engleski

Ice advance into forested lake environment, evidence of rapid climate change. Case study of Middle Pleistocene Dinaric Mts. foreland, Croatia

Varved lacustrine sediments of the South Velebit Channel coast, eastern Adriatic Sea, comprises fossil macroflora which is the evidence of forested lake banks. Fossil macroflora was taxonomically determined and the leaf morphology was used for paleoclimate reconstruction. Vegetation grew near proglacial lake at the time of advance of major ice tongue from the Velebit Mt. range. The age of studied sediments is determined by U-series dating of secondary calcite in the overlaying lodgement till, providing the minimal age of >350ka. The ice advance is therefore attributed to the MIS 12. Paleoclimate reconstruction yielded paleotemperature values between 5.51 ± 2.86°C and 3.89 ± 2.72°C and mean annual paleoprecipitation of 679 mm. The data reflects the climate conditions in the foreland during the advance of an active ice tongue sometime before the Middle Pleistocene glacial maximum. Lake sediments are varved with presence of dropstones. Varves are complex which indicates differentiated seasons with episodes of temperature oscillations. Leaves are occurring at the base of winter clay laminae. The ice tongue extended at some point all over the lake, eroded the lake bed and glaciotectonically deformed the studied lake sediments. The determined taxa comprise Taxodium sp., Zelkova sp., Quercus sp., Castanea sp., Fagus sp., Liquidambar sp., Tilia sp., Acer cf. rubrum, Pterocarya sp. and Buxus sp. Most of the determined taxa form climax fitocoenosis which means that the vegetation around the lake was zoned and well developed at the time of the ice advance. This indicates climate change so rapid that the vegetation succession didn't have time to compensate for the newly formed conditions. The ice buildup is therefore presumed to last few hundreds of years.

Velebit Mt.; paleo-flora; Middle Pleistocene; paleoclimate

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