engleski

Tufa barriers and laminated carbonate incrustations in Krka National Park, Croatia, as modern climate indicators

Recent carbonate precipitates (tufa and laminated incrustations) formed in the Krka national Park (Central Dalmatia, Croatia) were investigated. Stable isotope composition of carbonate precipitates (&#948; 13C, &#948; 18O), as well as river water chemical and isotopic composition (Ca2+, Mg2+, pH, total alkalinity, &#948; 18O, &#948; D, &#948; 13C of dissolved inorganic carbon) werw analysed. Saturation indices for carbonate minerals (calcite, aragonite, dolomite) revealed that supersaturation (SI<0.3) was not necessarily sufficient for chemical precipitation of calcite. However, precipitation can take place in turbulent water at cascades, waterfalls, and mechanical burdens or in microenvironments created by plants. Laminated precipitate was formed from the spray on the ceiling of a concrete tunnel diverting the water masses to the Jaruga power plant. Three subsequently warmer period (1960-1970, 1970-1990 and from 1990 on) can bi identified from the &#948; 18O record, while the interpretation of carbon isotope signal is more debatable ; higher &#948; 13C values can be attributed to increased biological productivity or to a change in input of soil-derived CO2.

tufa; Krka River; Stable isotope; Climate indicators

Geochimica et Cosmochimica Acta (ISSN 0016-7037) 66 (2002) (15A)