Italian Institute of Speleology

Bologna, Italy

Italian Institute of Speleology

Bologna, Italy
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Du Preez G.C.,North West University South Africa | Forti P.,Italian Institute of Speleology | Jacobs G.,North West University South Africa | Jordaan A.,North West University South Africa | Tiedt L.R.,North West University South Africa
International Journal of Speleology | Year: 2015

Ngamiland in northwestern Botswana hosts the Gcwihaba Caves which present unique subterranean environments and host speleothems never before recorded. Cave atmospheric conditions can be extreme with temperatures as high as 28°C and relative humidity nearing 99.9%. Within Dimapo and Diviner’s Caves peculiar root speleothems that we named ‘Hairy Stalagmites’ were found. These stalagmites are closely associated with the roots of Namaqua fig (Ficus cordata) trees that enter the cave environment in search of water. Pieces of broken stalagmites were sampled from Dimapo Cave for further investigations. Stereo and electron microscopy revealed that the Hairy Stalagmites consist of multiple intertwined tubes created when thin films of CaCO3are deposited around fine lateral roots. The importance of the roots is substantiated with evidence of calcified epidermal cells, apical meristems and epidermal imprints. The development of these stalagmites starts when roots accumulate on the cave floor in the vicinity of a water drip and a root nest is created to capture the water. From this point the roots grow upwards (positive hydrotropism) allowing the development of the calcite structure, and as CO2diffusion and evaporation occurs, CaCO3is deposited. The environmental conditions necessary for the growth of Hairy Stalagmites, as well their developmental mechanism, are discussed and illustrated. © 2015, Societa Speleologica Italiana. All rights reserved.

Gazquez F.,University of Almeria | Calaforra J.-M.,University of Almeria | Rull F.,University of Valladolid | Forti P.,Italian Institute of Speleology | Garcia-Casco A.,University of Granada
International Journal of Speleology | Year: 2012

Unusual amberine-coloured speleothems were recently found in El Soplao Cave (Cantabria, Spain). Chromophore elements such as Fe, Mn, Cd, Co or Ti were not present in significant quantities. Rather, our data show that their colour comes from leachates of fossilized organic material hosted in the carbonaceous Urgonian facies of the host rock. These leachates are related to the Cretaceous amber deposit that has been recently discovered in the vicinity of El Soplao Cave. The presence of humic and fulvic acids of fossil origin were confirmed by IR and Raman spectroscopic analysis of the carbonaceous strata and the speleothems. In addition, the mineralogy of the amberine speleothems was studied. Alternating bands made of calcite and aragonite reveal that periods of humidity and aridity occurred within the cave during the speleothem genesis.

Gazquez F.,University of Almeria | Calaforra J.-M.,University of Almeria | Forti P.,Italian Institute of Speleology | Rull F.,University of Valladolid | And 3 more authors.
International Journal of Speleology | Year: 2012

Some of the most outstanding hypogenic gypsum speleothems worldwide have been recently discovered in the Naica mines. The Cueva de las Espadas (Swords Cave), which lies at 120 m depth, hosts a rare type of speleothem called "espada" ("sword"). This study contributes to the understanding of the mineralogical composition of these singular speleothems, by means of their examination using micro-Raman spectroscopy, FT-IR spectroscopy and EDX microprobe. Our data revealed a complex mineralogy comprising a high-purity selenite core covered by several layers of calcite, aragonite and gypsum. Solid inclusions of polymetallic oxides (Mn-Pb-Zn) and graphite were also detected. The position of the water table during the genesis of the "espada" speleothems (over the past 60 kyr) was deduced from their mineralogy. Water level fluctuations at around -120 m depth led to environmental changes within the Cueva de las Espadas. The selenite core and gypsum layers were precipitated under biphasic (water-rock) conditions when the cave was submerged under hydrothermal water. The aragonite precipitation required triphasic (air-water-rock) conditions and occurred when the water table intercepted the cave, allowing the CO2 exchange necessary for carbonate precipitation. Solid inclusions were trapped in an aerobic environment when the gypsum-aragonite boundary condition occurred. A thin calcite layer was precipitated under vadose conditions after the water table definitively moved out of the cave.

