Cave Morphology Research Articles

Neotectonic movements in the Prut River valley: records in karst and river terrace deposits

The section of the Prut River valley between the villages of Dranytsia (Ukraine) and Cryva (Republic of Moldova) constitutes the southern part of the Khotyn-Mamalyga tectonic uplift. This is the only section within the valley where the Neogene gypsum layer is exposed by erosion of the Prut River and its tributaries. The polygonal structures (“parquet”) at three levels were found in clay deposits of the Popeliushka Cave. At present, the water table has been decreased by pumping up to 28 m from the natural level in the nearby gypsum quarry. However, the natural water table is only 4 m below the roof of the gypsum strata. The polygonal structures caused by dehydration are evidence that, in the past, the natural water table was at least 6 m lower than it is now. The radiocarbon-dated bone remains of woolly rhinoceros that were found in the Malimon-Canyon Cave, not far from Popeliushka Cave, show us that near 38 ky BP, this tectonic block, which contains both caves, was approximately 10 m higher than now, and slowly descended since that time. The terrace deposits on the Mamalyga tectonic block were dated to the end of the Early Pleistocene (Martonosha-Sula Stage), but due to the tectonic descending during the Late Pleistocene, this terrace is much lower than the average height of this terrace in the Prut Valley. Based on the analysis of the morphology of caves, cave deposits, and sections of terrace deposits, it was concluded that the Mamalyga and Cryva tectonic blocks in the Prut Valley underwent slow subsidence during the Late Pleistocene. At previous stages, the gypsum layer in both blocks was hypsometrically higher and was in the zone of groundwater level fluctuations. The surfaces of the floodplain terraces within these blocks are significantly deformed, and their current height does not correspond to the expected average for the Prut Valley. In the late Pleistocene–Holocene, an exceptionally powerful seismic event occurred in the region, which caused the liquefaction of the Lower Baden sands and their injection upward along the section. Key words: gypsum karst; cave sediments; river valley; tectonic movements; terrace levels; paleogeomorphological analysis; Prut River.

Graphene oxide and hydroxyapatite-based composite extracted from fish scale: Synthesis, characterization and water treatment application

In this study the removal of hydrocarbon pollutants from refinery waste water has been described through a convenient adsorption technique using a novel composite of graphene oxide (GO) and n-hydroxyapatite (n-HAp). The main aim was to synthesized composite which are not only sustainable and biodegradable but also exhibit high adsorption capacity and selectivity for hydrocarbon pollutants. Both the HAp and GO were synthesized from fish scales in the laboratory. The synthesized material was then characterized by XRD, FTIR, SEM, and EDX. At 40 °C and 80 min of reaction time, the adsorbent utilized in a batch mode study attained a maximum 97 % organic pollutant adsorption rate. The adsorption activity was spontaneous, exothermic, useful, and it adhered to the pseudo-2nd order kinetic model. without noticeably losing its activity, the adsorbent retained a high level of efficiency over four consecutive cycles. Adsorption of hydrocarbon wastes using composite adsorbent was carried out under batch mode of adsorption experiments. We also studied the effect of dose, temperature, time and pH of the solution on adsorption. Ethanol was used to regenerate the adsorbent, and it was then dried at 70 °C for re-use. The SEM investigation showed that the morphology of huge caves is rough, layered, and wrinkled. The oxygen and phosphate containing groups were found via FT-IR analysis. Freundlich and Langmuir kinetic models were used to measure the adsorption behavior by applying them to the adsorption data. The results demonstrated a strong correlation between the Freundlich isotherm model and the real data. This study showed a highly effective and cost-efficient methodology for the removal of toxic hydrocarbon contaminants in refinery wastewater.

