Cave Entrance Research Articles

In the land of the blind: Exceptional subterranean speciation of cryptic troglobitic spiders of the genus Tegenaria (Araneae: Agelenidae) in Israel

Caves have long been recognized as a window into the mechanisms of diversification and convergent evolution, due to the unique conditions of isolation and life in the dark. These lead to adaptations and reduce dispersal and gene flow, resulting in high levels of speciation and endemism. The Israeli cave arachnofauna remains poorly known, but likely represents a rich assemblage. In a recent survey, we found troglophilic funnel-web spiders of the genus Tegenaria in 26 caves, present mostly at the cave entrance ecological zone. In addition, we identified at least 14 caves inhabited by troglobitic Tegenaria, which are present mostly in the twilight and dark ecological zones. Ten of the caves, located in the north and center of Israel, are inhabited by both troglophilic and troglobitic Tegenaria. These spiders bear superficial phenotypic similarities but differ in the levels of eye reduction and pigmentation. To test whether these taxa constitute separate species, as well as understand their relationships to epigean counterparts, we conducted a broad geographic sampling of cave-dwelling Tegenaria in Israel and Palestine, using morphological and molecular evidence. Counterintuitively, our results show that the troglobitic Tegenaria we studied are distantly related to the troglophilic Tegenaria found at each of the cave entrances we sampled. Moreover, seven new troglobitic species can be identified based on genetic differences, eye reduction level, and features of the female and male genitalia. Our COI analysis suggest that the Israeli troglobitic Tegenaria species are more closely related to eastern-Mediterranean congeners than to the local sympatric troglophile Tegenaria species, suggesting a complex biogeographic history.

Phylogeny of Saxifraga section Saxifraga subsection Arachnoideae (Saxifragaceae) and the origin of low elevation shade-dwelling species.

Saxifraga section Saxifraga subsection Arachnoideae is a lineage of 12 species distributed mainly in the European Alps. It is unusual in terms of ecological diversification by containing both high elevation species from exposed alpine habitats and low elevation species from shady habitats such as overhanging rocks and cave entrances. Our aims are to explore which of these habitat types is ancestral, and to identify the possible drivers of this remarkable ecological diversification. Using a Hybseq DNA-sequencing approach and a complete species sample we reconstructed and dated the phylogeny of subsection Arachnoideae. Using Landolt indicator values, this phylogenetic tree was used for the reconstruction of the evolution of temperature, light and soil pH requirements in this lineage. Diversification of subsection Arachnoideae started in the late Pliocene and continued through the Pleistocene. Both diversification among and within clades was largely allopatric, and species from shady habitats with low light requirements are distributed in well-known refugia. We hypothesize that low light requirements evolved when species persisting in cold-stage refugia were forced into marginal habitats by more competitive warm-stage vegetation. While we do not claim that such competition resulted in speciation, it very likely resulted in adaptive evolution.

Assessment of microbial communities colonizing the Azé prehistoric cave

• Biofilms were assessed inside and outside the Azé prehistorical cave. • Several vestiges remain in the cavity and are colonized by microorganisms. • Each section of the cave host different bacterial or phototrophic communities. • The microbial richness decreases from the outside to the bottom of the cave. • The outside environment is the main driver of the cave communities. This present study addresses the question of the composition of both prokaryotic and eukaryotic microbial communities outside, at the entrance and inside the prehistoric Azé cave using a metabarcoding survey. The results showed that cave bacteria as well as Eukaryote phototrophs richness were negatively correlated with the distance from the cave entrance. In fact, outside the cave, richness, diversity and specific OTUs were significantly higher in comparison to the entrance and the bottom of the cave. Moreover, this study reported that each section of the cave host different communities. The differences in communities provide a better understanding of the microorganism sources in the Azé show cave.

