In the capital of Hungary, Budapest, which Ottokar Kadic`´ called 'the capital of the caves', beneath the Rózsadomb (Rose Hill) district of the city, many thermal-karstic caves were discovered based on the lucky coincidence of geologic-hydrologic-speleological fundamentals. At present more than a hundred caves and cave indications are known in this 5-6 km2 area. The hills are made up of Triassic and Eocene carbonate sequences. Five caves are km-size. The corridors are sometimes longer than 100 m, and their walls are often adorned by spherical niches. The total length of the caves exceeds 35 km at present. The galleries of these caves are situated in the Eocene Szépvölgy Limestone. Some galleries and most of the cave indications can be found in the Eocene Buda Marl. The lowest galleries of some caves extend into the Triassic carbonate sequences. Although many paleokarstic cavities and caverns exist in the area the age of the largest caves - according to the preliminary results of investigations still in progress - is some hundreds of thousands of years only, based on the radiometric age of the syngenetic minerals. The exceptional value of the caves are the more than dozen species of minerals (especially the variety and mass of carbonates and sulfates are surprising). Minerals precipitated from warm water, minerals of aerosol formation, as well as recent, still developing minerals of cold water origin can also be found. The caves can be regarded as the fossil source levels of the present-day thermal springs at the banks of the Danube. Their genesis is interpreted as a result of mixing corrosion along tectonic fractures at the level of karst water.
Authors:Attila Demény, Alexandra Németh, Zoltán Kern, György Czuppon, Mihály Molnár, Szabolcs Leél-Őssy, Mihály Óvári, and József Stieber
Determination of the long-term behavior of cave systems and their response to changing environmental conditions is essential for further paleoclimate analyses of cave-hosted carbonate deposits. For this purpose, four actively forming stalagmites were collected in the Baradla Cave where a three-year monitoring campaign was also conducted. Based on textural characteristics and radiocarbon analyses, the stalagmites are composed of annual laminae, whose counting was used to establish age–depth relationships. Fast and slowly growing stalagmites have different stable carbon and oxygen isotope compositions as well as trace element contents that could be attributed to differences in drip water migration pathways. The stable isotope compositions were compared with meteorological data of the last ∼100 years indicating that carbon isotope compositions of the stalagmites may reflect changes in precipitation amount, while oxygen isotope compositions are more related to temperature variations. The combined textural–geochemical–meteorological interpretation lead us to select the isotope record that can best reflect variations in environmental conditions and can be used for further evaluation of the climate–proxy relationships.