Karst Caves Research Articles

Evaluating karst features and geological fault leakage risks based on geophysical method in Dongzhuang reservoir area, Shaanxi

Leakage along faults, particularly in karst area faults, is a critical concern that can prevent impounding a reservoir. The Laolong Mountain fault in the Dongzhuang Reservoir Project Area in Shaanxi Province, China, is a large fault that may impede the project. To assess whether concentrated leakage can occur along this fault, we used a comprehensive approach involving footrill exploration, an electromagnetic method, optical imaging techniques, water pressure testing, and large-scale groundwater tracer tests. Footrill exploration results revealed that the karst features predominantly comprise karst cavities with some fissures and karst caves. These formations are typically clustered along fractures with a linear joint density of 0.4–1.5 joints/m. The linear karst rate was 0.39 %, and the karst cavities have small diameters of only a few centimeters and depths not exceeding 15 cm. A geophysical exploration indicated that low resistivity values (approximately 200 Ω·m) on the north side of the fault zone's hanging wall, with the lowest values being approximately 100 Ω·m. The fault's footwall was noted to have higher resistivity (approximately 2000 Ω·m). The rock properties on either side of the fault zone differ considerably. The upper plate of the fault (downstream of the river) has high-resistance carbonate rock formations with a well-preserved structure, whereas the lower plate (upstream of the river) comprises low-resistance sandstone and mudstone formations with notable fragmentation at the fault's surface compression zone. Tracer tests indicated an eastward groundwater flow from Zuantian Ridge toward the Jing River in the west. The results suggest that eastward leakage along the Laolong Mountain fault and its influence zone is unlikely upon reservoir impoundment. The geophysical exploration method in this study integrated and cross-validated the footrill exploration, hydrological test, groundwater tracing, optical imaging, and other methods; it can thus serve as a reference for future research.

Use of electrical resistivity tomography to reduce landfill siting risks in the south-central kentucky karst

Electrical Resistivity Tomography (ERT) can be a key tool for aiding in characterization of karst geohazard risks at proposed landfill sites. This study is proximal to the south-central Kentucky karst and Mammoth Cave National Park and possesses siliciclastic cap rock upland areas that pose relatively high groundwater-contamination risks due to adjacent ravines floored by carbonates. Complex stratigraphy associated with the Mississippian-Pennsylvanian unconformity and juxtaposition of heterolithic sedimentary rocks in general presents further challenges for demarcating hydrogeological characterization of the base of engineered landfills. A conceptual site model integrates ERT surveying and field geology that both satisfactorily characterize the site and risks to groundwater resources without conducting multiple borings. The proposed landfill site is compared to well-known and mapped caves at a landfill near Bowling Green, Crumps Cave near Smiths Grove, and River Styx Spring at Mammoth Cave. Our work entails review of ERT datasets at known cave sites and compares these to two ERT profiles that traversed the proposed landfill site, which are integrated with study of outcrops, and an excavated pit and trench. ERT data range from several low 10 s to about 400 Ω-meter values for mud rock units whereas sandy units possess ERT values from approximately 500 to several tens of thousands of Ω meters. The greatest values are indicative of basal Pennsylvanian Caseyville Sandstone, and these exceed 32,000Ω meters. In comparison, ERT values at known cave sites range from one to 100,000 Ω meters, with elevated, dry rock or possibly dry (air filled) caves interpreted from the greatest values and low values reflective of conductive underground cave streams and moist caves. An unexpected challenge specific to the Hart County landfill study includes occurrence of well-drained and highly weathered Caseyville at the highest elevations of the site causing increased electrical contact resistance during ERT surveying. The overall ERT contrast however, between quartz-rich and clay poor strata (high-resistivity rocks and regolith) and clay-rich strata (low-resistivity rocks) provides independent data consistent with the observed stratigraphy exposed in site exposures. Nonuniqueness of conductive intervals at the Hart County site contrasts with other conductive areas at depth associated with moist or wet cave passages as documented at Crumps Cave and Mammoth Cave.

