engleski

Radiocarbon dating of tufa in palaeoclimatic studies

Calcareous deposits known as tufa or travertine contain biogenic carbon and are a potential source of geochronologic information. Many dated samples from Karstic regions in Yugoslavia proved that 14^C analyses of tufa can provide reliable data reflecting climatic conditions in the past. Systematic dating of tufa samples revealed two distinct groups of deposits: recent tufa deposits, with a sharp age limit of 6000 ± ; 500 years BP, and old tufa deposits with 'C age ranges from 25, 000 ± ; 2300 years BP to the lowest limit of our 14C dating system (37, O00 years). A histogram based on the initial activity Ao = 0.85 shows the age distribution of randomly sampled tufas vs sample frequency. A time gap between 6000 BP and 23, 000 BP is evident, reflecting cooler climatic conditions. The start of peat deposition is coincident with that of tufa growth in the Holocene. Paleoclimatic implications of tufa growth periods obtained by 14^C dating are as follows: climatic conditions that favor tufa formation at least in karstic regions, are very stringent. Therefore, climatic conditions, such as mean annual temperature and humidity, as well as hydrologic and vegetational conditions, must have been very similar in periods of tufa growth. While recent tufa deposits are coincident with the warm Holocene period, old tufa can be associated with warm interstadials in the Würm.

radiocarbon dating; tufa; paleoclimatology; Plitvice

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