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001-es BibID:	BIBFORM083342
Első szerző:	Palcsu László (fizikus)
Cím:	Local temperature calibration of carbonate-water oxygen isotope fractionation and clumped isotopes (?47) in a karstic freshwater limestone environment / László Palcsu, Marianna Túri, István Futó, János Kovács, Péter Szabó, Judit Orsovszki, Marjan Temovski, László Rinyu
Dátum:	2019
ISSN:	1029-7006 1607-7962
Megjegyzések:	Oxygen isotope ratios of carbonates are widely used as palaeoclimate indicators since isotope fractionation between the carbonate and the water phase is temperature dependent. The available empirical equationsare reliable for deposits which are precipitated under isotopic equilibrium. However, in many cases, precipitation of abiotic carbonate sediments (flowstones, freshwater limestones, travertines, tufas, etc.) can occur with fast CO2 degassing, which tends to result in a kinetic fractionation of isotope compositions. In karst environments, freshwater limestone is precipitated from cold spring waters as the creek is flowing and the dissolved CO2 is released from the water. This process creates tufa deposits. Our aim is to investigate the suitability of the tufa deposits as a palaeoclimate archive, even if kinetic fractionation plays a significant role during carbonate formation. In Mecsek Mts, Hungary, tufa deposits can be found in karst valleys. We have chosen a karst spring of constant annual temperature of 10.3 ?C. As the water is flowing away from the spring, it is heated up or cooled down by the ambient air, so the annual temperature variation is increasing with the distance from the spring. In 2015, glass plates, as well as temperature loggers, were placed in the water downstream from the spring along with a 200 m long section, so that carbonate could be precipitated onto the glass surface. In 3-4 weeks the glass plates are replaced. Daily average temperatures of the water vary between 0 and 25.6 ?C, while temperatures averaged to the sampling periods vary between 0.8 and 20.1 ?C. The first ? 18Ocarb and clumped isotope results show a significant temperature dependence, although the equations are shifted from those that are reliable to equilibrium circumstances. However, both ? 18Ocarb-T and ?47-T relationships seem to be significant and therefore applicable to the old tufa layers for reconstructing palaeotemperatures.
Tárgyszavak:	Természettudományok Környezettudományok idézhető absztrakt folyóiratcikk
Megjelenés:	Geophysical Research Abstracts. - 21 (2019), p. 8493. -
További szerzők:	Túri Marianna (1988-) (geográfus-geoinformatikus) Futó István (fizikus) Kovács János Szabó Péter Orsovszki Judit Temovski, Marjan Rinyu László (fizikus)
Pályázati támogatás:	GINOP-2.3.2-15-2016-00009 GINOP
Internet cím:	Szerző által megadott URL Intézményi repozitóriumban (DEA) tárolt változat
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