CO2 Emission from Caves by Temperature-Driven Air Circulation—Insights from Samograd Cave, Croatia

Opposite to atmospheric CO2 concentrations, which reach a minimum during the vegetation season (e.g., June–August in the Northern Hemisphere), soil CO2 reaches a maximum in the same period due to the root respiration. In karst areas, characterized by high rock porosity, this excess CO2 seeps inside caves, locally increasing pCO2 values above 1%. To better understand the role of karst areas in the carbon cycle, it is essential to understand the mechanisms of CO2 dynamics in such regions. In this study, we present and discuss the spatial and temporal variability of air temperature and CO2 concentrations in Samograd Cave, Croatia, based on three years of monthly spot measurements. The cave consists of a single descending passage, resulting in a characteristic bimodal climate, with stable conditions during summer (i.e., stagnant air inside the cave) and a strong convective cell bringing in cold air during winter. This bimodality is reflected in both CO2 concentrations and air temperatures. In summer, the exchange of air through the cave’s main entrance is negligible, allowing the temperature and CO2 concentration to equilibrate with the surrounding rocks, resulting in high in-cave CO2 concentrations, sourced from enhanced root respiration. During cold periods, CO2 concentrations are low due to frequent intrusions of fresh external air, which effectively flush out CO2 from the cave. Both parameters show distinct spatial variability, highlighting the role of cave morphology in their dynamics. The CO2 concentrations and temperatures have increased over the observation period, in line with external changes. Our results highlight the role of caves in transferring large amounts of CO2 from soil to the atmosphere via caves, a process that could have a large impact on the global atmospheric CO2 budget, and thus, call for a more in-depth study of these mechanisms.

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.

Sediment load with metallurgical slag admixture under diverse morphological conditions along submerging karst stream

This study investigates the clastic fluvial sediments of the Jedovnický submerging stream in the section between the Jedovnice village and Křtinský stream (Moravian Karst, Czechia). A total of 28 samples were collected to analyze clast composition, slag content, grain size, and roundness. The sediment primarily consists of allochthonous Lower Carboniferous material (greywackes, clayey shales) with varying amounts of metallurgical slag, occasionally mixed with autochthonous deposits such as rockfall accumulations and tailings from the excavation of connecting adits. The slag content fluctuates, peaking downstream of the erosive section of the Rudické propadání cave, near the Stará řeka passage connection. Grain size distribution is influenced by both surface and cave morphology, as well as hydraulic conditions. The alternation between erosive and depositional zones, along with the unique karstic and speleorelief features, plays a crucial role in clast mobilization. These features include ponors, erosive and paragenetic corridors, sumps, and rockfalls. Fine particle accumulations are particularly noticeable in front of sumps or dams. Throughout the studied section, the proportion of coarse particles (>10 mm and 5–10 mm) gradually decreases, while finer particle content increases toward the resurgence. The roundness of Carboniferous sediments remains relatively constant, although it is significantly influenced by the presence of well-rounded, weak and ductile slag clasts. Overall, both the slag content and the proportion of well-rounded and rounded clasts in the coarser fractions (>10 mm and 5–10 mm) show a decreasing trend toward the resurgence.

Patterns of benthic diversity in marine underwater caves of the Marseille Region (France, North-Western Mediterranean Sea)

Underwater caves are remarkable habitats of the Mediterranean Sea. In the present study, we compare the geomorphology of four underwater caves of the Marseille area and the associated sessile assemblages across two contrasted communities (Semi- Dark and Dark-cave communities). Using a non-destructive method of sampling, photoquadrats of the walls of the caves were performed in 2020 to assess the biodiversity and the structure of these communities. In addition, taking advantage of available reference data from 2015, we evaluate the changes in sponge assemblages for the period 2015-2020, focusing on observations of the Semi-Dark cave community. Our results illustrate how the diversity of environmental settings and cave morphologies shape the benthic community composition of the four caves. In all four caves, the Semi-Dark community is the more diverse and harbours the higher number of species when compared to the Dark community. Each cave presents a different species assemblage with in most cases, distinct dominant species which highlight the singularity of each cave. Moreover, our temporal change assessment demonstrates a critical decrease in sponge species richness for all caves, possibly related to the increasing frequency of marine heatwaves that have occurred in the last decade. Although some species (mostly in the Keratosa subclass) seem to be particularly affected, other species such as Chondrosia reniformis appear to have benefitted from the situation. Our findings underline the importance of biodiversity monitoring in a context of a rapidly changing environment, in particular in poorly resilient marine ecosystems such as underwater caves.

