. yr BP) has low organic matter content (less than 2-4%) with scarcity of datable plant macrofossil material. Inthisreviewadifferentfractionofpollensampleswithterrestrialoriginwastestedandstudiedasanovelsample type for the radiocarbon dating. Pollen samples were extracted from the lake sediment cores. This type of organic material could be an ideal candidate for radiocarbon based chronological studies as it has terrestrial source and is present in the whole core in contrast with the terrestrial macrofossils. Although the pollen remains were present in the whole core, in many cases their amount give a challenge even for the AMS technic. Samples were measured with EnvironMICADAS AMS and its gas ion source in the HEKAL laboratory (Debrecen, Hungary). We examine the reliability the radiocarbon dates given from different pollen fractions and their compatibility to the previously measured radiocarbon dates from macrofossil and other dated materials.
Tárgyszavak:Természettudományok Földtudományok idézhető absztrakt
Megjelenés:Geophysical Research Abstracts. - 18 (2016), p. 12260. -
További szerzők:Magyari Enikő (1973-) (biológus) Braun Mihály (1966-) (vegyész, analitikus) Schäbitz, Frank Molnár Mihály (1974-) (fizikus)
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6.

001-es BibID:BIBFORM079873
Első szerző:Hubay Katalin (biológus, környezetkutató)
Cím:Age-depth relationship and accumulation rates in four sediment sequences from the Retezat Mts, South Carpathians (Romania) / Hubay Katalin, Molnár Mihály, Orbán Ildikó, Braun Mihály, Bíró Tamás, Magyari Enikő
Dátum:2018
ISSN:1040-6182
Megjegyzések:This study summarizes the results of radiocarbon dating and age-depth modelling in four mountain lakes (Brazi, Gales, Bucura and Lia) in the Retezat Mountains. Altogether 69 AMS 14C measurements were performed on these deposits, mostly on terrestrial plant macrofossils. In several cases, plant macrofossils, aquatic animal remains (Cladoceran eggs) and bulk sediment were measured from the same depth allowing for the comparison of various sediment components in terms of their dating potential. Age-depth models were developed using both Bayesian modelling with the BACON and smooth spline curve fitting with the CLAM software. In this study Bayesian models are applied to identify outlier 14C dates, while smooth spline models are used to model sediment accumulation age-depth relations, as these are more likely to follow natural deposition time changes of lake sediments. Changes in sediment deposition times (DT) in relation to catchment size and climate are also studied. DT varied considerably in the late glacial (LG) part of the records. The sediment sequence characterised by high deposition rates during the late glacial (DT maximum around 100?110 years cm?1) was defined by small catchment size (Lake Brazi, 6 ha; surface area: 0.5 ha). In contrast, much slower LG sediment deposition in the southern slope lake characterised by large catchment area (Lake Lia, 171 ha, 20 years cm?1), principally reflecting strong erosion in these catchment areas at times when vegetation cover was scarce. Holocene was characterised again by variable DT values, but only Lake Gales showed extreme values: 62?110 years between 10,900 and 6050 cal yr BP, followed by much slower sediment deposition in the last 6000 years (av. 29 years cm?1). Generally, sediment deposition times were largely dependent on the stability and vegetation cover of the slope in the case of high altitude deep lakes, while lower altitude, shallow lakes showed slower sediment deposition time in the early and mid-Holocene, when summer insolation was higher than today. This reflects that in these shallow lakes in-lake organic production probably increased with summer insolation, which was a significant driver in the rate of deposition.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény külföldi lapban
AMS 14C dating
Glacial lake sediments
Late glacial
Holocene
Carpathians
Megjelenés:Quaternary International. - 477 (2018), p. 7-18. -
További szerzők:Molnár Mihály Orbán Ildikó Braun Mihály (1966-) (vegyész, analitikus) Bíró Tamás Magyari Enikő (1973-) (biológus)
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7.