Deep learning for predicting porosity in ultra-deep fractured vuggy reservoirs from the Shunbei oilfield in Tarim Basin, China

Deep and ultra-deep carbonate reservoirs in China, which account for 34% of the country’s oil and gas reserves, pose significant challenges for porosity prediction due to their complex geological features, including extensive burial depth, weak seismic signals, and high heterogeneity. To address these challenges, this study develops an advanced deep learning approach specifically designed for ultra-deep, fault-controlled, fractured-vuggy reservoirs in the Tarim Basin. The study utilizes a three-dimensional seismic dataset and applies Principal Component Analysis (PCA) to select five key features from eight seismic attributes. Additionally, seismic phase-controlled constraints are incorporated into the model. Using deep learning technology, a porosity prediction model for ultra-deep carbonate reservoirs has been constructed. Validation using blind wells from the Shunbei oilfield shows that this approach achieves a 76% reduction in Mean Square Error (MSE) compared to traditional impedance inversion techniques, highlighting its high predictive accuracy. Through SHapley Additive exPlanations (SHAP) analysis, the attributes LAMBDA_AAGFIL and PHASE_ANT are identified as the most influential, highlighting their importance in representing karst cave and fracture structures within the reservoir. These findings underscore the innovation and substantial improvement of the proposed method over conventional techniques, offering a robust and high-precision approach for porosity prediction in ultra-deep carbonate reservoirs.

The late Middle Pleistocene Zhongshan cave fauna from the Bubing Basin, southern China

The karstic caves in the Bubing Basin, Guangxi, southern China, contain abundant Quaternary mammalian fossils. These cave sites are located at varying altitudes that have been roughly correlated with chronological age (higher caves are older, lower caves are younger). A growing number of recent studies have established a regional biochronological sequence for these Bubing caves from the Early to the Late Pleistocene. Here, we describe a new mammalian assemblage from the Zhongshan Cave, that dates to the late Middle Pleistocene - Marine Isotope Stage 6 (191–130 ka). The age is supported by minimum ages derived from U-series dating of the deposits, and the ESR/U-series dating of one Rhinoceros tooth (∼184 ka). The Zhongshan mammalian assemblage, comprising 33 taxa of large-sized mammals, belongs to the Middle Pleistocene “Ailuropoda-Stegodon” faunal unit and, in this respect, most closely resembles the Ganxian fauna (362–168.9 ka). The high diversity and abundance of ruminant Artiodactyla (versus Perissodactyla) in the Zhongshan fauna suggest a diversity of forest to more open habitats in the Bubing Basin during this period.The Zhongshan fauna fills a gap in the biochronological framework of southern China, offering new insights into the evolutionary history of some mammalian lineages in the Bubing Basin. Overall, data indicate major changes in the Early to Late Pleistocene faunal sequence, particularly with more turnover during the Early-Middle Pleistocene transition compared to the Middle-Late Pleistocene transition.Comparison between faunas from the Bubing Basin with those from sites in the Chongzuo area, also in Guangxi, southern China, highlights two major phases in the general decline of large-sized mammals during the Middle to Late Pleistocene transitional period. In that respect, our results provide an updated biochronological background for further analyses of the region.

New vouchered and taxonomically verified records of cave-dwelling populations of catfishes of the genus Rhamdia (Siluriformes, Heptapteridae) from Costa Rica

