Differences in the 14C age, δ13C and δ18O of Holocene tufa and speleothem in the Dinaric Karst
We studied Holocene speleothems and tufa samples collected in numerous caves and rivers in the Dinaric Karst of Croatia, Slovenia, Bosnia and Herzegovina, as well as Serbia and Montenegro. Differences in the formation process of tufa and speleothems are discussed in the context of their isotopic composition ( 14 C, 13 C and 18 O), as well as the chemistry of surface water (rivers, lakes) and drip water (in caves). The physical and chemical parameters monitored in the surface water (tufa precipitation) and drip water (speleothem precipitation) show that more stable conditions accompany speleothem rather than tufa formation. This is particularly obvious in the water temperature variations (2^22‡C in surface water and 7^12‡C in drip water) and in saturation index variation (3^11 in surface water and 1^6 in drip water). The range of 14 C ages recorded by Holocene speleothems (V12 000 yr) is wider by several thousands years than that of Holocene tufa samples (V6000 yr). N 13 C values for tufa samples range from 312x to 36x and for speleothem samples from 312x to +3x reflecting higher soil carbon and/or vegetation impact on the process of tufa than on speleothem formation. The differences in N 18 O values of tufa and speleothem samples from different areas reflect different temperature conditions and differing isotopic composition in the water. The study shows that speleothems from the Dinaric Karst can be used as global palaeoclimatic records, whereas tufa records changes in the local palaeoenvironment. < 2003 Elsevier Science B.V. All rights reserved.