A detailed petrographic, structural and morphometric investigation of different types of caves carved in the quartz-sandstones of the "tepui" table mountains in Venezuela has allowed identification of the main speleogenetic factors guiding cave pattern development and the formation of particular features commonly found in these caves, such as funnel-shaped pillars, pendants and floor bumps. Samples of fresh and weathered quartz-sandstone of the Mataui Formation (Roraima Supergroup) were characterised through WDS dispersive X-ray chemical analyses, picnometer measurements, EDAX analyses, SEM and thin-section microscopy. In all the caves two compositionally different strata were identified: almost pure quartz-sandstones, with content of silica over 95% and high primary porosity (around 4%), and phyllosilicate-rich quartz-sandstone, with contents of aluminium over 10% and low primary porosity (lower than 0.5%). Phyllosilicates are mainly pyrophyllite and kaolinite. SEM images on weathered samples showed clear evidence of dissolution on quartz grains to different degrees of development, depending on the alteration state of the samples. Grain boundary dissolution increases the rock porosity and gradually releases the quartz grains, suggesting that arenisation is a widespread and effective weathering process in these caves. The primary porosity and the degree of fracturing of the quartz-sandstone beds are the main factors controlling the intensity and distribution of the arenisation process. Weathering along iron hydroxide or silt layers, which represent inception horizons, or a strata-bounded fracture network, predisposes the formation of horizontal caves in specific stratigraphic positions. The loose sands produced by arenisation are removed by piping processes, gradually creating anastomosing open-fracture systems and forming braided mazes, geometric networks or main conduit patterns, depending on the local lithological and structural guidance on the weathering process. This study demonstrates that all the typical morphologies documented in these quartz-sandstone caves can be explained as a result of arenisation, which is guided by layers with particular petrographic characteristics (primary porosity, content of phyllosilicates and iron hydroxides), and different degrees of fracturing (strata-bounded fractures or continuous dilational joints). © 2014 Elsevier B.V.

Ruggieri R.,Centro Ibleo Of Ricerche Speleo Idrogeologiche | Ruggieri R.,University of Nova Gorica | De Waele J.,Italian Institute of Speleology
Acta Carsologica | Year: 2014

The peninsula of San Vito Lo Capo, 50 km West of Palermo (Sicily), is characterised by the presence of a wide set of evidences of past sea level changes, such as marine terraces, notches, marine and coastal caves with phreatic overgrowths on speleothems, and continental and marine deposits. The exceptional good preservation of these landforms and deposits has been used by different authors for the reconstruction of sea level changes and neotectonic movements. Among the many caves discussed by previous authors, most are of marine origin and can preserve signs of old sea level highstands such as notches and marine or continental sediments. However, two caves in particular, Fantasma Cave and Falesia Rocca Rumena I cave, show evidences to be flank margin caves. Both caves are records of rising and falling sea level, and their position and the correlation with marine terraces suggest them to be around 0.8 and 1.1-1.2 Ma old respectively. This study shows that not all sea level high stands are preserved in the stratigraphical and geomorphological record.

De Waele J.,Italian Institute of Speleology | Lauritzen S.-E.,University of Bergen | Parise M.,National Research Council Italy
Earth Surface Processes and Landforms | Year: 2011

