New perspectives on water chemistry classification of travertine/tufa

If travertine/tufa is a solidified carrier of information records, karst water is the most important transport carrier of such information. In this study, we investigate the water chemistry of partial travertine/tufa around the world. Based on the better linear relationship between Ca 2+ and HCO 3 − , the classification view of Ca 2+ -biased and HCO 3 − -biased types is proposed. Ca 2+ -biased is defined as a high Ca 2+ concentration compared to the theoretical value of the chemical formula for Ca(HCO 3 ) 2 , while HCO 3 − -biased is defined as a high HCO 3 − concentration compared to the theoretical value of the chemical formula for Ca(HCO 3 ) 2 . By comparing the concentrations of Ca 2+ and HCO 3 − in hot and cold spring travertine/tufa around the world, the relationship between Ca 2+ -biased and HCO 3 − -biased type is described, providing reference for the classification research of travertine/tufa. • Classify the world travertine/tufa into two types: Ca 2+ -biased and HCO 3 − -biased. • All cold springs travertine/tufa are HCO 3 − -biased. • Karst water carries information of the travertine/tufa depositional environment.