International Journal of Speleology 43 (2) 125-142 Tampa, FL (USA) May 2014 Available online at scholarcommons.usf.edu/ijs/ & www.ijs.speleo.it International Journal of Speleology Off icial Journal of Union Internationale de Spéléologie Speleothems in Cova des Pas de Vallgornera: their distribution and characteristics within an extensive coastal cave from the eogenetic karst of southern Mallorca (Western Mediterranean) Antoni Merino1*, Joaquín Ginés2, Paola Tuccimei3, Michele Soligo3, and Joan J. Fornós4 1 Grup Espeleològic de Llubí, Illes Balears, Spain 2 Federació Balear d’Espeleologia, Palma, Illes Balears, Spain 3 Università “Roma Tre”, Dipartimento di Scienze, Sezione di Scienze Geologiche, Largo San Leonardo Murialdo 1, 00146 Roma, Italy 4 Departament de Ciències de la Terra, Universitat de les Illes Balears, Ctra. Valldemossa km 7.5, 07122 Palma, Illes Balears, Spain Abstract: The abundance and variety of speleothems are undoubtedly among the remarkable features of Cova des Pas de Vallgornera, the longest cave system in Mallorca Island developed in the eogenetic karst of its southern coast. Due to the monotonous carbonate lithology of the area, most of the speleothems are composed of calcite and in a few cases aragonite, although other minerals are also represented (e.g., gypsum, celestine, barite). However, in spite of the rather common mineralogy of the speleothems, its distribution results strongly mediated by the lithologic and textural variability linked to the architecture of the Upper Miocene reefal rocks. Apart from a vast majority of speleothem typologies that are ubiquitous all along the cave system, some particular types are restricted to specific sections of the cave. In its landward inner passages, formed in the low permeability back reef facies, a great variety of speleothems associated to perched freshwater accumulations stands out, as well as some non frequent crystallizations like for example cave rims. On the other hand, the seaward part of the cave (developed in the very porous reef front facies) hosts conspicuous phreatic overgrowths on speleothems (POS), which are discussed to show their applications to constrain sea level changes. The factors controlling the distribution of speleothems found in Cova des Pas de Vallgornera are discussed along the paper, focusing the attention on the lithologic, hydrogeologic, and speleogenetic conditionings; at the same time some uncommon speleothems, not found in any other cave in Mallorca, are also documented from this locality. Finally, a cognizant effort has been undertaken to illustrate with photographs the most remarkable speleothem types represented in the cave. Keywords: speleothems, carbonate crystallizations, phreatic overgrowths, coastal karst, southern Mallorca Received 5 October 2013; Revised 19 January 2014; Accepted 28 February 2014 Citation: Merino A., Ginés J., Tuccimei P., Soligo M. and Fornós J.J., 2014. Speleothems in Cova des Pas de Vallgornera: their distribution and characteristics within an extensive coastal cave from the eogenetic karst of southern Mallorca (Western Mediterranean). International Journal of Speleology, 43 (2) 125-142. Tampa, FL (USA) ISSN 0392-6672 http://dx.doi.org/10.5038/1827-806X.43.2.3 INTRODUCTION this peculiar profusion and exhibition of speleothems was first highlighted (Merino, 2000). But it is not until The importance of Cova des Pas de Vallgornera is the unexpected exploration breakthrough of 2004, not only related to the extension attained by the cave when the hitherto unknown Descobriments 2004 itself (over 74 km of development), but also for the series are discovered, that a full awareness for the exceptional richness, striking variety, and abundance spectacular display of speleothems is built (Merino et of speleothems. This wide exhibition of carbonate al., 2006). The discovery of abundant rimstone dams crystallizations is a common occurrence in Mallorcan (gours) hosting a great number of other subaqueous karst areas (Ginés, 1995; Merino et al., 2011), but types like shelfstones, cave rafts, cave cups, pool spar certainly this cave represents an exceptional case and, for instance, the existence of large areas of the regarding this topic. As early as 2000, with the discovery cave covered in numerous capillary crystallizations ― and exploration of the Noves Extensions series (Fig. 1), like filiform and vermiform helictites― were showing *[email protected] 126 Merino et al. a well-organized distribution of certain groups of the different sectors, main galleries, and chambers, a speleothems. The finding of uncommon typologies, comprehensive article including a detailed description like cave rims, cave bubbles, pool fingers, and U-loops of the cave is also published in this issue (Merino et (to