Carbonates Evaporites (2011) 26:29–40 DOI 10.1007/s13146-011-0052-7

ORIGINAL ARTICLE

Geological methods applied to speleogenetical research in vertical : the example of Torca Teyera shaft (Picos de Europa, northern Spain)

Daniel Ballesteros • Montserrat Jime´nez-Sa´nchez • Joaquı´n Garcı´a-Sansegundo • Santiago Giralt

Accepted: 19 February 2011 / Published online: 5 March 2011 Ó Springer-Verlag 2011

Abstract Research in large vertical caves (shafts) is rare Introduction and usually restricted to speleological explorations because of difficult access. The systemic methodology of work in Research in vertical caves or shafts is typically limited due shafts has not been established. Picos de Europa massif, in to difficult access and methodological constraints. Scien- the Cantabrian Mountains of Spain, has a spectacular tific studies of these require speleological exploration, development of shafts deeper than 500 m. One of them is which can often include the discovery of new caves and Torca Teyera , which is 738 m deep and 4 km long. passages, as well as careful documentation (Kambesis The present study established a methodology to charac- 2007) such as cave surveys, exploration reports, photo- terize the geological and geomorphological aspects of this graphs and morphological descriptions of the cavities. special group of caves and to identify the factors contrib- The exploration of large shafts in Europe began in the uting to development. The research is multidisci- late 1970s with the publication of several speleological plinary, needs data from the cave and the caves’ studies on the Alps, Slovenia, the Pyrenees and the Picos surroundings and involves (1) the speleological cave sur- de Europa Mountains. Since 1981, the Oxford University vey at a 1:500 scale: the construction of a 3D model and Cave Club has explored the shaft Pozu del H.itu (1,135 m morphometric analyses; (2) the geomorphological mapping deep; Singleton and Naylor 1981). The calcareous massif on the cave survey at 1:500; (3) the geological and fracture of the Picos de Europa is considered as one of the prime mapping of the cave environment and cross section at sites for investigation by speleologists owing to the spec- 1:5.000; and (4) the comparison in stereographic projection tacular development of large shafts (e.g., Ogando 2007). of the obtained survey data and joint measures. The speleological documentation in Picos de Europa is extensive, but it is neither systematized nor inventoried. Keywords Karst Á Shafts Á Á The main karst systems are well known through speleo- Picos de Europa Á Geomorphological maps Á logical publications, which sometimes include geological Structural control observations (e.g., Erheyden et al. 2008). Some geological research in large caves of this massif has been developed from speleological explorations (e.g., Laverty and Senior 1981; Senior 1987). Currently, Picos de Europa contains 13% of the shafts known in the world to be deeper than 1,000 m. Most of the karst systems have shafts of only a & D. Ballesteros ( ) Á M. Jime´nez-Sa´nchez Á few kilometers. The deepest shaft in this system is Torca J. Garcı´a-Sansegundo Departamento de Geologı´a, Universidad de Oviedo, del Cerro del Cuevo´n, which is 1,589 m (Este´vez 1998), C/Arias de Velasco s/n, 33005 Oviedo, Spain and the largest cave system is the Red del Toneyu, with a e-mail: [email protected] development of 18,970 m (Gea 1991). Nevertheless, few works have focused on endokarsts (Hoyos Go´mez 1979; S. Giralt Instituto de las Ciencias de la Tierra Jaume Almera (CSIC), Smart 1984, 1986; Hoyos Go´mez and Herrero, 1989; C/Lluı´s Sole´ i Sabarı´s s/n, 08028 Barcelona, Spain Ferna´ndez- Gibert et al. 1992, 1994, 2000). 123 30 Carbonates Evaporites (2011) 26:29–40