001-es BibID:BIBFORM073714
Első szerző:Hubay Katalin (biológus, környezetkutató)
Cím:Holocene environmental changes as recorded in the geochemistry of glacial lake sediments from Retezat Mountains, South Carpathians / Hubay Katalin, Braun Mihály, Buczkó Krisztina, Pál Ilona, Veres Daniel, Túri Marianna, Biró Tamás, Magyari Enikő
Dátum:2018
ISSN:1040-6182
Megjegyzések:Sediment cores obtained from two deep (>15?m) glacial lakes were analyzed in context of terrestrial vegetation development and in-lake processes from the Retezat Mountains (Southern Carpathians, Romania). Only the Holocene parts were chosen for study for testing what is the connection between geochemical changes and biotas around and in the lakes. The lakes are situated at slightly different altitudes on the northern (Lake Gales, 1990 m a.s.l.) and southern slope (Lake Bucura, 2040 m a.s.l.), respectively. Changes in geochemical composition were relatively low amplitude during the studied period (10,300?1790 and 10,300?695?cal?yr BP) in both lakes, but the applicability of enrichment factor (EF) for geochemical elements and diatom ecological traits (guilds) in paleoecological reconstruction were demonstrated in this paper. The main changes have been observed at ca. 10,670?9000, 6500 and 3100?cal?yr BP in geochemistry, vegetation and siliceous algal assemblages. Catchment soil stabilization was apparent from ?9000?cal?yr BP onwards, in-lake and terrestrial productivity was the highest between 9000 and 6500?cal?yr BP and human impact became the dominant driver in both terrestrial vegetation and sediment geochemical changes and in-lake processes over the last ?3400 years in both lakes. The geochemical record displayed frequent erosional events within the Holocene. The strongest soil erosions clustered around 6500?7400 and 3200-900?cal?yr BP.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény külföldi lapban
holocén
környezetváltozás
geokémia
szediment
Megjelenés:Quaternary International. - 477 (2018), p. 19-39. -
További szerzők:Braun Mihály (1966-) (vegyész, analitikus) Buczkó Krisztina (1962-) (biológus) Pál Ilona Veres Dániel Túri Marianna (1988-) (geográfus-geoinformatikus) Biró Tamás Magyari Enikő (1973-) (biológus)
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8.

001-es BibID:BIBFORM084481
Első szerző:Karátson Dávid (földrajz-biológia tanár)
Cím:Morphometrical and geochronological constraints on the youngest eruptive activity in East-Central Europe at the Ciomadul (Csomád) lava dome complex, East Carpathians / Karátson Dávid; Telbisz Tamás; Harangi Szabolcs; Magyari Enikő; Dunkl István; Kiss Balázs; Jánosi Csaba; Veres Dániel; Braun Mihály; Fodor Emőke; Biró Tamás; Kósik Szabolcs; Hilmar von Eynatten; Ding Lin
Dátum:2013
ISSN:0377-0273
Megjegyzések:The timing of Late Pleistocene volcanic activity of the Ciomadul (Csomád) dacitic lava dome complex, site of the youngest eruptions in the Carpathians, has been constrained by morphometric analysis and radiometric chronology. Peléan domes and asymmetric domes/coulées built up the volcano, including the central edifice that hosts the youngest twin craters ofMoho₀s (Mohos) peat bog and lake St. Ana (Szent Anna). A comparative digital elevationmodel (DEM)-basedmorphometric analysis of lava domes (29worldwide examples including 5 domes from Ciomadul) shows that it is themean slope of the upper dome flank that correlates best with age. Although the logarithmic relationship is only moderately strong (R=0.80), slope characteristics of the Ciomadul domes fit to those of 10?100 ka old domes. These young ages contradict the previous K/Ar dates giving as old as 1 Ma ages on a number of domes, but are supported by ongoing U?Pb and (U?Th)/He zircon dating. The latter methods constrain the whole volcanic activity to the past 250 ka and the emplacement of most lava domes within the period of 150?100 ka. The volcanism at Ciomadul produced alternating effusive and explosive eruptions including lava dome collapses and successive crater formations. The latest, possibly subplinian explosive event formed the wellpreserved St. Ana crater. Radiocarbon dating of organic remains from a sediment core that reached 11 m into the lacustrine infill of St. Ana suggests that the crater was formed prior to 26,000 years BP