Dedicated ichthyological surveys in two karstic caves in Costa Rica resulted in the discovery of hypogean populations from three epigean species of catfishes of the genus Rhamdia. The taxonomic identity of these populations was initially determined based on morphological traits and subsequently corroborated with comparative DNA sequence data in a phylogenetic framework. Individuals from all hypogean populations documented herein exhibit only partial troglomorphism, characterized by only moderate (vs. complete) integumentary depigmentation without extreme eye reduction/loss. A similar pattern of incomplete troglomorphism at the individual level has been observed in other cave-dwelling species/populations of Middle American Rhamdia, and tentatively attributed to gene flow with and/or incipient speciation from epigean lineages. Since most hypogean forms of Rhamdia derive from/are part of a larger clade of primarily R. laticauda, our discovery of cave-dwelling populations assignable to R. nicaraguensis and R. guatemalensis is noteworthy, particularly in the case of the former, which represents the first taxonomically verified record of a cave-dwelling population of this epigean species. Among our findings is the remarkable discovery of hypogean populations from two different species of Rhamdia (R. laticauda and R. nicaraguensis) inhabiting the same cave (Gabinarraca). This finding is particularly significant because it represents the first time that cave-dwelling populations from different species of Rhamdia are reported to be living in syntopy. Continued discovery of cave-dwelling populations during targeted ichthyological surveys reinforces the notion that our understanding of the diversity of hypogean Rhamdia is incomplete and that sustained exploration and taxonomically sound documentation work are paramount to advancing knowledge about the diversity and evolution of these group of Neotropical catfishes.

Diversity pattern and antibiotic activity of microbial communities inhabiting a karst cave from Costa Rica.

The studies of cave bacterial communities worldwide have revealed their potential to produce antibiotic molecules. In Costa Rica, ~400 caves have been identified; however, their microbial diversity and biotechnological potential remain unexplored. In this work, we studied the chemical composition and microbial diversity of a Costa Rican cave (known as the Amblipigida cave) located in Puntarenas, Costa Rica. Additionally, through culture-dependent methods, we evaluated the potential of its microbiota to produce antibiotic molecules. Mineralogical and elemental analyses revealed that the Amblipigida cave is primarily composed of calcite. However, small variations in chemical composition were observed as a result of specific conditions, such as light flashes or the input of organic matter. The 16S rRNA gene metabarcoding revealed an extraordinarily high microbial diversity (with an average Shannon index of ~6.5), primarily comprising bacteria from the phyla Pseudomonadota, Actinomycetota, Firmicutes and Acidobacteriota, with the family Pseudomonadaceae being the most abundant. A total of 93 bacteria were isolated, of which 15% exhibited antibiotic activity against at least one Gram-positive or yeast strain and were classified within the genera Lysobacter, Streptomyces, Pseudomonas, Brevundimonas and Bacillus. These findings underscore the highly diverse nature of cave microbiota and their significant biotechnological potential, particularly in the production of antibiotic compounds.

Cave morphology and moonmilk deposits of Ryongmun Cavern, Democratic People’s Republic of Korea: A Study for the Conservation of Natural Heritage

The Ryongmun Cavern, registered on the World Heritage Tentative List, is the largest and most beautiful karst cave on the Korean peninsula. The characteristics of the cave morphology and moonmilk deposits in the Ryongmun Cavern were studied. A cross section of the main direction of the cave shows that the Ryongmun Cavern is made up mainly of four strata and this caused 4 stages of decline in underground waterline in the course of cave formation. The cave is mainly characterized by NW–SE-trending, NWW–SEE-trending and NNE– SSW-trending passages. The horizontal passages usually have large and wide spaces, whereas the inclined ones are relatively small and narrow. The cave minerals in the Ryongmun Cavern are mainly calcite and aragonite. In the cave, stalactites, stalagmites, limestone columns, cave pearls, etc. Are calcite; and, anthodites are aragonite. In the cave, speleothems display a wonderful underground landscape in harmony with the cave bedrock and groundwater (streams, waterfalls and ponds). The main scenes of the underground karst landscape in the cave are stalactites, stalagmites, limestone columns, stone waterfalls anthodites, underground waterfalls, and underground ponds.The deposits that have been formed recently on the surface of speleothems and walls in the cave are mainly moonmilk composed of hydromagnesite (Mg5(CO3)4(OH)2•4H2O) with an average particle size of 0.55 μm and chemical composition of MgO–29.43% and CaO–6.28%. The moonmilk is present in a white, fine powder form, a hand-rubbed smooth, and a moisture content of 42.0%. Also, the pH is 10.09, which is alkaline. In the Ryongmun Cavern, moonmilk was formed at sites with very low supply of karst water and relatively high wind speeds. The unique underground karst features provide sufficient evidence for geoheritage value of the cave and the characteristics of moonmilk provide a significant implication for management and preservation of the cave environment.