Environmental and Human Impact on Ice Caves: The Example of the Wielka Śnieżna Cave in the Tatra Mountains (Poland)

Ice caves are characterised by specific microclimate, defined by the external climate as well as cave morphology (hence the location). They are unique components of Earth’s heritage. The ice formed there holds important paleoclimatic information and can be used to assess the global warming effect on the cryosphere in non-glaciated areas. We present an example from Wielka Śnieżna, the deepest cave system in the Polish Tatra Mountains, located in Tatra National Park (Tatrzański Park Narodowy). There have been no recent studies completed on the topic in this location. We provide the first contemporary results of temperature measurements by analysing microclimatic patterns and their response to global warming. There is ongoing ablation of the Ice Fall located in one of the lower entrances (Śnieżna) showing that the ice level has decreased by around 2 m in the last 10 years. The cave is under a minor human impact as it can be accessed only by professional cavers. However, some practices impact the balance of this fragile environment. By comparing our results with the outside temperature records, we aim to understand how dependent the cave microclimate is on the external fluctuations and changes. The ice in the Śnieżna is expected to be gone in the current century.

Hypogenic caves of Syracuse area, Sicily (Italy): geomorphological evidence of CO2 degassing, fresh-salt water mixing, and late condensation corrosion

Many caves in Sicily have been shown to have a sulfuric acid or other hypogenic origin. We studied three caves (Palombara, Scrivilleri, Monello) near Syracuse (eastern Sicily), in an area that was strongly uplifted and faulted, creating multiple Pleistocene marine terraces. Mineralogy, stable isotopes and dating methods (paleomagnetism, U/Th) were used to characterize cave sediments, some of which were related to the initial hypogenic phase (Fe and Mn oxides, calcite spar), others were introduced by surface runoff later. Many other sediments are the result of in situ weathering, such as lime sands produced by condensation-corrosion processes on the calcarenite walls. Phosphates, kaolinite and montmorillonite are related to bat guano decay. Stable isotopes show that the speleothems derive from surface seepage with temperatures similar to the present, with no evidence of a hydrothermal origin. Other deep sources of aggressivity are also excluded. We obtained an age of 603 ka for a marine notch deposit near Palombara, as well as a possible paleomagnetic inversion (>780 ka) for clastic allogenic sediments. These ages are discussed, raising the question of the reliability of calculations extrapolated from marine terrace dating and the possibility that the caves may be older than expected. Cave morphologies clearly indicate a hypogenic phase, with aggressive ascending flows creating the typical Morphologic Suites of Rising Flow (MSRF). The bubble trails and acid notches are formed by carbonic degassing and subsequent acidification in more or less closed aerated environments at the water table. Carbon dioxide probably derived from both the bedrock and the oxidation of surface-derived organic carbon at the density boundaries of the freshwater lens. We propose a mixed Flank Margin Cave and hypogenic speleogenesis model, where dissolution was favored in areas of greater CO2 concentration, producing phreatic maze patterns recording past sea-level positions. We suggest that aggressiveness of the rising fluids could have partly originated at a shallow depth, in the mixing zone between fresh and salt water.

Charlotte: A modern tool for cave surveying

The future of cave surveying is a full 3D scan, as automatic as possible, capturing all morphologically relevant details. However, the vast majority of cavers are still using tools designed more than 15 years ago. The advancements in tools for architects, CAD designers, programmers of VR and robotics could be helpful also for the caving community. That’s why Charlotte, a cheap DIY 2.5D scanner designed for cave surveying, was developed and built. To demonstrate its capabilities, a new survey of Grotta Regina del Carso cave (cad. nr. 2328/4760VG), the biggest cave in the Gorizia Karst, has been realized and published. The new scanner is based on the same traditional cave surveying techniques, familiar to all cavers, and features a LiDAR to capture the exact cave morphology. The results are so realistic they can be used for 3D animations, physics simulations, or even 3D printing. The prototype of the new tool costs less than 400€ (EURO; as of December 2022). All the source code and schematics are released as Free and Open Source. Cavers are encouraged to fork the project on Github and provide new functionalities, to keep up with new technology available and the needs of caving scientific research all around the world.

