A growing number of studies suggest that cave formation by deep-seated groundwater  (hypogene) is a more common process of subsurface water-rock interaction than previously  thought. Fossil hypogene caves are identified by a characteristic suite of morphological  features on different spatial scales. In addition, mineral deposits (speleothems) may provide  clues about the chemical composition of the paleowater, which range from CO2-rich to  sulfuric acid-bearing waters. This is one of the first studies to examine hypogene cave  formation in dolomite. Kozak Cave is a fossil cave near the Periadriatic Lineament, an area  known for its abundance of CO2-rich springs. The cave displays a number of macro-, mesoand  micromorphological elements found also in other hypogene caves hosted in limestone,  marble or gypsum, including cupolas, cusps, Laughöhle-type chambers and notches. The  existance of cupolas and cusps suggests a thermal gradient capable of sustaining free  convection during a first phase of speleogenesis, while triangular cross sections (Laughöhle  morphology) indicate subsequent density-driven convection close to the paleowater table Notches mark the final emergence of the cave due to continued rock uplift and valley  incision. Very narrow shafts near the end of the cave may be part of the initial feeder system,  but an epigene (vadose) overprint cannot be ruled out. Vadose speleothems indicate that the  phreatic phase ended at least about half a million years ago. Drill cores show no evidence of  carbon or oxygen isotope alteration of the wall rock. This is in contrast to similar studies in  limestone caves, and highlights the need for further wall-rock studies of caves hosted in  limestone and dolomite

Application of the gravity-driven regional  groundwater flow (GDRGF) concept to the  hydrogeologically complex thick carbonate system of the  Transdanubian Range (TR), Hungary, is justified based on  the principle of hydraulic continuity. The GDRGF concept  informs about basin hydraulics and groundwater as a  geologic agent. It became obvious that the effect of  heterogeneity and anisotropy on the flow pattern could be  derived from hydraulic reactions of the aquifer system.  The topography and heat as driving forces were examined  by numerical simulations of flow and heat transport.  Evaluation of groups of springs, in terms of related  discharge phenomena and regional chloride distribution,  reveals the dominance of topography-driven flow when  considering flow and related chemical and temperature  patterns. Moreover, heat accumulation beneath the confined  part of the system also influences these patterns. The  presence of cold, lukewarm and thermal springs and  related wetlands, creeks, mineral precipitates, and epigenic  and hypogenic caves validates the existence of GDRGF in  the system. Vice versa, groups of springs reflect rock–  water interaction and advective heat transport and inform  about basin hydraulics. Based on these findings, a  generalized conceptual GDRGF model is proposed for  an unconfined and confined carbonate region. An interface  was revealed close to the margin of the unconfined and  confined carbonates, determined by the GDRGF and  freshwater and basinal fluids involved. The application  of this model provides a background to interpret manifestations  of flowing groundwater in thick carbonates  generally, including porosity enlargement and hydrocarbon  and heat accumulation.

Cave radon concentration measurements reflect the outcome of a perpetual competition which pitches flux against ventilation and radioactive decay. The mass balance equations used to model changes in radon concentration through time routinely treat flux as a constant. This mathematical simplification is acceptable as a first order approximation despite the fact that it sidesteps an intrinsic geological problem: the majority of radon entering a cavity is exhaled as a result of advection along crustal discontinuities whose motions are inhomogeneous in both time and space. In this paper the dynamic nature of flux is investigated and the results are used to predict cave radon concentration for successive iterations. The first part of our numerical modelling procedure focuses on calculating cave air flow velocity while the second part isolates flux in a mass balance equation to simulate real time dependence among the variables. It is then possible to use this information to deliver an expression for computing cave radon concentration for successive iterations. The dynamic variables in the numerical model are represented by the outer temperature, the inner temperature, and the radon concentration while the static variables are represented by the radioactive decay constant and a range of parameters related to geometry of the cavity. Input data were recorded at Driny Cave in the Little Carpathians Mountains of western Slovakia. Here the cave passages have developed along splays of the NE-SW striking Smolenice Fault and a series of transverse faults striking NW-SE. Independent experimental observations of fault slip are provided by three permanently installed mechanical extensometers. Our numerical modelling has revealed four important flux anomalies between January 2010 and August 2011. Each of these flux anomalies was preceded by conspicuous fault slip anomalies. The mathematical procedure outlined in this paper will help to improve our understanding of radon migration along crustal discontinuities and its subsequent exhalation into the atmosphere. Furthermore, as it is possible to supply the model with continuous data, future research will focus on establishing a series of underground monitoring sites with the aim of generating the first real time global radon flux maps.