Naslov
Isotope records in submarine speleothems from the Adriatic coast, Croatia

Autori
Surić, Maša ; Horvatinčić, Nada ; Suckow, Axel ; Juračić, Mladen ; Barešić, Jadranka

Izvornik
Bulletin de la Société géologique de France (0037-9409) 176 (2005), 4; 363-373

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
karst; submarine speleothem; 14C dating; d13C; d18O; climate change; Adriatic Sea

Sažetak
Isotope studies, using 14C dating, d13C and d18O measurements, were performed at eight speleothems taken from three submerged caves situated along the Eastern Adriatic coast, Croatia. The speleothems were taken from 17 m to 38.5 m depth below mean sea level. The samples consist of four stalagmites and four stalactites in position of growth, covered with marine biogenic overgrowth, and the length of speleothems ranges from ~80 mm to ~190 mm. The youngest (surface) and the oldest (base) layers of speleothems were radiocarbon dated and the 14C ages range from 21, 600 cal BP to >37, 000 yr BP. During that period the global sea level was more than 40 m below the recent one, so presently submerged objects were under the subaerial conditions necessary for speleothem deposition. 14C ages of the youngest layer range from 21, 600 to 32, 200 cal BP for different submerged speleothems. This indicates the time when the speleothem growth ceased, most probably due to flooding of the cave with either fresh or brackish water. Speleothem growth during the Last Glacial Maximum (30-19 kyr ago) and different time of growth cessation for the different speleothem samples suggest that climate change was not the reason for cessation of deposition. Samples for d13C and d18O measurements were taken from six submerged speleothems with sampling distances of ca. 5-10 mm from the surface to the base of speleothems. Most of the d13C values are in the range from 10.5‰ to -8.5‰ , with few exceptions to 6‰ . These values are typical for Dinaric karst, and very different values for marine biogenic overgrowth indicate that no isotopic exchange took place during the submerged period. d18O values range from 6.7‰ to 4.1‰ . A weak correlation between d13C and d18O values indicates possible kinetic isotope fractionation during the calcite precipitation. If the d18O record is interpreted as climatic signal, it suggest similar climatic conditions for the Late Pleistocene and the Holocene, especially no significant differences in temperature and/or moisture transport.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Geologija

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