Mechanism, mode, and prediction of karst caves collapse in the deep marine carbonate fracture-cavity reservoir

Tahe oilfield in the Tarim Basin of China is a typical deep marine carbonate fracture-cavity type reservoir. Large paleokarst caves are the important storage space types in this reservoir. Drilling data reveals that most of the caves have varying degrees of collapsed breccia filling. A better understanding of cave collapse mechanism, modes, and distribution is crucial for highly efficient production. In this study, large karst caves in the Ordovician of Tahe oilfield are taken as research objects, and several types of typical cave conceptual models are established based on similarity theory. Physical tests and numerical simulation methods are used to reveal the collapse mechanism under different depths, shapes, filling types, and tectonic stresses of different periods. Collapse modes are established based on the revealed mechanism, morphology, and damage zone of simulated karst caves. Seismic prediction methods of different types of collapsing caves are explored according to their reflection characteristics. The results reveal that compaction and shearing damage are the main reasons for cave collapsing. The roof and surrounding rock of the cave sink in during the collapse process, with a shear-slip damage zone of 2–3 times larger than the cave diameter. The sand/mud-filled cave is shown to be more stable than the water-filled cave, and the unfilled cave is the least stable. Tectonic stresses acting in the early Hercynian period are the primary reason for the current collapsed caves. Two cave collapse modes are established, type Ⅰ being mainly affected by overlying gravity and type Ⅱ mainly affected by shear stress. There are local differences in seismic reflection characteristics between these two types. The prediction of the two types of collapsed karst caves can be realized by combining the seismic attribute of colored inversion, frequency division energy, GR inversion and coherent energy gradient, etc. The comprehensive prediction results of collapsed karst caves in Tahe oilfield show a good correspondence with oil well productivity.

A Multimodal Approach to Rapidly Documenting and Visualizing Archaeological Caves in Quintana Roo, Mexico

Abstract. Clearing and construction activities related to the Maya Train (Tren Maya) project resulted in potential and inevitable impacts to archaeological caves sites in largely undeveloped areas of Quintana Roo. An effort coordinated by Mexico’s National Institute of Anthropology and History (INAH) involved accelerated digital documentation of two caves – via SLAM-enabled mobile LiDAR scanning and targeted photogrammetry – to facilitate prompt visualization and evaluation of terrestrial and subterranean geospatial relationships. Mobile LiDAR is well suited to the challenges of capturing the complex, multilevel morphology of caves and was readily deployed across and through priority environments. Specific archaeological features – such as ancient Maya rock art and masonry shrines – were documented via photogrammetry, and the resulting higher-resolution models co-referenced with the georeferenced mobile LiDAR-generated point clouds of each cave and the surrounding topographic context. This integrative approach contributed to a more informed decision-making process, with respect to conservation and construction, and provided baseline data for future monitoring of the affected cave sites.

Influence of the last (de)glaciation on a complex cave system: Grønli-Seter cave system, Northern Norway

Cave studies enable us to unravel valuable information on landscape evolution. In glacial settings, the glacial cycles induced fluctuations in the underground hydraulic regime, sediment availability and base level in adjacent caves. Here, we present our work on the Grønli-Seter cave system in Northern Norway, which comprises >8 km of passage length at an elevation between 250 m and present sea level. By linking cave morphology and deposits to shifting glacier configurations and external base level changes during the last deglaciation and the Early Holocene, we establish how the hydraulic conditions in the cave system shifted in pace with glacier fluctuations. Maze sections and phreatic loops appear in a hydraulic confined setting close to the interface between the calcite marble and the overlying mica schist. Scallops in the cave walls demonstrate slow, ascending water flow, evidence of subglacial speleogenesis under wet-based, topographically constrained glaciers with a gentle surface slope. Moreover, cave morphology and clastic deposits indicate various hydrological phases of descending water flow, stagnant conditions, and excessive flow rates. Our work establishes that the last glaciation and deglaciation had an insignificant effect on the cave system's solutional development. In contrast, the cave sediments reveal diverse hydraulic conditions that may be related to shifting glacier configurations. This research offers valuable insights into glacier ice-contact speleogenesis and landscape development in glacial terrains.

