José María Calaforra

Gypsum karst features as evidence of diapiric processes in the Betic Cordillera, Southern Spain

In the Triassic evaporite deposits of the Betic Cordillera, halokinesis has played a fundamental role in the morphodynamic evolution of gypsum karst, as evidenced by the morphology and distribution of dolines and poljes, by data obtained from caves, and from the types of water associated with evaporite domes. Distribution patterns of major exokarstic forms display a subcircular array with collapse sinkholes located in the centre of the domes and solution drawdown dolines on the outer limits of the diapiric forms. In addition, the least mineralized waters are situated in association with the caprock gypsum; hypersaline waters, which are also hotter, drain deeper flow systems that flow out at the edges of the halokinetic structures. The morphodynamic and hydrogeological information constitute a valuable tool for the correct interpretation of the tectonic structure of such complex areas.

Evolution of the gypsum karst of Sorbas (SE Spain)

The gypsum karst of Sorbas is developed within Messinian gypsum characterized by an interbedded sequence of selenitic gypsum beds and marls. This geological configuration has led to the development of an interstratal karst in which galleries have developed in the marl levels, but not in the gypsum ones. Up to six cave passage levels have been detected in the gypsum caves following stratification planes between the impervious intercalated marls and the pervious gypsum strata. The explanation for this lies in the hydrogeological history of the area. Initially, the gypsum karst evolved as a multi-layer, semi-confined aquifer under phreatic conditions, enabling the formation of small proto-conduits in the individual gypsum beds, while the intervening marls and clays acted as impervious barriers. During a second stage, after lowering of the piezometric level, vadose conditions were established in which mechanical erosion processes in the intercalated marls and clays became predominant. This genetic duality means that the gypsum karst at Sorbas can be taken as an example of interstratal karstification where the contemporary underground erosion processes and those of karstic evolution should be considered products of the hydrogeological development. The total lowering of the piezometric level during the Quaternary is at least of 120 m in the centre of the basin. Interstratal vadose caves more than 120 m below the surface possess phreatic proto-channels in their upper levels which identify the past phreatic conditions in the genesis of the caves.

Environmental control for determining human impact and permanent visitor capacity in a potential show cave before tourist use

Cave temperature monitoring was carried out in the Cueva del Agua de Iznalloz, Granada, Spain, a cave that has great tourist potential and which has been maintained under natural conditions for over 30 years. The cave temperature under natural conditions was used to identify possible anthropogenic influences, in order to distinguish these from the variations directly related to natural changes. In particular, the relative influence of external weather conditions, thermal modification caused by visitors and the subsequent thermal recovery of the cave were identified. In addition, controlled experiments investigated the effect of two large-scale visits (980 and 2088 visitors day -1 ) to the cave interior, before any tourist activities in the cave were undertaken. Correlation and spectral analyses of time series were used to determine the thermal behaviour of the cave over time. The effect of both mass visits on the air temperature in the interior of the cave was very rapid (2.5 min). The maximum perturbation of air temperature within the cave during the two experiments was after 30 and 70 min. The memory effect for temperature whilst the cave was open to the public was estimated to be 5-6 h, whilst the response to external meteorological changes exceeded one week. A permanent visitor capacity of 53 people ensures that the natural cave temperature can be regained within 4-5 h. The cave can only support small groups of visitors, not the massive visits characteristic of show caves.

Peculiar landforms in the gypsum karst of Sorbas (southeastern Spain)

The gypsum karst of Sorbas is developed in selenitic Messinnian gypsum, the sequence being about 120 meters in depth. Within an outcrop of only 12 km2 there is a great variety of karstic forms, among which the high density of dolines and cavities (over 1000 identified to date) is a notable feature. There also exist many and varied karren landforms, interstratification forms, and tumuli. The karren landforms are strongly developed and are of diverse types. There are also examples of microkarren and nanokarren, such as exfoliation karren or dissolved vacuoles determined by the texture and gypsum crystalline orientation. Some of these forms are unique to gypsum materials and have been described for the first time in this area. The interstratal erosion karst is very well developed due to the marly intercalations existing in the gypsum deposits. This circumstance determined the speleogenesis of the area, with the formation of galleries following the stratification planes. With this structure, the gypsum strata are little altered, and erosion of the marly strata occurs. In some zones, there is an erosive interstratification karst. The tumuli are hollow subcircular domes of the most superficial layer of the gypsum, with sizes varying from a few centimeters to several meters in diameter. Their origin is determined by processes of intercrystalline solution and precipitation, together with the capillary movement of the interstitial water in the gypsum stratum. Their development is related to the abrupt changes in temperature and humidity that are characteristic of semidesert zones such as Sorbas.

Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications

4Centro de Astrobiología (CSIC-INTA). Crta. Ajalvir, 28850. Torrejón de Ardoz, Madrid, Spain (martinezfj@inta.es) Gázquez F., Calaforra J., Forti P., Rull F. and Martínez-Frías J. 2012. Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications. International Journal of Speleology, 41(2), 211-220. Tampa, FL (USA). ISSN 0392-6672. http://dx.doi.org/10.5038/1827-806X.41.2.8

Some examples of gypsum karsts and the more important gypsum caves in Spain

Spain possesses some of the most important examples of gypsum karst in Europe, in terms of the extent and variety of the gypsiferous outcrops. These are divided into gypsum belonging to the Triassic, Palaeogene and Neogene epochs, each of which displays different lithological and structural aspects. Some of Spains most significant gypsum karsts, from the speleological standpoint, are described, and these share a common characteristic of all supporting the development of large caves. Reference is made to the geomorphology, hydrogeology and hydrochemistry of the gypsum karsts of Sorbas, Vallada and Gobantes-Meliones, which provide significant examples of intrastratal karst, speleogenesis by saline groundwater mixing and the influence of carbonate strata, respectively. Finally, brief geomorphological and speleogenetic descriptions of the more significant gypsum caves in Spain are given, together with a list of the longest and deepest gypsum

Siliceous Speleothems and Associated Microbe-Mineral Interactions from Ana Heva Lava Tube in Easter Island (Chile)

Coralloid-type speleothems were recorded on the ceiling of the Ana Heva lava tube in Easter Island (Chile). These speleothems were morphologically, geochemically and mineralogically characterized using a wide variety of microscopy and analytical techniques. They consist dominantly of amorphous Mg silicate and opal-A. Field emission scanning electron microscopy revealed a variety of filamentous and bacillary bacteria on the surface of the Ana Heva coralloid speleothems, including silicified filamentous microorganisms. Among them, intriguing reticulated filaments resemble those filaments documented earlier in limestone caves and lava tubes. The identification of silicified microorganisms on the coralloid speleothems from the Ana Heva lava tube suggests a possible role of these microorganisms in silica deposition.

The present day genesis and evolution of cave minerals inside the Ojo de la Reina Cave (Naica Mine, Mexico)

Ojo de la Reina is the first and the smallest cave intersected at the -290 level in the Naica Mine (Mexico), therefore it was the first cavity in which the lowering of temperature induced by mine ventilation caused condensation over crystals’ surface since 2005. The consequent dissolution of the gypsum crystals and subsequent condensed water evaporation lead to the deposition of several new minerals, among which some highly soluble Mg/Na compounds (bloedite, epsomite, halite, hexahydrite, kieserite, starkeyite). The single available source of Mg and Na ions in this minerogenetic environment is represented by the huge fluid inclusions widespread within the crystals. The condensation occurs mainly along the widened principal exfoliation (010) planes, and allows to an easy and fast opening of the fluid inclusions that consequently drip Mg-rich fluids stored inside them. Finally the evaporation of the relatively small volumes of involved water allows to the development of the high soluble Mg and Na compounds.

Organic matter of fossil origin in the amberine speleothems from El Soplao Cave (Cantabria, Northern Spain)

4Dept. of Mineralogy and Petrology Instituto Andaluz de Ciencias de la Tierra, University of Granada-CSIC, Fuentenueva s/n. 18002, Granada. (agcasco@ugr.es) Gázquez F., Calaforra J.-M., Rull F., Forti P. and García-Casco A. 2012. Organic matter of fossil origin in the amberine speleothems from El Soplao Cave (Cantabria, Northern Spain). International Journal of Speleology, 41(1), 113-123. Tampa, FL (USA). ISSN 03926672. DOI: http://dx.doi.org/10.5038/1827-806X.41.1.12

Hydrogeochemical processes as environmental indicators in drip water: study of the Cueva del Agua (Southern Spain)

INTRODUCTION The hydrodynamic processes and mechanisms involved in rain infiltration and recharge in karst terrains can be identified and quantified by measuring seepage from cave stalactites. Unlike the diffuse recharge that prevails in porous media, the processes and mechanisms involved in recharge of a highly heterogeneous, karstic environment are not easily characterized. A great variety of factors controls the quantity and composition of the water inflow into caves. Climate determines timing and quantity of water input, and the proportion that falls as snow, which could be recycled by evaporation. Climate (and thus altitude and topography) influence vegetation cover, whose development strongly affects the chemistry of the carbonate system and soil properties (Fairchild et al., 2007). The aquifer itself has a complex response