A large number of uniform cone-shaped dissolution pipes has been observed and studied in Quaternary coastal calcareous arenites in Apulia and Sardinia (Italy) and Tunisia. These cylindrical tubes have a mean diameter of 52·8cm and are up to 970cm deep (mean depth for sediment-free pipes is 1·38m). They generally have smooth walls along their length, are perfectly vertical and taper out towards their bottoms. Their development is not influenced by bedding nor fractures. Sometimes their walls are coated by a calcrete crust. Their morphology has been studied in detail and their relationships with the surrounding rocks and with the environment have been analysed. The perfectly vertical development is a clear evidence of their genesis controlled by gravity. The depth of the dissolution pipes can be described by an exponential distribution law (the Milanovic distribution), strongly suggesting they developed by a diffusion mechanism from the surface vertically downward. We believe dissolution pipes preferentially form in a covered karst setting. Local patches of soil and vegetation cause infiltration water to be enriched in carbon dioxide enhancing dissolution of carbonate cement and local small-scale subsidence. This process causes the formation of a depression cone that guides infiltrating waters towards these spots giving rise to the downward growth of gravity-controlled dissolution pipes. A change of climate from wetter phases to drier and hotter ones causes the formation of a calcrete lining, fossilizing the pipes. When the pipes become exposed to surface agents by erosion of the sediment cover or are laterally breached the loose quartz sand filling them may be transported elsewhere. © 2010 John Wiley & Sons, Ltd.

Galli E.,University of Modena and Reggio Emilia | Brigatti M.F.,University of Modena and Reggio Emilia | Malferrari D.,University of Modena and Reggio Emilia | Sauro F.,Italian Institute of Speleology | De Waele J.,Italian Institute of Speleology
American Mineralogist | Year: 2013

Rossiantonite, ideally Al3(PO4)(SO4) 2(OH)2(H2O)10·4H 2O, triclinic (space group P1̄), a = 10.3410(5), b = 10.9600(5), c = 11.1446(5) Å, α = 86.985(2), β = 65.727(2), γ = 75.064(2)°, V = 1110.5(1) Å3, Z = 2, is a new mineral from the Akopan-Dal Cin cave system in the Chimanta massif (Guyana Shield, Venezuela). The mineral occurs as small (≤0.15 mm) and transparent crystals in a white to slightly pink fine-grained sand, filling spaces between boulders of weathered quartz sandstone. Associated phases are gypsum, sanjuanite, rare alunite, quartz and micro-spherules of amorphous silica. Rossiantonite is colorless with a white streak and vitreous luster. The mineral is brittle with irregular to sub-conchoidal fracture and it shows a poorly developed cleavage. Rossiantonite is biaxial and not pleochroic, with mean refractive index of 1.504. The calculated density is 1.958 g/cm3. Electron microprobe analyses, with H2O measured by thermogravimetric analysis, provided the following empirical formula based on 28 O apfu: Al2.96Fe 0.03P1.01S2H30.02O 28. The five strongest lines in the X-ray powder diffraction pattern, expressed as d (Å), I, (hkl) are: 4.647, 100, (210); 9.12, 56, (100); 4.006, 53, (220); 8.02, 40, (110); 7.12, 33, (011). The crystal structure, refined using 3550 unique reflections to R = 0.0292, is built of PO4 and Al O6 polyhedral rings, creating complex chains parallel b by sharing the OH-OH edge belonging to the Al(3) polyhedron. Three symmetrically independent Al sites can be identified, namely: Al(1), Al(2), and Al(3). Tetrahedral sites, occupied by P, share all their apexes with AlO6 octahedra. Unshared octahedral apexes are occupied by water molecules. Four additional water molecules are placed in between the previously identified chains. Two oxygen tetrahedra, occupied by S atoms, are connected along the chains by means of weak hydrogen bonding. The rossiantonite structure shows similarities with minerals belonging to the sanjuanite-destinezite group.

Vigna B.,Polytechnic University of Turin | Fiorucci A.,Polytechnic University of Turin | Banzato C.,Polytechnic University of Turin | Forti P.,Italian Institute of Speleology | De Waele J.,Italian Institute of Speleology
Zeitschrift fur Geomorphologie | Year: 2010