The application of cave morphological and sedimentary deposit investigations to unravel tectonic history and landscape evolution: Insights from Veternica Cave, Medvednica Mountain, Croatia

Studies of cave morphologies and cave sediments may provide unique insight into landscape evolution throughout geological history. Here we present a study from Veternica Cave located within the isolated karst area of Medvednica Mt. in the northern part of Croatia, a tectonically active region that recently experienced several strong earthquakes. Cave morphology together with paleomagnetic dating of the cave clastic sediments and U-Th dating of speleothems were evaluated and correlated to the present-day topography and features of the active tectonics of the area. Sediment dating provides a temporal context for the paleohydrologic history of this system, which is proven to cover >600 ky, and probably a much longer period. Several phases of speleogenesis were identified and attributed to changing intensity of regional tectonic movements during the Pleistocene to the present day. A maximum rate of water table drawdown of 6 m/10 ky was calculated, which is comparable to the rates determined in other caves in tectonically active and/or glaciated regions. Additionally, our study reveals new evidence for unsteady dynamics of cave evolution characterized by an interchange of long stable periods with periods of rapid adjustments of the cave morphology as a result of tectonic uplift and base level lowering.

Morphometric Analyses of Greek Caves: How Morphology Predicts Cave Origin

Two of the most well-known caves of northern Greece, Petralona and Maaras, were morphometrically analyzed. They were strategically chosen for this morphometric study because they represent caves formed by different speleogenetic factors, resulting in patterns that clearly discriminate them from each other. Caves can display substantial variation in their patterns, depending on the local geology, hydrogeology, tectonics, and other factors. These qualitative parameters of speleogenesis, such as geological and hydrogeological controls, can be reflected in a cave’s pattern. The different speleogenetic factors that create the patterns of the caves can be expressed in the mathematical indices, designating them as morphometrical tools for properly discriminating the two cave patterns. Petralona Cave falls into the category of a ramiform cave pattern. The cave’s hypogenic origin is also supported by meso-scale cave morphology, and the hydrothermal activity of the surrounding area. On the other hand, Maaras Cave has a typical underground river pattern. The horizontal patterns of the two caves were morphometrically scrutinized using Euclidean and fractal geometry.

Contribution of Lasergrammetry, Photogrammetry and Electrical Tomography for the Survey and 3D Representation of Caves: Case Study of the Cave of Kef El Baroud, Province of Benslimane, Morocco

The modeling of caves is constantly evolving and the classic modeling tools are giving way to new techniques that are more precise and more practical, indeed scientists are increasingly using 3D modeling to improve the representations of caves, in this study we have used lasergrammetry and photogrammetry which occupy an increasing place in the 3D representation of caves. Their simplicity favors their use for recording and modeling the parietal morphology of caves and the detailed representation of the complexity of Endokarst. As part of the geomorphological study of the Kef El Baroud Cave which is located in the province of Benslimane in Morocco, two modeling methods were carried out, it is a digital survey by lasergrammetry and by photogrammetry of the cave. and its parietal morphologies. The study was completed by a topographical survey with a DistoX rangefinder. The geophysical contribution by electrical tomography was also carried out. The 3D terrestrial laser scanning technique was performed by a LEICA RTC 345 scanner. These measurements made it possible to reconstruct the evolutionary stages of the paragenetic morphologies, and their relationships with the local geomorphology, and the structural elements. The field measurements were integrated into the morphometric analyzes of the digital models, which allowed a large number of observations.The surveys also made it possible to compare the results with those of the photogrammetry carried out by a reflex camera and a wide-angle lens with appropriate editing software.Lasergrammetry and its application have enabled us to precisely position within the point cloud all the details of the covered wall, and thus constitutes, alongside photogrammetry, an interesting means for the geomorphological study of the Caves. An electrical tomography study was coupled with the other measurements and made it possible not only to delimit the walls of the Cave according to the resistivity gradients but also to detect the very probable presence of fractured zones under the Cave which could constitute an aquifer.

