Characterization of tufa from the Dinaric Karst of Croatia: mineralogy, geochemistry and discussion of climate conditions

Tufa deposits from four separate occurrences in the Dinaric Karst of Croatia were characterized with respect to mineralogy, geochemistry and activity of radionuclides. Three of the specimens are of Holocene age, formed during Atlantic, Subboreal and present climate. Two locations (Plitvice Lakes and Krka River) have previously been studied. Two locations (Mrežnica and Slunjčica rivers) have not attracted scientific research yet. The major mineral in tufa is calcite. Minor minerals are quartz and dolomite, depending on location. Geochemistry of selected stream sediments (f <63 μm) from the Dinaric Karst was presented for comparison with tufa. Provided statistically significant number of samples studied, the ratios 238U/226Ra, 238U/232Th and 137Cs may provide tighter constraints on the paleoenvironment. It is suggested to be used in comparison of different world tufas. In general terms it is discussed a hypothesis that relates the occurrence of tufas to atmospheric pCO2 and climate conditions. In addition, the needs for future multidisciplinary research on tufa formation are discussed, because there are several other important parameters dependent on climate, which still have to be studied.