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 degrees Celsius and relative humidity nearing 99.9%. Within Dimapo and Diviner's Caves peculiar root speleothems that researchers 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 CaCO3 are deposited around fine lateral roots. The importance of the roots is substantiated with evidence of calcified epidermal cells, apical meristems and epidermal imprints. From this point, the roots grow upwards (positive hydrotropism) allowing the development of the calcite structure, and as CO2 diffusion and evaporation occurs, CaCO3 is deposited.
Ojo de la Reina is the first and the smallest cave intersected at the -290 level in the Naica Mine (Mexico), therefore it was the firstcavity in which the lowering of temperature induced by mine ...ventilation caused condensation over crystals’ surface since 2005. Theconsequent dissolution of the gypsum crystals and subsequent condensed water evaporation lead to the deposition of several newminerals, among which some highly soluble Mg/Na compounds (bloedite, epsomite, halite, hexahydrite, kieserite, starkeyite). Thesingle available source of Mg and Na ions in this minerogenetic environment is represented by the huge fluid inclusions widespreadwithin the crystals. The condensation occurs mainly along the widened principal exfoliation (010) planes, and allows to an easy andfast opening of the fluid inclusions that consequently drip Mg-rich fluids stored inside them. Finally the evaporation of the relativelysmall volumes of involved water allows to the development of the high soluble Mg and Na compounds.
The origin and the evolution of giant selenite crystals in Naica caves, together withthe understanding of their growthmechanisms, is one of the aims of the international multidisciplinary research, ...called the “Naica Project”. In this context, the exact timing of when the gypsum nucleation started and whether its growthhas been constant over time, have been investigated. The preliminary data obtained withthe U–Th disequilibrium method show significant differences in ages for gypsum (between 191 ± 13 kyr for one of the Ojo de la Reina cave crystals and 57 ± 1.7 kyr for the base of Espadas cave’s spar) and have produced a coarse chronological interval of growth. The crystal depositional rates vary from 0.56 to 1.22 mm/kyr, in excellent agreement withthe laboratory tests for gypsum deposition under present conditions performed in the deepest part of the mine. These results are also consistent witha multistage precipitation started at different times in the Naica caves (first in caves at the upper level, where gypsum was subsequently dissolved, and only later in the deeper part of the aquifer under stable conditions) and allow us to improve the knowledge on the speleogenetic evolution of these caves.
Gazquez F., Calaforra J., Forti P., Rull F. and Martinez-Frias J. 2012. Gypsum-carbonate speleothems from Cueva de las Espadas (Naica mine, Mexico): mineralogy and palaeohydrogeological implications. ...International Journal of Speleology, 41(2), 211-220. Tampa, FL (USA). ISSN 0392-6672. http://dx.doi.org/10.5038/1827-806X.41.2.8 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.
The morphological knowledge of the territory, bothin its surface and subterranean aspects, is the main premise to all decision-making procedures as well as all planning and management activities. ...Knowledge takes shape into reliable precise and complete thematic cartography and databases, whichare necessary for anybody dealing withunderground contexts: speleologists, scientists, public administrations, managing authorities etc. Surveys in caves are normally carried out withtraditional techniques and instruments, whichare essential for a first representation but not enoughfor a pragmatic effective topographic approach. Laser scanning technique can be an alternative to the traditional systems. Laser scanning quickly acquires the shape of cavities as “point clouds” (x, y, z coordinates and colour values) and produces a highprecision database of the surveyed object. Laser scanning technology is therefore a feasible way to document caves in a precise exhaustive way, limiting risks relating to lack and/or inadequacy of data. The present paper explains the laser scanning survey carried out in San Giovanni mine near Iglesias (Sardinia, Italy), particularly in Santa Barbara and Santa Barbara 2 caves, the data post-processing and three-dimensional modelling of “point clouds” (operations performed witha dedicated software), and the use of the obtained digital model. Moreover, the paper describes the advantages of laser scanning for the hypogean survey in comparison to traditional methods and the future potentialities of a broad application of laser scanning instruments in caves.
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.
The Puerto Princesa Underground River (PPUR) is one of the largest subterranean estuaries in the world, where tides propagate over 7 km inside the cave. PPUR, consisting of over 30 km of giant ...galleries, hosts an extremely complex ecosystem based on huge colonies of bats and swiftlets. Its natural uniqueness was recognized as World Heritage by UNESCO in 1999, while the first part of its navigable branch was used as a show cave since over 20 years earlier. A peculiarity of this cave is that, even though it is visited by more than 300.000 people/year, no fixed structures have been placed inside it, which therefore should be still considered as a totally pristine cave. In the last few years, tourist pressure has been growing exponentially, and the first evidence of ecological problems have been noticed during the most crowded days. Therefore the Park Authorities decided to investigate how to manage the increasing tourism and limit the impact on the natural environment of the PPUR and its surrounding areas
The analytical problems of dating gypsum speleothems with the U-series technique are reviewed. Gypsum speleothems are, in general, very low in U content, challenging the limits of detection methods. ...Various approaches to dissolving gypsum and isolation of actinides from the matrix include ion-pairing dissolution with magnesium salts and using nitric acid. The most precise dating technique is Thermal Ionization Mass Spectrometry (TIMS), combined with Fe(OH)3 scavenging and anionic exchange chromatography. Less satisfactory, but much quicker, is direct retention of actinides from HNO3 by means of TRU resin and MC-ICP-MS detection. We have tested these methods on gypsum speleothems from the Sorbas karst in Spain and from the Naica caves in Mexico.