3D data integration for geo-located cave mapping based on unmanned aerial vehicle and terrestrial laser scanner data

The Akçakale cave is a significant natural and cultural heritage site in the Black Sea region of eastern Turkey. The complex geometry and difficult-to-access areas of the cave have made the use of traditional mapping methods challenging. To overcome these limitations, this study utilized TLS and UAV technology to produce highly accurate 2D and 3D data for cave management and risk assessment purposes. The TLS system was used to create a detailed 3D point cloud of the cave interior, while the UAV system generated a 3D model of the surface topography outside the cave. The two sets of data were combined in the GIS environment using a geodetic network established in the study area, providing a common geodetic reference system for both TLS and UAV data. The study found that the cave area is 13,750 m2, which is smaller than the area of 18,000 m2 that was previously estimated using conventional measurement methods. The volume and ceiling heights of the cave were calculated using the elevation models generated from TLS point cloud data. The 3D point cloud data were also used to map dripstone locations on the floor and ceiling of the cave, and the boundaries of rock blocks on the ground were precisely determined. The study identified potential risks associated with the cave, particularly the risk of rockfall in the source rock areas around the cave entrance and the southern part of the cave. The nearest building to the cave is approximately 35 meters away, and all the buildings in the area are less than 300 meters from the cave. In the event of the cave collapse, the buildings in the southern part of the cave are at risk of rockfall. This study demonstrates the effectiveness of combining data from TLS and UAV systems to generate broad and sensitive cave mapping and risk assessment data, which are critical for cave management and safety. The collected data can be used for cave stability investigations and rockfall risk assessments. This study provides a foundation for future explorations of the Akcakale cave and highlights the potential for modern surveying techniques to enhance our understanding of complex geological structures such as caves.

Soil loss through fissures and its responses to rainfall based on drip water monitoring in karst caves

Owing to the binary geologic structure, soil loss in the karst region is characterized as a combination of surface erosion and underground soil loss. However, we know little about the process and amount of underground soil loss by now due to the difficulty in observation and identification. To predict soil loss accurately and control rocky desertification effectively, it is urgent to collect data of underground soil loss directly by new ways. In this study, 137Cs tracer technique, high frequency online monitoring and UAV survey were used to investigate soil loss through fissures. The soil samples were collected in five karst caves of Guizhou Province for determining 137Cs activity. In two of these caves, the improved monitoring devices were adopted to monitor drip water online, and the sediment content in drip water was measured once a month. Furthermore, depending on 5 exposed karst sections, the distribution density of fissures was surveyed with UAV to calculate the average underground soil loss modulus in the watershed. The results showed that (1) the soil materials deposited in caves were mainly transported by runoff from the cave entrance, rather than through fissures above the caves. (2) The initial response time and duration of drip water in caves to rainfall were controlled by surface land coverage and the process of precipitation. And the variation of sediment content in drip water kept almost constant with rainfall except at the beginning of the rainy season. (3) The directly measured underground soil loss rate monitored through the fissure above a cave with high bedrock exposure rate and a cave with high vegetation coverage was 2.42 g·yr−1 and 0.36 g·yr−1, respectively. (4) The average underground soil loss modulus in the area with high bedrock exposure rate and with high vegetation coverage was 0.35 t·km−2·yr−1 and 0.05 t·km−2·yr−1, respectively. This study is helpful for understanding the process and intensity of underground soil loss.

Late Pleistocene and Holocene malacological and theriological faunas from the Tetyukhinskaya Cave (southern Far East, Russia) and their palaeoecological implications

Assemblages of terrestrial molluscs and small vertebrates were recovered from the Tetyukhinskaya Cave, located in the vicinity of the Dalnegorsk city, Primorsky Krai (south of the Far East, Russia), from which we identified characteristic zones of molluscs and small mammals. Based on analysis of the malacofauna and theriofauna, we interpret the molluscs as indicators of the biotopes at the cave entrance, and the mammals as indicators of the cave surroundings, and during late Late Pleistocene and Holocene, forests existed near the area surrounding the cave. The small mammal fauna suggests the development of open spaces of a pasture-like ecosystem during the warm periods of the Late Pleistocene with the development of the forest vegetation. This study demonstrates the importance of complex faunal investigations for the reconstruction of the palaeoenvironment in the Late Pleistocene and Holocene.