The present study documents a methodological and leading to the formation of the main relief approach useful for the geological and geomorphological (Alonso et al. 1996; Pulgar et al. 1999; Gallastegui characterization of these special environments and dis- Sua´rez 2000). cusses the conditioning of karst development. Picos de Europa is characterized by a rough and cal- careous relief with peaks exceeding 2,500 m above sea level (asl) and by the presence of narrow canyons, such as Setting the Cares Gorge. Canyons up to 2,000-m deep evidence the important fluvial incision derived from uplifting. The karst Torca Teyera is a large shaft, 738 m deep, located on forms dominate the landscape (Hoyos Go´mez 1979; Smart the northern part of the Picos de Europa (Fig. 1), a 1984, 1986; Hoyos Go´mez and Herrero 1989; Santos mountain massif located in the Cantabrian Mountains of Alonso and Marquı´nez Garcı´a, 2005), although glacial and northern Spain. From the structural standpoint, Picos de periglacial features are preserved (Alonso 1991; Gonza´lez Europa belongs to the Cantabrian Zone of the Variscides Sua´rez and Alonso 1994; Gale and Hoare 1997; Alonso domain (Lotze 1945; Julivert et al. 1972; Alonso et al. 1998; Jime´nez-Sa´nchez and Farias Arquer 2002; Gonza´lez 2009). The bedrock consists mainly of 1,200 m of car- Trueba 2006, 2007; Moreno et al. 2009; Serrano Can˜adas boniferous limestone affected by E–W to NW–SE and and Gonza´lez Trueba 2004). Moreover, nival, gravity and south-directed imbricate variscan system thrust (Fig. 2). fluviotorrential processes also control the geomorphologi- The de´collement level of the structures is above silici- cal evolution of the landscape. clastic rocks from the Pisuerga-Carrio´n province (Pe´rez- Torca Teyera shaft was discovered, explored and sur- Estau´n et al. 1988; Marquı´nez 1989; Farias and Heredia veyed by the Groupe Spe´le´o du Doubs, the Socie´te´ Suisse 1994; Bahamonde et al. 2007; Merino-Tome´ et al. 2009). de Spe´le´o-Section de Gene`ve, the Socie´te´ des Amateurs des During the Alpine orogeny, some of these thrusts were Caverns and the Spe´le´o Club of Nyon between 1979 reactivated, causing the rotation of some thrust sheets and 1982 (Borreguero 1986). During these explorations,

Fig. 1 Situation map of the Picos de Europa massif. The locations of the cave of study (Torca Teyera, Fig. 5) are also shown

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Fig. 2 Geological map of Picos de Europa (after Martı´nez Garcı´a and Rodrı´guez Ferna´ndez 1984; Marquı´nez 1989; Merino-Tome´ et al. 2009). Location of Torca Teyera (Fig. 5) is shown

Borreguero (1986) prepared the first karst research pre- discovered by the Asociacio´n Deportiva GEMA. At the senting the structural control and cave development. From present, Torca Teyera has 4 km of known passages 2007 to 2009, 2,700 m of new cave passages were reaching a depth of 738 m.

