4.7 Article

Paleotemperature reconstructions using speleothem fluid inclusion analyses from Hungary

期刊

CHEMICAL GEOLOGY
卷 563, 期 -, 页码 -

出版社

ELSEVIER
DOI: 10.1016/j.chemgeo.2020.120051

关键词

Speleothem; Paleotemperature reconstruction; Fluid inclusion; Calcite; Stable isotope composition; Clumped isotope

资金

  1. National Research, Development and Innovation Office, Hungary [OTKA 101664, PD 121387]
  2. Hungarian Academy of Sciences (NANOMIN project) [KEP-8/2018, ELKH KEP-1/2020]
  3. European Union
  4. State of Hungary
  5. European Regional Development Fund [GINOP-2.3.2-15-2016-00009]
  6. Science Vanguard Research Program of the Ministry of Science and Technology (MOST) [109-2123-M-002-001]
  7. National Taiwan University [109L8926]
  8. Higher Education Sprout Project of the Ministry of Education, Taiwan ROC [108L901001]

向作者/读者索取更多资源

The combined use of stable isotope compositions of speleothem carbonate and inclusion-hosted water shows great potential in paleotemperature reconstructions. Different approaches were evaluated for hydrogen and oxygen isotope measurements of inclusion-hosted water and host calcite. The results indicated that hydrogen isotope data may yield realistic temperatures under certain conditions.
The combined use of the stable isotope compositions of speleothem carbonate and inclusion-hosted water presents great potential in paleotemperature reconstructions, due to the various temperature-dependent isotope fractionations detected in cave systems and their environment. This paper evaluates the applicational possibilities of hydrogen and oxygen isotope measurements of inclusion-hosted water and its host calcite, in three different approaches: i) direct determination of calcite-water oxygen isotope fractionation by measuring inclusion water and carbonate compositions, ii) calculation of water oxygen isotope composition from hydrogen isotope data and of temperature from the inferred calcite-water fractionation, and iii) calculation of formation temperature from measured hydrogen isotope data and its temperature dependence in the modern precipitation water. Fluid inclusion oxygen and hydrogen isotope compositions as well as calcite oxygen isotope compositions were determined for five speleothem occurrences in Hungary. Although the background processes are not resolved, calculations involving measured calcite and water oxygen isotope compositions yielded unrealistic paleotemperatures, likely because of syn-formation isotope fractionation processes and diagenetic alterations. The hydrogen isotope data may yield realistic temperatures, provided that long-term isotopic composition temperature relationships are known and the stable hydrogen isotope composition of the precipitation waters in the study area is temperature-controlled. Winter half-year and annual isotope-temperature relationships (delta H-2/T gradients) were calculated using multidecadal isotope composition records from the Global Network of Isotopes in Precipitation (GNIP), gridded surface temperatures, and precipitation amounts from the E-OBS 21.0e database. The calculations yielded a paleotemperature record for the last similar to 250 ka, with average precisions ranging from +/- 0.6 degrees C for interglacial to +/- 2.4 degrees C for glacial periods. Clumped isotope analyses of cave-hosted flowstones support the inferred formation temperatures based on gradients, while detection of kinetic fractionations by combined hydrogen and oxygen isotope analyses of calcite and inclusion water lead to filtering clumped isotope (Delta(47)) data and more coherent Delta(47)-temperature relationships.

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