Tárgyszavak:Természettudományok Földtudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Lava dome morphometry
DEM analysis
Carpathian volcanism
U-Pb and (U-Th)/He geochronology
Paleolimnology
Megjelenés:Journal Of Volcanology And Geothermal Research. - 255 : 1 (2013), p. 43-56. -
További szerzők:Telbisz Tamás Harangi Szabolcs (1962-) (geokémikus, vulkanológus) Magyari Enikő (1973-) (biológus) Dunkl István Kiss Balázs Jánosi Csaba Veres Dániel Braun Mihály (1966-) (vegyész, analitikus) Fodor Emőke Biró Tamás Kósik Szabolcs Eynatten, Hilmar von Ding, Ling
Pályázati támogatás:Hungarian National Research Funds T68587
Egyéb
Hungarian National Research Funds NF101362
Egyéb
SOPHRD 2007?2013 project no./POSDRU/89/1.5/S/60189
Egyéb
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9.

001-es BibID:BIBFORM032057
Első szerző:Korponai János (biológus)
Cím:Cladocera response to Late Glacial to Early Holocene climate change in a South Carpathian mountain lake / János Korponai, Enikő Katalin Magyari, Krisztina Buczkó, Sanda Iepure, Tadeusz Namiotko, Dániel Czakó, Csilla Kövér and Mihály Braun
Dátum:2011
ISSN:0018-8158
Megjegyzések:This study explores changes in cladocerancomposition in a high mountain lake of the Retezat(Lake Brazi), the South Carpathian Mountains ofRomania, during the Late Glacial-Early Holocene(14,500-11,600 cal. yr. BP) transition using a paleolimnologicalapproach. The lake had a species poorcladoceran community throughout this period. Daphnialongispina, Chydorus sphaericus and Alona affiniswere the most common, showing marked fluctuations in their relative abundances through time. Distinctfaunal response to warming at the Younger Dryas(YD)/Preboreal transition was recorded by increasingfossil densities and distinct community compositionchange: Alona affinis became dominant while numbersof Chydorus sphaericus dramatically decreased.In the Early Holocene, the productivity of Lake Braziseem to have increased as reflected by higher numbersof Cladocera due to appearance of new species (Alonarectangula, A. quadrangularis and A. guttata) whichare common in productive waters. Significant negative correlation was found between average dorsal length of daphnid ephippia and the NGRIP d18O isotopevalues. Given the absence of fish predation, changes inDaphnia ephippia size were taken to indicate climaticchange: larger ephippium size inferred cold conditionsduring the Late Glacial, while smaller size reflectedclimate warming during the Early Holocene. Weconclude that Cladocera fossils are good indicators ofclimatic change that happened during the transitionfrom the Late Glacial to the Holocene. We found thatclimatic conditions can be tracked either by sizedistribution of Daphnia ephippia (larger ephippiumsize under colder climate) and/or by communitychange of cladocerans.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény külföldi lapban
Cladocera remains
Chydorids
Climate change
Mountain lake
Romania
Megjelenés:Hydrobiologia. - 676 : 1 (2011), p. 223-235. -
További szerzők:Magyari Enikő (1973-) (biológus) Buczkó Krisztina (1962-) (biológus) Iepure, Sanda Namiotko, Tadeusz Czakó Dániel Kövér Csilla Braun Mihály (1966-) (vegyész, analitikus)
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10.