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Methodology Sa´nchez et al. 2006; Ford and Williams 2007). Sometimes, the geomorphological mapping and the survey were per- The present methodology includes multidisciplinary formed simultaneously. The limits of the different features observations to obtain both surficial data and data from the were established and projected on the survey map. Some of underground of the cave. The method is adapted to attain the geomorphological elements located in the cave walls access to the shaft, which is difficult, and is based on spe- could not be represented by projecting them on the survey, leological (Butcher 1950), geomorphological and structural since the survey had to be made at different heights above geology techniques (Alonso et al. 1999; Jime´nez-Sa´nchez the ground. This problem was due to the difficulties in et al. 2004, 2005, 2006). The method includes the defini- establishing objectively the boundary between the floor and tion of an area of 12 km 2 (Figs. 1, 2) including the cave the wall of the cave. Therefore, the geomorphological and its surroundings: (1) the speleological survey at a 1:500 elements are shown schematically on the outside contour of scale; (2) the geomorphological mapping of the cave at a the passages to minimize these problems. These elements scale of 1:500 and surrounding of the cavity at a 1:5,000 were brought down on the walls along an axis located on scale; and (3) the structural study that includes the geo- the edge of the passages. logical and fracture mapping at a 1:5,000 scale, the cross A geomorphologic mapping of the cave surroundings section, rose diagram analyses and the definition of the was charted at a 1,500 scale using field observations and joints families on stereographic projection. photo interpretation. This map covers a surface of 12 km2 and includes different landscape features that are classified Cave survey and morphometric analyses according to genetic criteria (Martı´n-Serrano et al. 2004)in karstic, glacial, snow, periglacial, gravity and mixed forms. The cave survey that corresponds to the Torca Teyera shaft This map also includes the entrances of the caves and the is the cave projection in a horizontal plane. The survey was projection of their passages that have been explored by the mapped using the speleological classical method at a 1:500 speleologists (Borreguero 1986; Carbajal Rodrı´guez and scale where successive stations were defined in the pas- Saiz Barreda 2003); Carbajal et al. 2008; Ballesteros et al. sages. Distances, orientation and dip data were measured 2009, 2010). between stations using a tape measure or laser, a ruler and a clinometer, respectively. The cavity survey was made by Geological mapping and structural analyses considering a reference level between 30 cm and 1.5 m above the cave floor. The collected data were managed The geological and fracture maps, covering a combined using the VisualTopo.503 software program (David 2009) total surface of 12 km2 (Fig. 2), were produced at a to define the survey line (a line connecting the stations). 1:5,000 scale by means of field work and photo inter- The survey is conducted over the survey line consulting the pretation. Three geological cross sections were also pre- sketches made during the data collection phase. The pared. The cavity study and others were projected over VisualTopo.503 software produces a 3D model approxi- the maps and over the geological cross sections. Rose mating the passages by an octagonal conduit, the axes of diagram from the data of the fracture map was prepared to which are the height and width of the passages. compare with a rose diagram obtained from the orienta- The morphometric analyses consist of the representation tion of the cave passages. Furthermore, 157 joint data of the survey data on stereographic projection, a common measures (dip and direction) were taken on the surface structural technique applied to compile figures on the (124) and in the shaft (33). These data were represented direction and dip of the cave passages. The orientation and on stereographic projection and a density analysis was inclination data are represented on the plot per meter of made. The analysis of densities allows the establishment surveyed cave. Afterward, a density analysis is made and of joint families in which the median plane is illustrated the main groups of passages established according to this in the plot with the bedding. Afterward, the density plot of direction and dip. the orientation and dip of the passages were represented on the stereographic projection to compare the control of Geomorphological research the joints and the bedding with the direction and incli- nation of the passages. The geomorphological research includes geomorphological mapping of both cave and cavity surroundings. Cave geo- morphological mapping was carried out at a 1:500 scale, Results and discussion taking the cave survey as a topographical basis. Cavity features were inventoried and classified according to The application of the methods described above obtained genetic, morphological and sedimentary criteria (Jime´nez- the following results. 123 Carbonates Evaporites (2011) 26:29–40 33

Cave survey and morphometric analyses cave passages is also shown. The group of geomorpho- logical features includes (1) , (2) fluviokarst The cave survey and the 3D model are shown in Fig. 3. and (3) gravity forms. Speleothems are classified into The cavity consists of three levels of galleries (horizontal dripstones, flowstones, and mixed and other forms. Drip- passages) and several pits (vertical passages). The galleries stone forms include , and columns. represent 72% of the development of the cave and are The flowstones present as cascades and laminar forms. The narrow meanders up to 50 m that join as tributaries and mixed forms include masses that originated by converge to the NE. Thus, the cavity is a branchwork cave drip and flow of water (Fig. 4a). Other peculiar forms such defined by Palmer (1991). The passages follow the NW–SE as pool deposits or collaroids forms are noted. The fluvi- and NE–SW direction in the northern part of the cavity and okarst forms are classified as erosive forms or sedimenta- the N–S and E–O trend in the southern area. tion forms. The erosive forms include scallops, roof The groups of passages according to their orientation pendants, corrosion notches, solution runnels, potholes and and dip were determinate by the representation of the relict channels. The erosive forms are mostly located in survey data on stereographic projection. This approxima- active and canyon shaped passages, shafts and at higher tion is sufficient for passages, but not fully adequate for levels, such as relict forms (Fig. 4b). The fluvial deposits shafts because the survey depends on the track of the are divided into deposits of the active stream channel and speleologists. Therefore, a part of the subvertical measures the fluvial terrace (Fig. 4c). These deposits have been does not represent subvertical passages. This fact has been classified according to the grain size as pebbles, sand and taken into account for the interpretation of data. Four pebbles, sand, and clay and mud. Finally, the gravity forms groups of passages were established and the median value are debris deposits, fallen boulders and single pebbles and of the direction and dip are: (1) subvertical, (2) N10°W/ gravel that have been shed by rockfall processes (Varnes 20°NW, (3) N45°E/20°NE and (4) N125°E/0°. 1978). The breakdown deposits cover or are covered by other fluvial and precipitation deposits. The geomorpho- Cave geomorphological mapping logical map also includes other remarkable geological aspects: quartz, galena and malachite mineralizations, A selected portion of the geomorphological map of the altered substrate, structural data and volcanic rocks. southern sector of the shaft is illustrated in Fig. 4. The legend of the map is divided into three parts: issues related Geomorphological mapping of the cave surrounding to (1) the survey, (2) geomorphological features and (3) geological aspects. The first group includes morphometric Torca Teyera is located under a free and half-exposed data related to the passages: contour (using the upper and karren, dominated by karstic, glacial and nival activity. The lower contour when there is an overlap), scarps and pits, geomorphologic map of the cave surroundings is shown in presence of rivers or lakes, the slope of the ground and the Fig. 5a. The distribution of the geomorphological features value of altitude and depth from the cave entrance at is uneven. The deposits represent 27.3% of the area of several points. The position of possible continuations of study and are mainly situated in the valleys. The erosive

