Evolution of hot-spring travertine accumulation in Karlovy Vary/Carlsbad (Czech Republic) and its significance for the evolution of Tepla valley and Ohre/Eger rift

摘要

The first set of U-series ages of the hot-spring travertine from the world-famous Karlovy Vary Spa indicates repeated growth of the travertine accumulation followed by its erosion by the Tepla River. The obtained data are important as an estimate of minimum duration of thermal water circulation in Karlovy Vary and in understanding of the river valley evolution during the youngest geological history. The oldest Th-230/U-234 age data (230 +/- 14 ka BP and 155 +/- 7 ka BP) have been obtained for travertine relicts located 22 in above the present-day bottom of the valley. The extensive travertine accumulation located directly on the valley bottom was formed by gradual growth, particularly during the first half of the Weichselian period, between 100 and 50 ka BP. These data show that the valley bottom was at approximately the same elevation as it is today already during the Eemian interglacial. At the end of the Weichselian the central part of the travertine accumulation was downcut by river erosion. During Holocene the new deposition of travertine was concentrated in this wide trench, being likely repeatedly modified by river activity. The travertine accumulation started to be strongly influenced by humans since the Middle Ages. A significant part of it was quarried out for lime production. The accumulation was later covered by buildings, streets and the reinforced course of the Tepla River.