Roosting ecology, reproduction, and population fluctuations of three Hipposideros species (Chiroptera) in Indonesian caves

Abstract Hipposideros spp. are insectivorous bats and karst cave dwellers. This study aimed to study the roosting ecology, reproduction, and population fluctuations of three species H. diadema, H. larvatus, and H. ater in Gunung Sewu Karst region, Indonesia. Age and reproductive status of individuals were identified and analyzed using a combination of forearm length (FA) and body mass grades (W). Multiple regression analysis was used to determine the correlation between population size, rainfall and population structure based on FA, reproductive status, and W. Crude birth rate (CBR) and general fertility rate (GFR) were used to determine the population’s birth rate and female fertility. The results showed that the population of the three Hipposideros species were quite stable over the year with a peak in January which classified them as monoestrous, with mating, pregnancy, and lactation occurring once a year with no delay between mating and pregnancy. Pregnancy lasted 8–12 weeks and lactation 4–5 weeks. The population structure of the three species tended to be stable over the year. The CBR and GFR values can be used for rapid assessment guidelines in an area.

Implementation of complementary methods for bat sampling in a karstic landscape in central–northern Guatemala, Central America

The use of complementary sampling methods for bats is recommended to improve inventories of species. Here we performed direct and indirect sampling in caves, in the main river, and in various forest vegetation covers in a karst landscape in central–northern Guatemala. We determined efficiency and complementarity between methods. Using mist nets and with an effort of 2,670 m²h, we captured 296 individuals of 19 species. Using ultrasonic microphones and after 71 hours of recording, we obtained 1,598 effective files of 16 species/sonotypes. Using a harp trap and after 79 hours of operation, we captured 939 individuals of 12 species. In total, we report 34 species/sonotypes. Regarding the percentage of species richness sampled, according to an extrapolation to double the sampling effort, this varied between 69.8 % and 91.5 %, which we consider satisfactory. The percentages of complementarity between methods were over 70 %, notably high between mist nets and ultrasonic microphones (91 %). To date in Guatemala, inventories have been incomplete, mainly because they are biased by the use of mist nets and the capture of bats of the Phyllostomidae family. Training and implementation of non–extensively used methods such as acoustic detection is needed to improve our knowledge about this taxonomic group and provide fundamental information for conservation strategies. Dataset published through GBIF (DOI: 10.15470/3vcvof). Key words: Harp trap, Karstic caves, Lanquín, Mist nets, Riparian environments, Ultrasonic microphones

Reservoir characteristics and distribution of the Majiagou Formation in the Fuxian area of Ordos Basin, China

The Majiagou Formation in the Fuxian area of the southeastern Ordos Basin has undergone a complex diagenetic evolution history under the influence of eustacy and the Caledonian karstification, resulting in several complex reservoir types. Through analyses of mineralogy, petrology, and reservoir geology, three major types of dolomite reservoirs with different genetic mechanisms, including anhydritic moldic-dissolved pore type, dolomitic intercrystalline-pore type, and fractured type were identified, and their formation mechanisms and distribution patterns were examined. The aphanocrystalline to very fine-crystalline anhydritic dolomite was resulted from Sabhak dolomitization, and is characterized by small size of crystals and high content of anhydrite. Dolomite reservoirs of anhydritic moldic-dissolved pore type were developed in multi-stage dissolution processes and mainly distributed at higher positions of the paleogeomorphology where the filling was weak. The very fine to fine-crystalline dolomite of shoal facies was formed under seepage-reflux dolomitization, and characterized by larger sizes of crystals and well-developed intercrystalline pores. Dolomite reservoirs of intercrystalline-pore type were mainly developed at the lower positions of the paleogeomorphology where bedding-parallel karst dissolution was strong. The fractured dolomite reservoirs, generated by the anhydrite swelling and karst cave collapse, occur in multiple horizons but within limited areas due to multi-stage fillings.