Fig. 3 a The cave survey and b the 3D model of Torca Teyera. The study location described in Fig. 4 is shown

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Fig. 4 Details from a selected portion of the cave geomorphology map, its legend and pictures of different passages. Inset a represents a gallery shaped like a canyon, b a stalagmite mass and c terrace deposits formed by levels of mud and sand

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Fig. 5 a Geomorphological map, b geological map and c fracture map of Torca Teyera area. The shaft is projected on maps and cross section of Fig. 6a. The data of the caves are from Borreguero (1986), Carbajal Rodrı´guez and Saiz Barreda (2003), Carbajal et al. (2008), Ballesteros et al. (2009, 2010)

forms have been identified at the hillside and the peaks. without slope and are mainly formed by mud that comes The closed depressions occupy 5.0% and are developed on from the dissolution of the limestone. The are slopes up to 40°. depressions of 5- to 20-m wide and 1- to 5-m depth and Karstic, snow, glacial, periglacial and gravity forms associated with gravitational deposits. The dolines are were mapped. The former includes karstic deposits, closed and dominated by breakdown processes; thus, they dolines, glaciokarst depressions, caves and cave passages are mostly collapsed sinkholes. The glaciokarst depressions projections. The karst deposits are situated in the areas are closed hollows of 600-m wide and 70-m depth located

