A geomorphological and speleological approach in the study of hydrogeology of gypsum karst of Sorbas (SE Spain)

Abstract

The Sorbas massif (Almeria, SE Spain) is one of most karstified gypsiferous areas of the world, with hundreds of dolines and different karst features. In this massif more than 1000 caves have been discovered in an area of about 12 km2. Its Messinian gypsum, deposited in a Neogene intramontane basin, is composed of continuous strata of very pure selenite. The purpose of this research is to identify the main karst geomorphological features and to integrate these data with hydrogeological records for better understanding the role of the karst aquifer in the groundwater recharge of the Aguas River. This study took place in the southern part of the Sorbas gypsum plateau with several steps and multiple field campaigns for geomorphological and geostructural data compilation and to record the different karst forms. Also water samples from the main springs have been collected for geochemical analysis. All field items have been inventoried with corresponding spatial position and compared with the previously existing information. Subsequently, an exhaustive data elaboration was performed leading to the definition of the karst features of the area, rendered by maps. To assess the extent of karstification, the spatial analysis of the cave entrance’s distribution together with structural alignments have been studied.
The cave entrances, a means of access to deep karst, are an expression of discontinuous surface karst phenomenon closely connected with underground drainage that allow to reconstruct the main direction of groundwater flow. This kind of approach can be apply in those areas where rock is exploited, to discern a possible indicator of the effects of the mining and to find the best management conditions that allow the conservation of most of the cavities, the preservation of the recharge basin of the karst system and springs, the minimum affectation to the vadose groundwater flow, the protection of nearby springs and minimizing the visual impact.