engleski

Paleoenvironmental conditions in the Eastern Adriatic recorded in speleothems

Eight caves on seven islands along the eastern Adriatic were investigated and twelve speleothems and seven dripwater samples have been collected in order to reconstruct paleoenvironmental conditions. Dripwater values indicate that the atmospheric conditions over the Atlantic Ocean has greater influence on the isotopic value of the precipitation from Adriatic then Mediterranean atmospheric conditions. High resolution 230Th-234U MC-ICP-MS dating and oxygen and carbon isotopic record of two stalagmites from Strašna peć cave, situated on Dugi otok Island in the central part of the Croatian Adriatic, and two stalagmites from Mala špilja and Vela špilja caves situated on Mljet Island in southern part of the Croatian Adriatic, recorded the period from the Upper Pleistocene (MIS 5) to the Upper Holocene (MIS 1), along with numerous interruptions in growth. The longest record is of stalagmite MSM-1 from Mala špilja cave dated from 119.2 ±3.3 ka to 4±0.6 ka, but deposition was not continuous. δ18O and δ13C measurements conducted on speleothem subsamples from Strašna peć cave and Mala špilja cave, revealed frequent fluctuations and abrupt changes in isotope values expressed in a number of peak values, especially during Holocene. Periods of relatively rapid growth are associated with relatively low δ18O and δ13C values. Therefore, the rapid stalagmite growth and higher δ18O and δ13C values are typical for the period of increased rainfall, increase of soil moisture and higher biogenic activity indicating wetter climate conditions in the Eastern Adriatic. Furthermore, speleothem δ18O and δ13C peak values correspond to significant changes in N.GRIP ice core isotope values and can be compared to O isotope variability associated with Dansgaard- Oeschger interstadials recorded in the Greenland ice cores. Consequently, this study illustrates the impact of Dansgaard-Oeschger, Heinrich and Bond events on the paleoenvironmental changes in the Croatian Eastern Adriatic, confirming the assumption that changes in atmospheric and ocean circulation observed in Greenland and the North Atlantic during the last glacial, influenced the Mediterranean Region and Eastern Adriatic area.

speleothems; isotopes; uranium; paleoenvironment; Eastern Adriatic; Croatia

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