123 36 Carbonates Evaporites (2011) 26:29–40 at the valley bottom. The depressions originated from breccias and boundstone with botryoidal cement fans. The glacial, karstical and snow activity (Smart 1986; Alonso platform top facies include stratification rocks, mainly 1998). The entrances of caves are mainly situated in formed by skeletal pack, to grainstone limestone and pink sinkholes or glaciokarst depression and represent cave fossil-rich limestone. Moreover, an andesitic dyke is rec- passages truncated by erosion. Torca Teyera is located ognized in the western middle part of the geological map. under a free karren with a lot of closed depressions, gravity The cavity studied is developed on limestone affected by deposits and some glacier cirques. an NW–SE trending, subvertical and SW-directed thrusts The nivation forms include one moraine and some cir- and other faults, the direction of which is SE–NW, SW–NE ques originated by snow activity. The nivation cirques are or N–S (Figs. 5b, 6a). Two sequences of thrusts have been observed in some walls of dolines and in scarps oriented to recognized based on their geometric relationships. The first the NE or SW. The snow moraine is located under one sequence dips 50–70 NE and is interrupted by an out-of- nival cirque. Glacial forms cover till deposits, horns, areˆte, sequence anomaly, which dips by 80–90° NE. cirques and moraines. A glacial valley is observed in the Figure 5a shows 2,367 fractures in the study area; these NW of Torca Teyera shaft. Till deposits, mainly formed by are represented in a rose diagram (Fig. 6b). The plot shows limestone pebbles and boulders, sand and mud, are found three groups of fractures with directions: (1) NE–SW, (2) in this valley. In some cases, boulders of limestone in N–S and (3) NW–SE. The first group represents 45% of the certain facies are found on the bedrock of limestone with total fractures and the second group represents another 17%. other facies. The till is often presented in moraines of 1- to The direction of the cave passages are analyzed by another 6-m wide and 50- to 60-m long. The horns are degraded rose diagram (Fig. 6c). On comparing both (fracture and and are situated in the peaks where some areˆtes converge. cave direction) rose diagrams, the first structural control of The cirques are greatly degraded by karstification and their the orientation can be semiqualitatively established. The size is between 100 and 300 m. The only periglacial evi- dispersion of values of the shaft orientation is greater than dence is a rock glacier shown on the eastern part of the the fracture data, although the NW–SE direction of the cave map. The deposit is formed by limestone gravels and is noted. The group considered as Fracture 1 is the most boulders, and presents some transverse and longitudinal abundant collection, but its influence on the cavity devel- ridges and furrows. opment is less than the group considered as Fracture 2. This Gravitational forms include debris fall, talus deposits method does not consider the influence of the bedding and and rock avalanches and are situated under scarps and in the intersection between discontinuities; consequently, it is sinkholes. The debris fall generally consists of angular only a first approximation to the structural factor. pebbles and gravels of limestone. The talus deposits are Seven families of joints have been established on the mostly formed of limestone pebbles and gravel, sand and stereographic projection. The average plane of each family mud; these are usually vegetated. The rock avalanches are is represented in Fig. 7a. The families J2, J3 and J5 cor- formed from disorganization of angular boulders and respond to the fractures already recognized in a previous pebbles of limestone in the NE of the map. work (Borreguero 1986). The density plot of the orientation Some geomorphological features (till, closed depres- and dip of the passages has been shown in gray scale on the sions, cirques, areˆtes, gravity deposits and the rock glacier) stereographic projection (Fig. 7a) to compare the main are mainly orientated following the NW–SE and NE–SW orientations and dips of the joints, the bedding and the cave directions. This trend represents the orientation of the passages. Figure 7a highlights that subvertical cave pas- bedding, thrusts and the main faults. sages (Group 1 of galleries) are conditioned by the joint families J1, J3, J4 and J6, as well as their intersections. The Geologic mapping and structural research galleries belonging to Group 2 (N10°W/20°N) are mainly controlled by the intersection between the families J5 and The cavity surrounding of the geological map was formed J6. The passages dipping down 20° to the NE (Group 3) by both the cave development and the tectonics (Fig. 5b). are ruled by the intersection between family J1, J2, J5 and The surroundings of Torca Teyera were formed by 1,000 m J7. The latter group of passages consists of horizontal of limestone of the Valdeteja and Picos de Europa For- galleries in the direction N125°E and follows the bedding mations stacked vertically. The limestone is divided into (Fig. 7b). three strata domain as defined by Bahamonde et al. (2007): (1) toe of slope and basin facies, (2) slopes facies and (3) platform top facies. The toe of slope and basin facies Conclusions include well-stratified coarse-grained beds formed by breccias, bioclastic pack to grainstone limestone, chert and The use of a multidisciplinary methodology including the shales. The slopes facies consist of massive limestone, speleological cave survey, geomorphological mapping and 123 Carbonates Evaporites (2011) 26:29–40 37

Fig. 6 a One of the three cross sections prepared, the position of which is shown in Fig. 5b. b Rose diagram of the fracture direction and c of the orientation of Torca Teyera passages

structural techniques is adequate to develop reliable geo- galleries display a canyon morphology, modeling results are morphological assumptions for a cave with difficult access. not accurate because, in the model, the value of passage Also, this multidisciplinary methodology allows the defi- widths decreases with the distance to the floor and the roof. nition of factors controlling karst development, especially After modeling, further analyzing the cave survey data with the quantitative evaluation of the structural influence on stereographic projection is useful to quantitatively classify endokarst. the cavity passage according to the direction and dip. The speleological cave survey is a graphical document Cave geomorphologic mapping indicates the different that is useful to plot geological and geomorphological forms and their spatial distribution. The map informs about information. However, its development is complex due to the genetic processes and their spatial and temporal rela- the adversity of the environment and the subjective criteria tionships. These aspects are the base of the speleogenetical of the researcher who has to include different elements model of the shaft. Some limitations of the method are located at inconstant heights above the floor. The 3D model conditioned by the precision of the cave survey. In the wall approximates the geometry of the endokarst system as a of the passages, several interesting forms are present; whole. In the scale of the passage, the approximation is not nevertheless, these forms cannot be represented on the cave correct because the irregularities of the passage walls are survey because the plot is only a horizontal projection. If not seen. When a section of a gallery or a shaft is not the forms on the walls are projected over the survey, all of subcircular, the model does not properly represent the shape them are situated in the same place. The imprecision of of the passage because the software uses an octagonal information on walls can be solved by projecting down the section to approximate the shape of the section. Where the forms on the cave limits.