001-es BibID:BIBFORM095733
Első szerző:Magyari Enikő (biológus)
Cím:Holocene paleohydrology and environmental history in the South Harghita Mountains, Romania : Holocén hidrológiai és környezeti változások a romániai Dél-Hargita-hegységben / Magyari Enikő, K. Buczkó Krisztina, Jakab Gusztáv, Braun Mihály, Szántó Zsuzsa, Molnár Mihály, Pál Zoltán, Karátson Dávid
Dátum:2006
Megjegyzések:A tanulmány az erdélyi Csornád-hegycsoport fiatal krátertavának, a Szent Anna-tónak a holocén üledékfeldolgozását tárgyalja. Pollen, növényi makrofosszflia, szilíciumvázas alga- és nyomelemvizsgálatok segítségével rekonstruáltuk a holocén környezetváltozásokat és a tó vízszintjének ingadozásait. Vizsgálataink alapján a kráterben mintegy 9800 és 8800 kai. BP évek közt sekély oligotróf tó alakult ki, melyet 8800 évvel ezelőtt a vízszint csökkenését követően tőzegmohaláp nőtt be. A szárazföldi vegetációban a mogyoró (Corylus avellana) dominanciája jellemezte ezt az időszakot. A diatóma- és makroflóra változásai alapján 7050 évtől a tó vízszintje fokozatos emelkedésnek indult és egészen 5500 évig sekély, vízimohákban gazdag oligotróf tavi állapot alakult ki. 5500 évvel ezelőtt a vízsszint jelentős emelkedése egybeesett a szárazföldi vegetációban a gyertyán (Carpinus betulus) terjedésével. A vízszint emelkedését a tó produktivitásának növekedése és gazdag makrofiton vegetáció kialakulása kísérte. A holocén folyamán a legmélyebb tavi állapot a bükk (Fagus sylvatica) dominanciájával egyidőben, kb. 2700 és 700 évek közt alakult ki. A tópartot a makrofosszflia vizsgálatok alapján a kora-holocéntől kezdődően lucfenyves (Picea abies) erdősáv borította mely függetlenül a zonális erdőtársulások változásaitól mindvégig fennmaradt a tómedence hűvös mikroklímájának köszönhetően.
Tárgyszavak:Természettudományok Földtudományok idegen nyelvű folyóiratközlemény hazai lapban
folyóiratcikk
Holocene
palaeoecology
Lake Saint Ana
Romania
holocén
paleoökológia
Szent Anna-tó
Románia
Megjelenés:Földtani Közlöny. - 136 : 2 (2006), p. 249-284. -
További szerzők:Buczkó Krisztina (1962-) (biológus) Jakab Gusztáv Braun Mihály (1966-) (vegyész, analitikus) Szántó Zsuzsa Molnár Mihály (1974-) (fizikus) Pál Zoltán Karátson Dávid (1964- ) (földrajz-biológia tanár)
Pályázati támogatás:D45947
OTKA
T043664
OTKA
T43078
OTKA
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11.

001-es BibID:BIBFORM084456
Első szerző:Magyari Enikő (biológus)
Cím:A 13,600-year diatom oxygen isotope record from the South Carpathians (Romania): Reflection of winter conditions and possible links with North Atlantic circulation changes / Magyari Enikő Katalin, Demény Attila, Buczkó Krisztina, Kern Zoltán, Vennemann T., Fórizs István, Vincze Ildikó, Braun Mihály, Kovács István János, Udvardi Beatrix, Veres Dániel
Dátum:2013
ISSN:1040-6182
Megjegyzések:This study provides a continuous lateglacial and Holocene record of diatom silica oxygen isotope changes (?18ODIAT) in a subalpine lake sediment sequence obtained from the Retezat Mts (Taul dintre Brazi, 1740 m a.s.l.). This through-flow, shallow, high-altitude lake with a surface area of only 0.4 ha has short water residence time and is predominantly fed by snowmelt and rainwater. Its ?18ODIAT record principally reflects the oxygen isotope composition of the winter and spring precipitation, as diatom blooms occur mainly in the spring and early summer. Hence, changes in ?18ODIAT are interpreted as seasonal scale changes: in the amount of winter precipitation. Low oxygen isotope values (27-28.5?) occurred during the lateglacial until 12,300 cal BP, followed by a sharp increase thereafter. In the Holocene ?18ODIAT values ranged from 29 to 31? until 3200 cal BP, followed by generally lower values during the late Holocene (27?30?). Short-term decreases in the isotopic values were found between 10,140-9570, 9000?8500, 7800?7300, 6300?5800, 5500?5000 and at 8015, 4400, 4000 cal BP. After 3200 cal BP a decreasing trend was visible with the lowest values between 3100?2500 and after 2100 cal BP The general trend in the record suggests that contribution of winter precipitation was generally lower between 11,680 and 3200 cal BP, followed by increased contribution during the last millennia.
