ORIGINAL ARTICLE Gypsum karst evolution in a diapir: a case study (Pinoso, Alicante, Spain) Toma ´s Rodrı ´guez-Estrella Antonio Pulido-Bosch Received: 3 September 2008 / Accepted: 9 February 2009 / Published online: 24 February 2009 Ó Springer-Verlag 2009 Abstract Gypsum deposits are highly soluble, and can undergo rapid weathering, especially where water inter- venes, though certain human activities can accelerate the karstification processes. An example of karst formed in gypsum at Pinoso (Alicante, Spain) is analysed to show how human activity has impacted on its evolution. The karst here is associated with a huge diapir in the Triassic terrain that boasts of a large number of highly unusual exokarstic landforms. Here, rock salt has been extracted commercially for over 25 years using solution mining via deep boreholes. The brine extracted contains in excess of 300 g/L; over the whole period, more than 12 million tonnes of salt have been extracted using this method. After preliminary treatment to remove impurities, it travels along a brine pipeline to the coast. The enormous volume of the voids generated have probably favoured the acceleration of certain exokarstic and endokarstic processes. Keywords Karst Á Gypsum Á Triassic Á Halokinesis Introduction Gypsum rocks are very easily karstified due to their high solubility (Klimchouk 1996; Klimchouk et al. 2000; Jeschke et al. 2001; Birk 2002). Some of the resulting landforms are exclusive to these deposits and are not found in limestones or dolomites (Calaforra and Pulido-Bosch, 1999a). Spain boasts of numerous evaporitic outcrops, occupying a total area of around 30,000 km 2 (Calaforra and Pulido-Bosch 1997). The majority of outcrops are associated with Triassic Keuper facies, whilst the domain in which these deposits are most highly developed is the Betic Cordillera. The relationship between landform evolution and gyp- sum dissolution has been identified in both natural (Cooper 1998) and human-induced subsidence processes (Benito et al. 1995; Gutierrez 1996) in the development of alluvial networks (Benito et al. 1998) and in halokinetic effects on the development of fluvial terraces (Mather et al. 1991). The list also includes the reactivation of large-scale Ter- tiary folds due to diapirism in their gypsum cores, which deform Quaternary terraces (Casas et al. 1994), as well as large-scale diapiric processes. In the Betic Cordillera, tectonic structure and lithology have played a significant role in the development of karst in the Triassic outcrops. Gypsum karst morphology depends on a number of geological and hydrogeological factors, including: diapirism and olistostromic movements that modify the initial structures; the presence of aquifers in gypsum discharging at the contemporary base level, deep groundwater flows towards hypersaline springs, mixing of chloride and sulphate waters, certain hydrogeochemical developments such as dolomitization, oxidation of sulphur, and dissolution–precipitation of carbonates or gypsum (Calaforra and Pulido-Bosch 2003). In the case of Pinoso (Alicante), situated within the large geological domain of the Betic Cordillera (Fig. 1), halite extraction from boreholes has led to the formation of salt holes. The main aim of this paper is to identify and describe the human-induced karstification processes, that result from activities in gypsum environments and envi- ronments where hypersoluble salts are associated with T. Rodrı ´guez-Estrella Polytechnic University of Cartagena, 30203 Cartagena, Spain A. Pulido-Bosch (&) Department of Hydrogeology, University of Almerı ´a, Almerı ´a, Spain e-mail: apulido@ual.es 123 Environ Earth Sci (2010) 59:1057–1063 DOI 10.1007/s12665-009-0097-2