Performance Evaluation of Directional Porous Oil Storage Medium Fabricated by PTFE and Naphthalene

Porous oil storage media is the core of self-lubricating rolling functional components. The internal pore directivity of porous oil storage media is different，and it reduces the utilization rate of lubricating oil. In this paper, a new fabrication method of porous oil storage media with directional pores is carried out, and the properties of the porous media, such as hardness, density, porosity, oil storage rate and oil retention rate are evaluated. The experimental results show that the fabrication pressure has a linear positive effect relationship with the hardness of the porous media, and has no significant effect on the density, porosity, oil storage rate and oil retention rate. The mass fraction of pore former has a linear negative effect relationship with the hardness and density of the porous media, and a linear positive effect relationship with the porosity the greater the mass fraction of pore former, the greater the initial oil seepage rate of oil rejection. The internal pores of the porous media have a fibrous structure of the karst cave type, and the internal pores are interconnected and have good orientation. This study aims to provide a lubricating theoretical reference for the fabrication of porous oil storage media.

Deciphering rock surface origins in a karst cave: insights from the Rača Cave, Lastovo, Croatia

This paper outlines a comprehensive fieldwork methodology for discerning the origin of rock surfaces within a karst cave environment. This methodology is particularly utilized in a cave with breakdown morphology. Using Rača Cave in Lastovo, Croatia as a case study, we explore geological and morphological features through advanced surface analysis. The approach involves meticulous measurement of rock discontinuities, joint patterns, and surface formations. Cost-efficient and time-efficient data collection and processing during field-work were undertaken with FieldClino Move and Polycam applications on smartphones. Visualization techniques were employed to elucidate the interplay between erosion, deposition, and speleogenetic processes.

Nine new spider species of Belisana Thorell, 1898 (Araneae, Pholcidae) from karst caves, with a list of species of the genus from Guizhou, southwestern China.

Species of the spider genus Belisana Thorell, 1898 exhibit high diversity in Guizhou, southwestern China. Previously, only eight species of Belisana were recorded in Guizhou. In this study, nine new species are described from karst caves: Belisanabijie Wang, S. Li & Yao, sp. nov., B.liupanshui Wang, S. Li & Yao, sp. nov., B.majiang Wang, S. Li & Yao, sp. nov., B.nayong Wang, S. Li & Yao, sp. nov., B.qixingguan Wang, S. Li & Yao, sp. nov., B.xiuwen Wang, S. Li & Yao, sp. nov., B.yongcong Wang, S. Li & Yao, sp. nov., B.zhouxi Wang, S. Li & Yao, sp. nov., and B.zunyi Wang, S. Li & Yao, sp. nov. Belisanazhangi Tong & Li, 2007 is reported from Guizhou for the first time. In addition, a list of all species of Belisana from Guizhou is provided.

Large non-karst caves of the Altai-Sayan mountain region: morphology and genesis

In the Altai-Sayan mountain region, located in southern Siberia, there are a number of caves developed in rocks in which karst processes are impossible to occur. In East Sayan, these are the Big Oreshnaya and Dudinskaya caves, the total length of which is more than 50 km and 35 km, respectively. Within the Altai Mountains, these are the Altaiskaya and Kek-Tash caves with a total length of 4.7 and 3.2 km, respectively. Mapping of the listed caves revealed that the morphology of their passages and the general structure differ significantly from those of caves in carbonate rocks. The passages have a flattened shape in cross section. Their width is usually meters and tens of meters, vertical extension is tens and hundreds of meters, and lateral extension is hundreds of meters. In general, the pattern of the passages is arranged in a box-like structure, where the pasages fit into a system of disjoint extended subvertical planes with rare short subvertical planes connecting them. The structure of the passages of the studied caves resembles the structure of karst caves, rotated vertically by 90°. The main directions of the passages there are not aligned in subhorizontal planes, but in subvertical ones. The revealed structure corresponds to the geometry of the structural pattern of Late Cenozoic fault systems formed as a result of subhorizontal compression. Signs of abundant argillization (alteration of the initial substance by hydrothermal processes and its replacement by newly formed clay minerals) were found in the studied caves. The formation mechanism of the studied caves is offered: removal of the substrate argillized by hydrothermal processes along the fault zones, by groundwater without significant participation of karst processes.

