Naslov
Scientific research in the Cave system Lukina jama – Trojama (-1421) on the Velebit karst massif (Croatia)

Autori
Paar, Dalibor ; Stroj, Andrej ; Buzjak, Nenad ; Bakšić, Darko ; Lacković, Damir ; Ujević Bošnjak, Magdalena ; Radolić, Vanja ; Kljajo, Dubravka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
21th International Karstological School Guide book & Abstracts / Otoničar, Bojan ; Gostničar, Petra ; Gabrovšek, Franci - Postojna : Inštitut za raziskovanje krasa ZRC SAZU, 2013, 77-77

Skup
21th International Karstological School

Mjesto i datum
Postojna, Slovenija, 10.06.2013. - 14.06.2013

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
geology ; hydrology ; cave climate ; radon ; speleology ; Dinaric karst ; Croatia

Sažetak
The objective of this study is to present the first results of scientific research conducted in the 1421 m deep cave system Lukina Jama - Trojama during 2010 and 2011. The cave is situated in the area of Hajdučki kukovi in Northern Velebit National Park (Croatia) and is the deepest cave system in the Dinaric karst. Deep pits of Mt. Velebit provide excellent way of gathering new insights on the geology, geomorphology, hydrology, physical processes and other properties of karst underground. Therefore, the aim of scientific research is to gather as much information on those properties. In situ measurements of microclimate parameters and radon concentrations were performed at 20 measuring points for one year. The air temperature in the cave ranges from 0 °C in the upper part where permanent snow and ice are noted, to 5 °C at a depth of 1368 m next to lake/siphon. Two temperature gradients were detected. The change of sign of temperature gradient is 100 m deeper than in 1026 m deep Cave system Velebita that was previously explored in Northern Velebit. The difference is probably due ice and snow dynamics that influenced microclimate parameters to a depth of 200 m. Mean radon concentrations changed with depth, from 200–600 Bq/m3 in the upper cave sections, up to 1139 Bq/m3 in the lower sections. This increase is in correlation with the partial pressure of carbon dioxide. Microclimate conditions below a depth of 220 m to the bottom are very stable, so speleothems are good candidates for further paleoclimate investigation. Lithostratigraphic and chronostratigraphic research was conducted. Geological profile of the Velebit Mt. underground was reconstructed based on the research results. At that time hydrological research was also taken up in the bottom syphon of the Cave. In the period of one year water level, temperature and electrical conductivity were measured in the entrance pool of the syphon. Measured data provide insight in the hydrogeological properties of the massif in its central part, between main sinkholes on the east and coastal springs on the west. Water in the pit is circumneutral to slightly alkaline, with pH ranging from 7.65 to 8.27. Temperature ranges from 0.8 to 4.7°C. Observed changes of water conductivity and TDS through the pit reflect impact of the lithology, geomorphology and mixing of the waters from different flows on the water chemistry. According to the analyses of major cations and anions for three water samples from the pit, concentration of Ca2+ largely exceeds that of Mg2+, Na+ and K+. The predominant anion is HCO3- so water in the cave is Ca-HCO3 type as a result of dissolution of carbonate rocks - limestone. Even if dolomite can be present too due to short water-rock interaction time Mg concentration are low. However, slightly higher Mg concentration was observed in the sample from -1368 m which present syphon and longer water-rock interaction period.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Geografija

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