Tárgyszavak:Természettudományok Kémiai tudományok idegen nyelvű folyóiratközlemény külföldi lapban
folyóiratcikk
Megjelenés:Quaternary International. - 293 (2013), p. 136-149. -
További szerzők:Demény Attila Buczkó Krisztina (1962-) (biológus) Kern Zoltán Vennemann, Torsten Fórizs István Vincze Ildikó Braun Mihály (1966-) (vegyész, analitikus) Kovács István János Udvardi Beatrix (Budapest) Veres Dániel
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DOI
Intézményi repozitóriumban (DEA) tárolt változat
Borító:

12.

001-es BibID:BIBFORM079444
Első szerző:Magyari Enikő (biológus)
Cím:Radiocarbon chronology of glacial lake sediments in the Retezat Mts (South Carpathians, Romania): a window to Late Glacial and Holocene climatic and paleoenvironmental changes / Magyari Enikő K., Braun Mihály, Buczkó Krisztina, Kern Zoltán, László Péter, Hubay Katalin, Bálint Miklós
Dátum:2009
ISSN:1788-2281 1789-3348
Megjegyzések:As a first piece in a series of Late Quaternary paleoecological studies on the glacial lake sediments of the Retezat Mountains, this study discusses radiocarbon chronology and sediment accumulation rate changes in two sediment profiles in relation to lithostratigraphy, organic content, biogenic silica and major pollenstratigraphic changes. A total of 25 radiocarbon dates were obtained from sediments of two lakes, Lake Brazi (TDB-1; 1740 m a.s.l.) and Lake Gales (Gales-3; 1990 m a.s.l.). Age-depth modeling was performed on TDB-1 using calibrated age ranges from BCal and various curve-fitting methods in psimpoll. Our results suggest that sediment accumulation began between 15,124?15,755 cal yr BP in both lakes and was continuous throughout the Late Glacial and Holocene. We demonstrated that local ecosystem productivity showed delayed response to Late Glacial and Early Holocene climatic changes in the subalpine and alpine zones most likely attributable to the cooling effect of remnant glaciers and meltwater input. However, regional vegetation response was without time lag and indicated forestation and warming at 14,450 and 11,550 cal yr BP, and cooling at ca. 12,800 cal yr BP. In the Holocene one major shift was detected, starting around 6300 cal yr BP and culminating around 5200 cal yr BP. The various proxies suggested summer cooling, shorter duration of the winter ice-cover season and/or increasing size of the water body, probably in response to increasing available moisture.
Tárgyszavak:Természettudományok Környezettudományok idegen nyelvű folyóiratközlemény hazai lapban
folyóiratcikk
Late Glacial
radiocarbon dating
loss-on-ignition
pollen
glacial lake sediments
rapid climate change
Megjelenés:Central European Geology. - 52 : 3-4 (2009), p. 225-248. -
További szerzők:Braun Mihály (1966-) (vegyész, analitikus) Buczkó Krisztina (1962-) (biológus) Kern Zoltán László Péter Hubay Katalin (1985-) (biológus, környezetkutató) Bálint Miklós
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