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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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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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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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