Acta CarsologicaOpen Journal SystemsJournal HelpUserUsername Password Remember meNotifications View SubscribeEnglish Slovensko (Slovenian)Journal ContentSearchSearch ScopeBrowse By Issue By Author By ...Title Other JournalsFont SizeMake font size smallerMake font size defaultMake font size larger Home About Login Register Search Current Archives Announcements Submit Old SiteHome > Vol 44, No 3 (2015) > AudraResearch frontiers in speleogenesis. Dominant processes, hydrogeological conditions and resulting cave patternsPhilippe Audra, Arthur N. PalmerDOI: https://doi.org/10.3986/ac.v44i3.1960AbstractSpeleogenesis is the development of well-organized cave systems by fluids moving through fissures of a soluble rock. Epigenic caves induced by biogenic CO2 soil production are dominant, whereas hypogenic caves resulting from uprising deep flow not directly connected to adjacent recharge areas appear to be more frequent than previously considered. The conceptual models of epigenic cave development moved from early models, through the “four-states model” involving fracture influence to explain deep loops, to the digital models demonstrating the adjustment of the main flow to the water table. The relationships with base level are complex and cave levels must be determined from the elevation of the vadose-phreatic transitions. Since flooding in the epiphreatic zone may be important, the top of the loops in the epiphreatic zone can be found significantly high above the base level. The term Paragenesis is used to describe the upward development of conduits as their lower parts fill with sediments. This process often records a general baselevel rise. Sediment influx is responsible for the regulation of long profiles by paragenesis and contributes to the evolution of profiles from looping to water table caves. Dating methods allow identification of the timing of cave level evolution. The term Ghost-rock karstification is used to describe a 2-phase process of speleogenesis, with a first phase of partial solution of rock along fractures in low gradient conditions leaving a porous matrix, the ghost-rock, then a second phase of mechanical removing of the ghost-rock mainly by turbulent flow in high gradient conditions opening the passages and forming maze caves. The first weathering phase can be related either to epigenic infiltration or to hypogenic upflow, especially in marginal areas of sedimentary basins. The vertical pattern of epigenic caves is mainly controlled by timing, geological structure, types of flow and base-level changes. We define several cave types as (1) juvenile, where they are perched above underlying aquicludes; (2) looping, where recharge varies greatly with time, to produce epiphreatic loops; (3) water-table caves where flow is regulated by a semi-pervious cover; and (4) caves in the equilibrium stage where flow is transmitted without significant flooding. Successive base-level drops caused by valley entrenchment make cave levels, whereas baselevel rise is defined in the frame of the Per ascensum Model of Speleogenesis (PAMS), where deep passages are flooded and drain through vauclusian springs. The PAMS can be active after any type of baselevel rise (transgression, fluvial aggradation, tectonic subsidence) and explains most of the deep phreatic cave systems except for hypogenic.
This edited work presents an interdisciplinary exploration of the use of caves and rock shelters across Europe during the medieval period for a wide range of religious and spiritual purposes by ...Christian, Muslim, Pictish and non-denominational communities, at both regional and local levels.
Kahf Kharrat Najem Cave is a small cave in United Arab Emirates (UAE) that hosts a bat colony which is the source of guano deposits and peculiar centimeter-long yellowish stalactites. The mineralogy ...and geochemistry of these deposits were analyzed using powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopic microanalysis (EDX), scanning electron microscope (SEM), and stable isotope composition (δ^sup 13^C and δ^sup 15^N). Urea CO(NH^sub 2^)^sub 2^ was found to be the main compound of these stalactites, while allantoin C^sub 4^H^sub 6^N^sub 4^O^sub 3^ was found to be an accessory urea byproduct. This paper is the first to mention allantoin in a cave environment. We also identified rare sulfate minerals (aphthitalite, alunite) and phosphates that probably correspond to the archerite-biphosphammite series. The occurrence of these rare bat-related minerals is due to the extremely dry conditions in the cave, which accounts for the extraordinary preservation of the guano deposits and allows for the crystallization of these very soluble minerals.
Guano is a typical deposit found in caves derived from the excretions of bats and in minor cases of birds. These organic deposits decompose and form a series of acid fluids and gases that can ...interact with the minerals, sediments, and rocks present in the cave. Over sixty phosphates are known and described from caves, but guano decay also often leads to the formation of nitrates and sulfates. In this study twenty-two European caves were investigated for their guano-related secondary minerals. Using various analytical techniques, seventeen phosphates, along with one sulfate (gypsum), were recognized as secondary products of guano decay. Among those minerals, some are very rare and result from the interaction of guano leachates with clays, fluvial deposits, or pyrite. Some of these minerals are even found only in the studied caves (spheniscidite, robertsite). The most common minerals belong to the apatite group. The common mineral association present in fresh decaying guano is brushite-ardealite-gypsum, minerals that usually are not present in older deposits because of their higher solubility. Most minerals are in hydrated form because of the wet cave environment; however, some specific dry conditions may favor the presence of dehydrated minerals, such as berlinite, formed during guano combustion. Investigation on the acidity of guano piles shows pH values as low as 3.5 with an increase of acidity with age and depth. Finally, cave guano deposits should be better studied in the future because of their role in paleoenvironmental and paleoclimatic reconstructions and because it is important to better understand the origin of guano-related minerals, especially the phosphates and sulfates. Among all of the caves studied, Corona 'e sa Craba (Italy) and Domica-Baradla Cave (Slovakia-Hungary) are considered to be outstanding sites with respect to their phosphate mineralogy.