Investigation of the Characteristic Nighttime Temperature of Potential Caves on Mars

By providing an environment where energetic particles and micrometeorites can not penetrate, caves on Mars may serve as a human shelter in future Mars explorations. More than 1,000 cave entrance candidates have been detected; however, their physical characteristics that can be utilized in detecting more candidates have not been explored in detail. In this paper, we explore the nighttime temperature of 100 cave entrance candidates and their surrounding areas to investigate 1) the nighttime temperature tendencies relative to their surrounding areas and 2) the extent of these temperature differences. We find that 79% of the cave entrance candidates exhibit higher temperatures than the surrounding areas, and 59% show a temperature difference over 20K, suggesting that the cave entrances may generally show higher temperatures than the surrounding areas during the nighttime.

Multi-spatial analysis on cave ecosystems to predict the diversity of subterranean invertebrates

Subterranean habitats around the world can shelter diversified and threatened faunal communities. However, issues related to alterations in the landscape and structure of subterranean habitats still need to be better understood. Therefore, we used a multi-spatial scale analysis of land cover, land use, and cave habitats to predict the diversity of communities of subterranean invertebrates. We hypothesized that changes in land cover promote alterations in both faunal richness and composition and microhabitat diversity and that microhabitat features determined subterranean biodiversity. Sixteen limestone caves were sampled in Brazil at micro, meso, and macro scales using quadrats (1m²), transects (100 meters) as sample units inside caves and buffers with the radius of 100 and 250 meters in the surroundings of the cave entrances. Models performed showed that land cover and land use influenced cave environments, regarding both microhabitats traits and terrestrial invertebrate richness and composition. We also observed a relationship between microhabitat structure and terrestrial invertebrate richness and composition. Our results showed that deforested areas had negative effects on species richness and changed their composition, while natural areas had positive effects on microhabitat diversity. The same effects were observed for both 100 and 250 meters buffers. Invertebrate richness was negatively predicted by deforested areas while positively predicted by natural areas. Richness was also positively predicted by the combination of all microhabitat traits, and dissimilarity of fauna was influenced by microhabitat diversity in mesoscale and microscale by all microhabitat elements. The results highlight the importance of the landscape surrounding the caves to conserve the subterranean habitats and their fauna. Due to the spatial and temporal changes in the global environmental scenario, we argue the urgency of further detailed studies in fragmented landscapes to define minimum areas of protection for cave environments.

A micro-geoarchaeological view on stratigraphy and site formation processes in the Middle, Upper and Epi-Paleolithic layers of Sefunim Cave, Mt. Carmel, Israel

This paper presents a micro-geoarchaeological study carried out on the sedimentary sequence exposed at the entrance of Sefunim Cave, Israel, a sequence that spans from the Middle Paleolithic to the early Epipaleolithic periods. Using FTIR and micromorphological techniques, we investigated the stratigraphic sequence to reconstruct patterns of site use and archaeological formation processes. We identified formation processes that are common among Paleolithic caves sites in the Southern Levant, mainly the deposition of local terra rossa through colluvial sedimentation. Taphonomic disturbances of the deposits range from minimal to moderate, exhibited mainly by root and burrowing activity, but with no evidence for significant transport of archaeological materials. While the upper layers (II–III) are decalcified, the precipitation of secondary calcite results in increasing cementation of the sediments with depth in the lower layers (V–VII). We observed variation at the microscopic scale and identified an inverse correlation between human and carnivore activity throughout the layers. We observed human activity by the presence of micro-archaeological materials such as chert, bone, charcoal, rubified clay, burnt bone and shell, and wood ash. We observed carnivore activity by the presence of phosphatic grains and coprolite fragments as well as chewed and digested bones. We conclude that human activity at the site was characterized by episodes of varying intensity, based on the frequency of archaeological finds within the different layers. The alternating episodes of human and carnivore activity at Sefunim Cave may demonstrate the close-knit interactions and reciprocal relations that humans and carnivore shared at Paleolithic caves.