Preliminary data of potentially hazardous radon concentrations in Modrič Cave (Croatia)

Instigated by relatively high cave-air CO2 concentrations in Modrič Cave (Croatia) recorded for the purpose of speleothem-based paleoclimate research, we established preliminary monitoring of radon (222Rn) concentrations within the cave for a 4.5-year period (2018–2022). As radioactive geogenic gas, radon, which often correlates with cave-air CO2 concentrations, presents a potential health hazard in cases of longer exposure time in high concentration conditions. Since the Modrič Cave is open to tourists and long-term scientific research has been performed within, a safety assessment for radon concentrations was essential. The integrated measurements of radon concentrations were performed by passive LR115 detectors that were exposed from three to six months at eight sites within the cave. Preliminary results showed seasonal variations of radon concentrations (0.08–13.6 kBq/m3) governed by the cave ventilation patterns, but superimposed on this, cave morphology and bedrock architecture control the radon variations on finer spatial scale. The 3-months average 222Rn concentration of up to 13.6 kBq/m3 during summer in one of the cave passages is among the highest measured seasonal averaged radon concentrations in Croatian caves, but maximum concentrations were even higher. Based on obtained results and calculations, potential negative health effects of radon exposure for cave visitors, guides and scientists were assessed and the results showed values of exposure to be below recommended levels. Calculated worst-case scenario for cave guides (most affected by radon and its progeny) revealed that they would receive dose slightly below the occupational dose limit of 20 mSv/y (19.0 ± 5.2 mSv/y) in the touristic part of the cave and significantly higher doses (34.1 ± 9.2 mSv/y) in the non-touristic part of the cave. To detect precise spatio-temporal radon concentration variations (up to diurnal scale) we recently established continuous radon measurements. This will enable detection of possibly health threatening short-term peaks in radon concentration and consequently further improve cave management.

Does size matter? Bat diversity and the use of rock shelters in Brazil

A positive correlation between cave size and bat diversity has been recorded by some authors for different cave areas in South America. We analyzed published and otherwise available data from three Brazilian karst areas and phytogeography domains, including NE and SE Atlantic Forest and Cerrado (savannah-like vegetation), encompassing a wide range of cave sizes. We found no such correlation, as expected in view of previous observations by researchers and speleologists. We discuss the ecological implications of different ways to measure bat diversity, i.e. the accumulative number of species (sequential use of caves) vs. the number of species at a given occasion (species in actual cohabitation) vs. bat abundance (numbers of individuals), as well as speleological topics related to the concept of caves (based on an anthropomorphic definition, not applicable to other species), the problems of estimating topographic variables such as cave area and volume, and the value of including cave temperatures in the analyses. Multiple interacting variables may influence the composition of cave bat communities and bat species richness and abundance. The most important ones would be the density of caves in a given area (related to lithology – calcareous vs. siliciclastic caves), regional climates, and degree of preservation of epigean habitat. Cave morphology, number and size of entrances, and presence of water bodies, as well as interactions with other species, must also be considered. In conclusion, as a general statement for tropical and subtropical bats, cave size (in the human sense) by itself does not matter, except perhaps for one-off situations. Finally, a brief overview of the diversity of cave bats in Brazil is presented.