Patterned ground is a characteristic periglacial landform in polar and alpine environments but has not been systematically studied in karst caves. Here we characterize the periglacial environment and ...sorted stripes within the Ledenica pod Hrušico ice cave, western Slovenia. The stripes were mapped, sediment depth and grain size were measured, and cave and outside air temperatures were monitored together with ground temperatures. Eleven sorted stripes of coarse limestone debris had developed on 1 m thick silt‐rich sediment, underlain by limestone bedrock. Silt‐rich cave sediments can accumulate as insoluble carbonate residue or during flood events, whereas coarse debris may result from frost shattering. Cold winter air entered the ice cave, but little air exchange occurred during summer, when the cave air temperature slowly rose to a maximum of 5°C. Winter temperature oscillations propagated efficiently to the snow‐free cave floor. Fourteen freeze‐thaw cycles were observed at the patterned‐ground surface during winter 2015/2016 and may cause the differential frost heaving necessary for sediment sorting. Such periglacial conditions and mixtures of silty and coarse sediments can produce sorted patterns in karst caves.
Hermannshohle is a show cave located near Kirchberg/Wechsel in Lower Austria. Together with three nearby and genetically connected caves, it forms the Hermannshohlen cave system (HHS). With a length ...of 5 km, the HHS is the longest cave in the Lower Austroalpine unit. It is arranged as an extreme three-dimensional maze on a ground area of 200 x 200 x 82 m. Speleothems are abundant in this cave and represent the focus of this study. Low carbon isotope values indicate the presence of a soil-covered catchment above the HHS during times of speleothem deposition. 28 samples were dated by the ^sup 230^Th/U-method and, in combination with palaeomagnetic data from a 5 m-high sediment profile, indicate multiple phases of sediment infill and erosion in the HHS. Although parts of the cave system are nowadays located at or below the level of the nearby Rams brook, they fell dry already at least 125 ka ago.
Cave hosted ice bodies have been reported to suffer significant mass loss worldwide. Although some successful achievements were reported recently to confirm the potential of stable isotope, pollen or ...trace element records in cave glaciers for climate and environmental reconstructions, these archives are still weakly studied. This brief paper is to be an invitation to the geoscience community to face this research need and devote more scientific attention to the complex research of cave ice deposits before accelerated melt will determine the complete loss of the unique palaeoenvironmental information stored in these deposits.
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The Altai region of Siberia was inhabited for parts of the Pleistocene by at least two groups of archaic hominins-Denisovans and Neanderthals. Denisova Cave, uniquely, contains stratified deposits ...that preserve skeletal and genetic evidence of both hominins, artefacts made from stone and other materials, and a range of animal and plant remains. The previous site chronology is based largely on radiocarbon ages for fragments of bone and charcoal that are up to 50,000 years old; older ages of equivocal reliability have been estimated from thermoluminescence and palaeomagnetic analyses of sediments, and genetic analyses of hominin DNA. Here we describe the stratigraphic sequences in Denisova Cave, establish a chronology for the Pleistocene deposits and associated remains from optical dating of the cave sediments, and reconstruct the environmental context of hominin occupation of the site from around 300,000 to 20,000 years ago.
Orbital to millennial‐scale variations in Asian monsoon speleothem δ18O have been widely interpreted as records of monsoon intensity and/or rainfall amount. To assess the influence of these and other ...mechanisms on higher‐frequency δ18O variability, we utilize simulations from a spectrally nudged isotope‐enabled general circulation model coupled with instrumental climate data to investigate the climatic controls on interannual precipitation δ18O (δ18Op) variability at four key cave locations affected by the Asian monsoon: Qunf Cave, Oman; Mawmluh Cave, India; Tham Mai Cave, Laos; and Dongge Cave, China. Comparison with instrumental climate data shows that interannual δ18Op variations are only weakly related to local precipitation amount at the four sites and are instead controlled primarily by large‐scale monsoon intensity and upstream precipitation over the tropical Indo‐Pacific region, which influence the δ18O of incoming moisture. Spatial correlations with sea surface temperature and precipitation, composite analyses, and time series analyses show that the El Niño–Southern Oscillation (ENSO) also plays a key role in modulating interannual precipitation δ18Op variability in the region, especially in northern India and Southeast Asia, with positive δ18Op anomalies during El Niño years reflecting increased contribution of high δ18O moisture from the nearby Bay of Bengal. Coherent interannual to decadal δ18O variations seen in high‐resolution proxy records from across the Asian monsoon region, likely record monsoon intensity and upstream rainout, whereas ENSO related variability is likely to be strongest in records from northern India and Southeast Asia, with the largest anomalies expected when weak monsoons and El Niño occur together.
Key Points
Coherent variations in precipitation oxygen isotopes in the Asian monsoon region likely reflect monsoon intensity and upstream rainout
ENSO variability may explain incoherent interannual variations in oxygen isotope proxy records across the Asian monsoon region
Proxy records from North India and SE Asia should show strong positive oxygen isotope anomalies when weak monsoons and El Niño occur together
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