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Fig. 7 a Stereographic projection of the orientation and dip of the passages showing the position of the planes that represent the main families of joints and the bedding; b a cave passage that has been controlled by the bending; and c the structural control of each group of galleries

The geological and fracture mapping of the cave sur- Alonso V (1998) Covadonga National Park (Western Massif of Picos rounding and the cross section with the shaft projection de Europa, NW Spain): a calcareous deglaciated area. Trabajos de Geologı´a., vol 20. Universidad de Oviedo, pp 167–181. http:// determine the qualitative structural control of the cave. The www.geol.uniovi.es/TDG/Volumen20/TG20-06.PDF (Febraury) comparison between the fracture direction and the orien- 2009 tation of the cavity passage allows a first hypothesis about Alonso JL, Pulgar JA, Garcı´a-Ramos JC, Barba P (1996) Tertiary the structural control. This comparison does not consider basins and Alpine tectonics in the Cantabrian Mountain (NW Spain). In: Friend P, Dabrio C (eds) Tertiary basins of Spain. the bending, dip or the hypothetical intersection between Cambridge University Press, Cambridge, pp 19–22 the discontinuities. These limitations can be resolved using Alonso JL, Garcı´a-Ramos JC, Gutie´rrez-Claverol M (1999) Control stereographic projection, where the dip and the direction of estructural de la cavidad ka´rstica ‘‘La Cuevona’’ (Ribadesella, joints, bedding and cave passages are represented. This plot Asturias). In: Andreo B, Carrasco F, Duran JJ (eds) Contribucio´n del estudio cientı´fico de las cavidades ka´rsticas al conocimiento that includes survey data together with structural data geolo´gico. Patronato de la Cueva de Nerja, Nerja, pp 65–76 evaluates quantitatively the relationship between the Alonso JL, Marcos A, Sua´rez A (2009) Paleogeographic inversion structure and the endokarst. resulting from large out of sequence breaching thrusts: The Leo´n Fault (Cantabrian Zone, NW Iberia). A new picture of the Acknowledgments This research has been funded through the external Variscan Thrust Belt in the Ibero-Armorican Arc. CONTRACT project (CN-06-177) provided by ASTURIAS Geologica Acta 7(4):451–473 GOVERNMENT-OVIEDO UNIVERSITY, CALIBRE project Bahamonde JR, Merino-Tome´ OA, Heredia N (2007) A Pennsylva- (CAVECAL) (CGL2006-13327-C04/CLI) provided by Ministerio de nian microbial boundstone-dominated carbonate shelf in a distal Educacio´n y Cultura and GRACCIE project (CONSOLIDER foreland margin (Picos de Europa Province, NW Spain). PROGRAM) (CSD2007-00067) provided by Centro de Investigacio´n Sediment. Geology 198:167–193 Cientı´fica y Tecnolo´gica. We acknowledge Dr. Juan Bahamonde, Ballesteros D, Calduen˜o Garcı´a MA, Can˜o´n Salgado G, Estrada Dr. O´ scar Merino, Gemma Sendra, Irene de Felipe, Asociacio´n Gonza´lez S, de Felipe Pitcairn J, Ferna´ndez Gonza´lez R, Deportiva Gema, Grupo Espeleolo´gico Polifemo and GES Mont- Ferna´ndez Valencia R, Martı´nez Mun˜iz R, Puerta Elorza EA an˜eiros Celtas for their help. (2009) Semun˜o´n 2009, Exploracio´n espeleolo´gica en Pen˜a Jascal, Picos de Europa, NO de Espan˜a. Oviedo, Spian. Unpublished, 41p Ballesteros D, Puerta Elorza EA, Ferna´ndez Valencia R, de Felipe References Pitcairn J (2010) Torca Teyera. Subterra´nea. Federacio´n Espan˜- ola de Espeleologı´a 30:24–26 Alonso V (1991) Geomorfologı´a de las cabeceras de los rı´os Narcea, Borreguero M (1986) Special Picos: Puertos de Ondo´n. Neuchaˆtel, Navia y Sil y del Parque Nacional de la Montan˜a de Covadonga Suisse. Unpublished, 118 p (NO de la Penı´nsula Ibe´rica). Ph D thesis. Universidad de Butcher AL (1950) Cave survey. Publication of the Cave Resarch Oviedo. Oviedo. Spain group of Great Britain 3, 40 p

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