mention just a few of them) greatly enlarged the al., 2014). The totality of photographs included in types of speleothems represented in Cova des Pas de the paper has been performed by one of the authors Vallgornera (Merino, 2007b, 2008; Merino & Fornós, (AM) with the helpful collaboration of cavers from 2010a), converting this cave in a unique locality several clubs integrated within the Federació Balear within the Mallorca’s endokarst. d’Espeleologia. Owing to the littoral character of the cave system, a special mention must be addressed to phreatic FACTORS THAT CONTROL THE overgrowths on speleothems (POS). These carbonate DISTRIBUTION OF SPELEOTHEMS IN THE encrustations have grown at the current sea-controlled STUDIED CAVE water table (Tuccimei et al., 2010), recording in the same way ancient sea level positions (Dorale et al., Mallorca is a mid-latitude island (39ºN) located in 2010; Ginés et al., 2012b). The data supplied by a bioclimatic setting typically Mediterranean, with an the coastal phreatic speleothems from this cave are annual average temperature of 16.6ºC and a mean discussed in order to constrain sea level history precipitation value near 600 mm/yr (Guijarro, 1995); during Pleistocene. Apart from the POS investigations, rainfall is markedly seasonal, showing its maximum the only geochronological and paleoclimatological in the autumn. The natural vegetation in the south data produced on speleothems from this cave are of the island is dominated by semi-arid shrubberies those supplied by Hodge (2004), who studied three and scarce forests that grow on thin calcareous soils. stalagmites whose chronology ranges from Middle In general terms the present-day bioclimatic context Pleistocene to Holocene. favors the processes that generate speleothems, a Regarding non-carbonate crystallizations, besides situation that is extensive to the whole Mediterranean the scarce gypsum cave flowers reported in the cave area. Furthermore, due to its position in the middle (Merino, 2007b), detailed observations on cave rims of the Western Mediterranean basin, Mallorca was shed light on a variety of unexpected minerals related not severely affected by the glacial periods during the to this particular morphological feature; strontianite, Pleistocene (Ginés et al., 2012a), when the climate celestine, barite, and nordstrandite were identified conditions were mostly mild but with important (Merino et al., 2009), in a morphogenetic setting that variation in precipitations. Although Th/U datings of points towards the actuation of hypogenic processes stalagmites or flowstones from Mallorca are scarce (Klimchouk, 2007). (Hodge, 2004; Ginés et al., 2011), the deposition of Classifications of speleothems have been usually speleothems during the cooler Pleistocene events established on the basis of its morphology and/or is clearly documented by the presence of abundant the genetic mechanisms involved (Sweeting, 1973; speleothems, formed during low-stand sea levels, that White, 1976; Gillieson, 1996; Hill & Forti, 1997; Ford are nowadays submerged in the present-day brackish & Williams, 2007; Palmer, 2007). So, it is a common pools of coastal caves like Cova des Pas de Vallgornera. practice to systematize these deposits according to Apart from climate dependent controls, the formation the characteristics of the water-flow that precipitates of speleothems is also conditioned by the lithologic them; in this respect, speleothems formed by dripping and textural characteristics of the rocks where the waters, flowing waters and capillary or seepage cave is located. Regarding their hydrogeological waters are distinguished together with subaqueous behavior, the Upper Miocene reefal carbonates that crystallizations. All these categories are very well- form the southern part of the island (Fornós et al., represented in this exceptional cave by means of 2002) are an example of eogenetic karst, as defined by a great diversity of speleothem types, but their Vacher & Mylroie (2002). The diagenetically immature enumeration or even description is not the goal of limestone rocks, hosting the coastal karst areas of this paper. In a more interpretative way, we will focus southern Mallorca, are characterized in general by on the localization pattern of speleothems within the high porosity and permeability values that certainly cave and on the factors that explain how they are have some influences on the speleothem formation distributed. processes. Commonly, all kinds of speleothems are present Another important factor, in this case intrinsic to throughout the cave, but not in a rambling way. The the cave, is the great development attained by Cova lithologic and textural characteristics of the rock des Pas de Vallgornera, with over 74 km of known where