In the morning of February 15th 2005, during excavation works in an underground gypsum quarry at Moncalvo (Monferrato area. Asti, Northern Italy), a water-bearing fracture was intercepted at level 134 m a.s.l. During the night a large amount of water (approximately 60,000 m3) and mud invaded the quarry tunnels reaching a height of 139 m a.s.l. the morning of the day after. Meanwhile a large sinkhole (20 m wide and 10 m deep) formed on the surface. Hydrogeological surveys were immediately carried out to follow the quickly evolving situation, while speleological and geomorphological fieldwork was made possible only seven months later. Two important caves were discovered both showing clear evidence of a hypogenic origin with sculpted morphologies due to slowly flowing water under pressure. The sinkhole formed by the collapse of one of the main chambers of the biggest of these caves, when buoyant support provided by the water started to decrease due to lowering of the virtual water table. The recharge of this karst system is from below and only very minor quantities of infiltration water come from the above lying surface, as has also been confirmed by hydrochemical analysis. This hypogene karst is completely invisible at the surface and develops entirely underground showing no relation whatsoever with the surface. Its presence is therefore extremely difficult to reveal and such types of karst can thus make up extremely dangerous situations. This is the first example of hypogene gypsum cave related to ascending waters in Italy. © 2010 Gebrüder Borntraeger Verlagsbuchhandlung Stuttgart Germany.

Forti P.,University of Bologna | Sanna L.,Italian Institute of Speleology
Episodes | Year: 2010

The caves of Naica (Chihuahua, Mexico) are perhaps the most famous mine caves of the world due to the presence of gigantic gypsum crystals. Nevertheless, very little research has been carried out on these crystals until now. An international multidisciplinary investigation started in 2006 with the aim not only to define the genesis and the age of the Naica gypsum crystals, but also to focus other important scientific aspects of these caves and to ensure a complete documentation and knowledge of these natural wonders which will not be accessible anymore in a few couple of years. The preliminary results of this, still in progress, research allow to date the giant crystals and to define the boundary conditions and the mechanisms which induced their development. For the first time pollens have been extracted from gypsum crystals and their analyses evidenced that some 35 Ky BP the Naica climate was cooler and more humid than today.

Forti P.,Italian Institute of Speleology
Zeitschrift fur Geomorphologie | Year: 2010

The Naica caves and their large gypsum crystals were discovered almost a century ago, but only recently four new caves were unveiled, the largest of which (Cueva de los Cristales) hosts by far the largest gypsum crystals of the world. Until now studies were focused on the mechanisms allowing for the development of the giant crystals while the genesis and the evolutionary steps of the Naica caves were completely ignored. The aim of the present paper is to close this gap. The thermal fluids responsible, since 25 Myr ago, of the evolution of the Naica ore bodies were always characterized by net deposition, therefore the permeability of the hosting formation was reduced and no karst voids had the possibility to develop. 1-2 Myr ago tectonic stresses partially displaced the ore bodies giving rise to open joints and fractures closely related to three main faults, which still now control the uplift of the thermal fluids. Since then the thermal waters became aggressive with respect to carbonate formations, thus small cavities had the possibility to develop at different levels inside the aquifer. This process lasted for a relatively short time interval as testified by the clear tectonic shape maintained by all these cavities. Scarcity of corrosional features did not allow for a detailed reconstruction of the cave evolution, which was in turn achieved by a multidisciplinary analysis of the thick chemical deposits hosted inside each cave. The evolutionary steps were several and complex, related to different speleogenetic mechanisms. Although they were always controlled by the presence of the thermal aquifer, the resulting evolution was somewhat different from cave to cave, reflecting alternately deep-seated phreatic, epi-phreatic and vadose environments. From this point of view the most interesting cave is Cueva de las Espadas, the evolution of which was characterized by several changes between these three environments through time, while the deeper caves suddenly changed from deep phreatic to vadose when the mine dewatering lowered the groundwater below the -290 m-level some 20 years ago. The anthropogenic processes induced by the mine depression cone had relevant consequences on the cave development giving rise to the evolution of several new diagenetic minerals (over 35 minerals - mainly oxides-hydroxides, but also sulphates and silicates - are actually forming, some of them new for the cavern environment) but also greatly enhancing the condensation corrosion and dissolution processes which, in a few years, will be responsible not only for the damage of the giant gypsum crystals but also for their complete destruction. For this reason one of the main tasks for the scientists involved in the study of the Naica caves is to search for the best way to preserve, at least partially, this incredible underground world. © 2010 Gebrüder Borntraeger Verlagsbuchhandlung, Stuttgart, Germany.

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