Life post-death: Colonization of a bat carcass by Microcerella halli (Engel, 1931) (Diptera: Sarcophagidae) in a Neotropical cave

Caves are habitats characterized by low light or total darkness, whose fauna is largely composed of animals that adapt to dark environments, such as bats and many arthropods. Here, we present the first record of bat carcass colonization by Diptera larvae in a cave in the Neotropics. Twenty-one adult specimens of Microcerella halli (Sarcophagidae), seven males and 14 females, emerged from larvae collected in a carcass of Pteronotus gymnonotus (Mormoopidae) found in a twilight zone, about 15 m from the cave entrance. The mean time between carcass collection and adult emergence was 17.99 ± 0.44 days. As colonization by M. halli only occurs after death, we estimated the mean duration of the pupal stage – by recording daily pupation and emergence data – and attempted a preliminary estimate of the post-mortem interval, which indicated that larviposition occurred at least 24 h before carcass collection. Furthermore, we discussed the fact that M. halli females can find and colonize carcasses in low light environments, reinforcing the forensic potential of the species.

Algae and cyanobacteria in the aphotic habitats of Veternica Cave (Medvednica Mt., Croatia) and selected caves of the Dinaric karst (South-Eastern Europe)

Microphototrophs (algae and cyanobacteria) in karst environments have been intensively studied in aquatic epigean habitats. In recent decades knowledge about the communities inhabiting cave entrances and lampenflora has grown substantially, but the data about the communities in aphotic cave zone are scarce. This study aimed to investigate spatio-temporal presence of microphototrophs in the aphotic zone of Veternica Cave (Mt. Medvednica karst) and to present additional preliminary data from 22 caves of the Dinaric karst. The data were collected over ten years, in parallel with research on cave phagotrophic protists. In addition to the remains of microphototrophs, living algae and cyanobacteria were found in the cave aphotic zone. Diatoms (Bacillariophyta) were the most frequent group found, followed by green algae (Chlorophyta), golden-brown algae (Chrysophyta) and the filamentous cyanobacteria (Cyanobacteria). The presence of microphototrophs was detected throughout the year but showed spatio-temporal variations. Microphototrophs were absent in the parts of Veternica Cave with seeping and dripping water, while they were occasionally present in the hydrologically active parts of the cave. The presence of diatoms in the aphotic zone of Veternica Cave was related to hydrological conditions, and was not affected by the distance from the cave entrance. The presence of microphototrophs in caves of the Dinaric karst has been associated with caves subject to various types of flooding by endogenous and exogenous water. Despite the fact that microphototrophs are passively transported to the caves from the surface habitats, the presence of live individuals in the cave aphotic zone implies that they should not be neglected in discussions about cave food webs. Future research of microphototrophs should be focused on the species identification, their abundance, survival time, and detail description of conditions that determine their presence in caves.

Plausible Detection of Feasible Cave Networks Beneath Impact Melt Pits on the Moon Using the Grail Mission

In the future, when humans build their bases on terrestrial planets and their moons, caves will be the safest place for inhabitation. Large holes, believed to be cave entrances, have been discovered on the Moon, along with small features called “impact melt pits.” In the Gravity Recovery and Interior Laboratory (GRAIL) gravity model, which is expressed in spherical harmonics (SH), it is difficult to express the gravity anomaly created by a small empty space below the surface. Nevertheless, we propose that a cave network, akin to an anthill, exists under the impact melt pits discovered on the Moon. This is because we think it is natural to apply a network created by Earth’s small caves to the Moon. We obtained accurate Bouguer gravity measurements by calculating regional crustal density using localized admittance of the study area and detected weak gravity (mass deficit) information. By increasing the degrees and order of SH at regular intervals, we estimated the change in gravity at a specific position at high degrees and order, thereby extracting shallow depth information. To validate our method, we compared our results with those of existing studies that analyzed the previously known Marius Hills Hole (MHH) area. The analysis of seven regions in our study area revealed a mass deficit in some impact melt pits in four lunar regions (Copernicus, King, Stevinus, and Tycho). We propose that there is a cave network in this region, indicated by the gravitation reduction in the impact melt pits region. Our results can be useful for the selection of landing sites for future in situ explorations of lunar caves.

Niche differentiation of atmospheric methane-oxidizing bacteria and their community assembly in subsurface karst caves.