Study on field and numerical analysis of karst collapse as railway hazard

The vulnerability of karst ecosystems and the weak mechanical performance of caves pose hidden risks in railways, leading to increased karst collapses. To analyse karst collapse as a railway hazard, the Beijing–Guangzhou railway line in China was selected to identify karst features, using the multi-source frequency domain method because of its operational advantages. Abaqus was also used to numerically analyse the factors (dynamic loading, groundwater fluctuations, over-burden thickness) affecting the collapse mechanism. The study reveals diverse stratigraphy, transitioning from a Quaternary layer to stable rock formations. A notable finding is that the presence of a karst cavity in the railway embankment significantly increases the vertical dynamic displacements, particularly within the soil layer, by 72%, highlighting the significant impact of karst sections on soil dynamics. The study also reveals that due to the groundwater table fluctuations from the subsoil surface to the subgrade surface, the maximum displacement increases by 73% in the subgrade section of the railway embankment. The authors consider soil overburden thickness to validate confirmation of reliability through field data and theoretical study. The findings offer crucial insights for managing karst hazards, enhancing railway safety and ensuring durable infrastructure in challenging geological conditions.

A New Method for Determining the Safety Distance Between Irregular Karst Cave and Circumferential Shield Tunnel

ABSTRACTWhen a shield tunnel passes through a karst area, the water‐filled cave can easily make the surrounding rock metamorphic, resulting in water inrush, ground collapse, and shield machine failure and other engineering hazards. Natural cavities have a significant degree of geometric irregularity due to groundwater alteration and soluble rock erosion. Considering the difficulties in describing the shape of a natural irregular cavity, circular, rectangular, and elliptical geometries have been simplified in most related studies. Based on the upper bound theorem of limit analysis, we established a three‐dimensional failure model including the karst caves located directly above and below the circumferential side of the tunnel. Then, we deduced the corresponding analytical solution of the critical safety distance (CSD). Furthermore, the effects of rock mass parameters, cave parameters, and geometric parameters on the CSD were analyzed. Then we designed the numerical simulation considering the irregular geometry shape at the circumferential side of tunnel using the Fourier descriptors. In addition, we estimated the CSDs for two failure models using the revised dichotomy and failure criterion. The findings demonstrated a quantifiable association between CSD and Fourier descriptors of irregular cave shape, resulting in the development of a CSD prediction model. These test results can provide a theoretical foundation and direction for predicting water inrush caused by the constrained irregular cave.

Formation of vertical columnar seismic structures and seafloor depressions by groundwater discharge in the drowned Miami Terrace platform and overlying deep-water carbonates, southeastern Florida