Spatiotemporal Variation Characteristics and Influencing Factors of Karst Cave Microclimate Environments: A Case Study in Shuanghe Cave, Guizhou Province, China

To systematically analyze the spatiotemporal heterogeneity, diurnal variation characteristics, and influencing factors of karst cave microclimate environments in Mahuang Cave, a cave in the Shuanghe Cave National Geological Park in Guizhou Province, China, was investigated. Monthly monitoring of meteorological and environmental parameters, such as wind speed, air pressure, humidity, and temperature indicators inside the cave and atmospheric temperature and precipitation outside the cave, was conducted from 2019 to 2021, as well as encrypted monitoring in August and December 2019. The results showed that: (1) The meteorological parameters of Mahuang Cave exhibited seasonal characteristics and cyclical interannual variation. Cave wind speed, relative humidity, and temperature were high in summer and autumn and lowest in winter, whereas cave air pressure was high in winter and low in summer. The atmospheric temperature outside the cave was the main controlling factor. (2) On a short time scale, the dewpoint and temperature of Mahuang Cave did not change significantly, and an abrupt change phenomenon occurred mostly around noon. The warm season was more sensitive than the cold season, and the closer to the entrance of the cave, the stronger the response. (3) In terms of spatial distribution, the overall microclimate factors of Mahuang Cave became increasingly stable and entered a constant state with the increasing depth of the cave passage. The related effects of cave morphology and structure, the physical environment of the cave passage, air movement, and groundwater dynamics were important factors leading to an abrupt change phenomenon in cave microclimates. Local meteorological conditions and cave geometry controlled the temporal variability and spatial heterogeneity of the cave microclimate environment.

Study on Sustainable Development of Carbonate Reservoir Based on 3D Printing Technology

With its abundant reserves in the world, carbonate reservoir has become one of the main targets for future oil and gas development. Accelerating the research and development of carbonate reservoirs is thus significant to enhance the world’s energy supply capacity. However, there have been some problems in the evaluation of carbonate reservoirs for a long time, such as low description accuracy of fractured-vuggy bodies, diverse flow patterns, and difficult reservoir simulation and prediction. Compared with traditional manufacturing methods, 3D printing is an advanced manufacturing technology of rapid prototyping. It has the characteristics of short manufacturing cycle, not limited by the complexity of parts, material saving and energy saving, and thus has unparalleled advantages in reservoir rock analysis. In this paper, the carbonate core of Yingmaili region in Tarim Basin was taken as the research object, and the uniaxial compression mechanical properties of three small cores printed with different materials were designed and tested by using KINGS-600 3D photocuring printer and photosensitive resin materials. After that, UV-9400S white resin with the highest strength is selected as the printing material of the full diameter core model of the karst cave. Combined with the CT scanning of the formed samples, the control accuracy concerning the cave morphology of the 3D printed samples was tested which adequately proves that flow experiments can be carried out with 3D printed core samples. At last, the article also analyzes the shortcomings of 3D printing technology, and points out the direction for its large-scale application in the field of oil and gas exploitation. This study can especially provide a reference for the application of 3D printing technology in the field of carbonate reservoir development, and ultimately promote the sustainable supply of oil and gas resources.

Airflow dynamics in Wind Cave and Jewel Cave: How do barometric caves breathe?

Recent research on air pressure propagation through barometric caves has revealed various speleoclimatological processes, which cause a more complex relationship between surface air pressure changes and resulting pressure gradients between cave and surface air than previously assumed. So far, however, studies on barometric cave airflow have only been based on surface air pressure measurements. Thus, this study investigates and compares airflow at the openings of Wind Cave and Jewel Cave – two major barometric cave systems in South Dakota, USA – as a response to surface air pressure changes and air pressure gradients. Based on high-resolution long-term air pressure measurements from the surfaces and several locations inside the caves, as well as ultra-sonic airflow measurements at the openings, the analysis proves that for both caves, cave airflow velocity can be predicted more accurately by air pressure gradients than by previous surface air pressure changes. An inter-cave comparison also reveals substantial differences in cave airflow dynamics between Wind Cave and Jewel Cave, with the relevant period of surface air pressure variations for cave airflow velocity and the cave reaction times being significantly longer at Jewel Cave compared to Wind Cave. Therefore, the findings of this study demonstrate the effects of cave morphology on airflow and significantly contribute to a better understanding of the speleoclimatological mechanisms and dynamics of compensating airflow at the openings of barometric caves.