engleski

Environmental changes during Late Pleistocene and Holocene in the karstic lakes along eastern Adriatic coast

Environmental changes can be tracked based on informations from a variety of sources in lakes and lacustrine sediments. These sediments contain paleoenvironmental information that can reflect changes on local or regional scales. Such changes can be better understood by mineralogical and geochemical studies. Observations of the clay minerals were made from three lakes along the eastern part of the Adriatic Sea: Vrana Lake (northern Adriatic), Bokanjačko blato and Baćinska lakes (southern Adriatic). Vertical cores were approximately 7-10 m long. The multyproxy study of the period spanning the transition of the Late Glacial to the Holocene included studies of change in clay composition between glacial and interglacial lake samples assuming transformation processes in the soils from the catchments. Clay mineral assemblages were determined by X-ray diffraction (XRD analysis) in order to model the environment. Dominant clay mineral phases are illite, chlorite and kaolinite. Clay mineral abundances and clay-mineral ratios are used to reconstruct the weathering conditions. In sediments, clay minerals may be originally detrital, diagenetic or neoformed. Mineralogical results are compared with palaeomagnetic-derived time scale. Clay data are further compared with diatom and pollen core material. The evolution of clay derived climate proxies (kaolinite/chlorite ratio) is compared between locations. The cold and dry periods during the glacial times were responsible for physical weathering and thus contribution of higher amounts of chlorite and illite, as they are less sensitive to chemical weathering. The abundance of kaolinite is good indicator of warm and humid interglacial period caused by extensive chemical weathering. Therefore clay mineralogy has become more significant in understanding the changes in paleoclimate conditions and sediment source.

clay minerals; environmental changes; weathering; Late Glacial; Holocene

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