The presence of vertical cross-formational fluid migration passageways within sedimentary basins can profoundly impact aquifer and reservoir fluid-flow and their identification is fundamental to informing management of subsurface fluid resources (groundwater, oil, gas). In an onshore and offshore southeastern part of Florida, 2D/3D seismic-reflection and bathymetry data document ∼153 vertical columnar structures composed of reflection disruptions up to 790 m in the height and averaging 360 m in diameter, and ∼219 subcircular to circular seafloor depressions up to 1334 m wide. Our study focuses on these features found within the offshore shallow-marine carbonate Miami Terrace platform, which drowned approximately at the end of the middle Miocene, and within overlying Plio-Quaternary deep-water carbonate slope and drift deposits. Most columnar structures are rooted in stratiform aquifers of the Miami Terrace platform and associated with faults or fault intersections produced by Eocene and circa late Miocene tectonics. The columns commonly terminate within the platform or as subcircular depressions along an amalgamated karstic and drowning unconformity at the platform top. The columns typically stretch upwards from a zone of deep karst cavity collapse through the Miami Terrace platform with upward decreasing sag on internal reflections. Following drowning and Plio-Quaternary partial burial of the Miami Terrace platform by deep-water deposits, the subcircular depressions and faults along the platform top were points of origin for a second phase of column growth upward into the deep-water deposits. The continuation of deep platform cavity collapse and column evolution produced pockmarks along paleo-seafloors within the deep-water deposits and at the present-day sea floor. The Plio-Quaternary pockmarks formed at water depths too deep to suggest an origin related to meteoric karst above or near sea level, but rather their formation is suggested to be related to cyclic sea level falls that drove increased groundwater head and density gradients, and seafloor discharge of offshore freshened groundwater sourced from the underlying platform. Plausibly, mixing of freshened groundwater and seawater at the seafloor discharge sites drove dissolution of the host deep-water deposits, which together with erosion by groundwater venting and current scouring formed the pockmarks.Seaward of the Plio-Quaternary seafloor pockmarks, at the late-middle Miocene upper slope of the Miami Terrace platform and along the regional karst/drowning unconformity is a slope-parallel band of ∼189 densely distributed subcircular seafloor depressions with diameters up to 1334 m at water depths up to ∼660 m. It is plausible that along the upper slope, faults and fractures produced by gravity-driven slope instability and possibly tectonics formed a dense network of fluid passageways that promoted upward artesian freshened groundwater flow to sites of discharge where mixing with seawater generated limestone dissolution and the depressions. But tectonic uplift may have forced emersion and initial meteoric sinkhole formation circa late Miocene with later enhancement by freshened groundwater discharge and bottom current erosion.

Contributions of DNA Sequencing Technologies to the Integrative Monitoring of Karstic Caves

Contributions of DNA Sequencing Technologies to the Integrative Monitoring of Karstic Caves

NEW CAVERNICOLOUS SPECIES OF THE GENUS CHALLIA BURR, 1904 (DERMAPTERA: PYGIDICRANIDAE, CHALLIINAE) FROM CHINA

A new species of the genus Challia Burr, 1904 (Dermaptera: Pygidicranidae, Challiinae), Challia guilinensis sp. n., is described and illustrated based on male from a karst cave in China. The new species differs from the congeners by the morphology of forceps and genitalia. Holotype is deposited in the Insect Collection of Jiangsu University of Science and Technology, Jiangsu Province, China.

Using hydrochemistry and stable isotopes to character the karst water environment in a cave site, South China

For cave sites located within the seasonal fluctuation zone of groundwater, obtaining a comprehensive understanding of the hydrogeological conditions and hydrochemical environment is of utmost importance in assessing the preservation of cultural deposits. However, due to the heterogeneity of karst development, the hydrochemical environment of the overburden karst water-bearing unit may exhibit complex variations. In this study, the characteristics of the water environment in a foot cave system and its surrounding aquifer were investigated at the Zengpiyan site, employing hydrochemistry, hydrogen and oxygen isotope analysis, as well as sulfate isotope analysis, in conjunction with the hydrogeological background. Based on the exposure of the karst cave and the groundwater flow conditions, the water-bearing medium was categorized into five types. The aquifer exhibited either an oxidation or reduction condition, with a distinct “dissolved oxygen hole” observed in the saturated zone of the cave site. Ion concentration analysis revealed that the groundwater was influenced by the prior accumulation of cinders in the upstream region, leading to sulfate contamination within the foot cave system. However, during the groundwater movement from upstream to downstream, the attenuation rate of pollutants displayed significant variations. Notably, the sulfate content was unusually low within the site cave. Hydrogen and oxygen isotopes provided insights into the differing circulation and movement velocities of groundwater within the local environment. Additionally, sulfate isotopes confirmed the sources of sulfate and the occurrence of bacterial sulfate reduction within the site cave. Consequently, an environmental zoning classification was established based on these analyses. Although the concentration of dissolved ions appears low in the anoxic area, it does not imply a diminished environmental risk. Under reducing conditions, these pollutants can be converted into more aggressive gases, posing a substantial threat to the preservation environment of cave sites. Therefore, sufficient attention should be given to this aspect in order to ensure adequate protection.