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•A petroleum exploration borehole accidentally lost drilling fluids in karst voids.•The Ba-Al-Fe- rich drilling fluids intercepted a main karst drain.•The drilling fluids acted as ...tracers in this extremely well-karstified aquifer.•A drinking water karst spring was polluted for weeks.•Barium continues to show up in the spring waters after rainfall episodes.
The area around Ragusa in Sicily is well known for the exploration of petroleum deposits hosted in Mesozoic carbonate rocks. These reservoirs are overlain by less permeable rocks, whereas the surface geology is characterized by outcrops of Oligo-Miocene carbonate units hosting important aquifers. Some of the karst springs of the area are used as drinking water supplies, and therefore these vulnerable aquifers should be monitored and protected adequately.
In the early afternoon (14:00) of 27 May until the late evening (19:30) of 28 May 2011, during the construction of an exploitation borehole (Tresauro 2), more than 1000m3 of drilling fluids were lost in an unknown karst void. Two days later, from 06:30 on 30 May, water flowing from Paradiso Spring, lying some 13.7kmSW of the borehole and 378m lower, normally used as a domestic water supply, was so intensely coloured that it was unfit for drinking.
Bulk chemical analyses carried out on the water have shown a composition that is very similar to that of the drilling fluids lost at the Tresauro borehole, confirming a hydrological connection. Estimations indicate that the first signs of the drilling fluids took about 59h to flow from their injection point to the spring, corresponding to a mean velocity of ∼230m/h. That Paradiso Spring is recharged by a well-developed underground drainage system is also confirmed by the marked flow rate changes measured at the spring, ranging from a base flow of around 10–15l/s to flood peaks of 2–3 m3/s.
Reflecting the source and nature of the initial contamination, the pollution lasted for just a few days, and the water returned to acceptable drinking-water standards relatively quickly. However, pollution related to heavy-mineral fines continues to be registered during flooding of the spring, when the aqueducts are normally shut down because of the high turbidity values. This pollution event offers an instructive example of how hydrocarbon exploitation in intensely karstified areas, where natural springs provide domestic water supplies, should be controlled effectively to prevent such disasters occurring. This pollution incident is also a useful example of how such “accidental” tracer tests can identify rapid karstic flowpaths over long distances.
Geomorphological studies have been carried out in rapidly evolving salt caves related to small watersheds in the San Pedro de Atacama area, Chile. Radiocarbon ages of bones and wood from cave ...deposits, combined with the presence of large salt caves, geomorphological and sedimentological observations, and the results of micrometer measurements outside and in some of the caves, suggest a period of speleogenesis in the Cordillera de la Sal during the onset of the Holocene, during which the large halite cave systems developed, followed by an early Holocene hyperarid period. Most smaller caves (i.e. Lechuza del Campanario) most probably formed at the start of the wetter mid-Holocene period (5–4.4 ka), when precipitation was never intense enough to entrain large amounts of sediments, but enough to trigger cave development. A diamicton in Lechuza del Campanario Cave radiocarbon dated at ca. 4.4 ka shows that at least one high intensity rainfall event occurred in this recharge basin during the mid-Holocene wet interval. A wet period with lower intensity rainfall events followed between 4.0 and 2.5 ka, causing the 4.4 kyrs old diamicton in Lechuza del Campanario Cave to be entrenched, and the alluvial fan at the downstream end of Palacio del Sal Cave to be covered with windborne sediments dated by OSL at around 3.6 ka. At ca. 2 ka there was a high-intensity rainfall event documented by the age of a twig stuck in the ceiling of the Palacio del Sal Cave, followed by a period with lower intensity rain events until ca. 1.3 ka, when another intense flood produced a mudflow that deposited a second diamicton in Lechuza del Campanario Cave. From then on clustering of radiocarbon ages for wood and bone recovered from caves indicates increased rainfall intensity in the period ca. 0.9–0.5 ka, followed by no registered events until a minor flood at ca. 0.13 ka. The four-centuries long wetter time interval (0.9–0.5 ka), corresponding to the Medieval Climate Anomaly, has been an archeologically important period in the Atacama Desert (Tiwanaku culture).
The observations and a detailed review of paleoclimate literature from this key area have allowed the development of a landscape evolution model related to changing climate conditions during the Late Holocene.
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•Salt caves have formed in the Atacama Desert even under hyperarid conditions.•Radiocarbon dating of bones and wood gives ages of debris flows (extreme events) in caves.•Micro Erosion measurements on salt outcrops in caves and outside provide additional data.•Salt cave geomorphology records flood events and changing hydrological conditions.•These data have led to a model for landscape evolution in changing climate conditions.
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