Karst caves are recently proposed as atmospheric methane sinks in terrestrial ecosystems. Despite of the detection of atmospheric methane-oxidizing bacteria (atmMOB) in caves, we still know little about their ecology and potential ability of methane oxidation in this ecosystem. To understand atmMOB ecology and their potential in methane consumption, we collected weathered rocks and sediments from three different caves in southwestern China. We determined the potential methane oxidization rates in the range of 1.25 ± 0.08 to 1.87 ± 0.41 ng CH4 g-1 DW h-1 , which are comparable to those reported in forest and grassland soils. Results showed that alkaline oligotrophic caves harbour high numbers of atmMOB, particularly upland soil cluster (USC), which significantly correlated with temperature, CH4 and CO2 concentrations. The absolute abundance of USCγ was higher than that of USCα. USCγ-OPS (open patch soil) and USCγ-SS (subsurface soil) dominated in most samples, whereas USCα-BFS (boreal forest soil) only predominated in the sediments near cave entrances, indicating niche differentiation of atmMOB in caves. Overwhelming dominance of homogenous selection in community assembly resulted in convergence of atmMOB communities. Collectively, our results demonstrated the niche differentiation of USC in subsurface alkaline caves and their non-negligible methane-oxidizing potential, providing brand-new knowledge about atmMOB ecology in subsurface biosphere.

Extended-range luminescence chronologies for the Middle Pleistocene units at the Sima del Elefante archaeological site (Sierra de Atapuerca, Burgos, Spain)

The Sima del Elefante site is located within the Sierra de Atapuerca karst system (Burgos, northern Spain), and forms part of a series of important Early, Middle and Late Pleistocene archaeological complexes that have been dated previously with luminescence techniques (Gran Dolina, Galería Complex, Sima de los Huesos, Galería de las Estatuas). This study focuses on the upper Middle Pleistocene units (TE18 and TE19) at Sima del Elefante, which contain Acheulean and transitional lithic assemblages (Mode 2/3), as well as large and small mammal fossils. Importantly, these uppermost units are associated with a sediment plug located in the cave's interior at Galería Baja, which marks the closure of a significant palaeoentrance to the Atapuerca karst system. Establishing the accumulation history of these related deposits is important for understanding both Lower Palaeolithic technological dynamics via comparisons with similar levels at other Atapuerca sites (i.e., Gran Dolina and Galería Complex), as well as past human occupation patterns and carnivore use of (and accessibility to) the caves. We present single-grain TT-OSL and multi-grain pIR-IR chronologies for the Sima del Elefante upper sequence and the Galería Baja sediment cone, as well as U-series dating results for a stalagmitic crust capping the combined clastic infill sequence. The paired luminescence ages for the upper occupation levels are in agreement with each other and reveal that the host deposits accumulated 576–481 ka for the TE18 stratified scree layers, 266–237 ka for TE19 and 206–250 ka for the Galería Baja upper cone section (weighted mean 2σ age ranges). A concordant U-series age of 202 ± 65 ka is obtained for the overlying stalagmitic crust at Galería Baja. The Sima del Elefante ages are consistent with those previously obtained using U-series and biochronology, confirming that there is an erosional unconformity and complex carbonate deposition phase associated with the upper layers of unit TE18 and that the original cave entrance likely closed by ∼200 ka. Chronological correlation with other Atapuerca sites reveals potential equivalence between TE18 and unit TD8 (at Gran Dolina), and between TE19 and units GIIb–GIIIb (at Galería Complex) and, possibly, TD10.1 and TD10.2 (at Gran Dolina), though more refined dating is required to confirm the latter.

Study of the Diffusion Law of Harmful Gases in Tunnel Construction on Plateaus and Optimization of Ventilation Parameters.

To explore the diffusion law of harmful gases near the excavation face in tunnel construction on plateaus, select the optimal ventilation parameters, and improve the ventilation efficiency, Ansys Fluent was used to set the environmental parameters according to the highland, where the tunnel is located, and simulate and curve fit the diffusion phenomenon of CO and NO2 based on the fluid control equations and species transport model. The effects of air velocity, ventilation time, and duct position on the diffusion law of harmful gases were analyzed, from which the optimal ventilation conditions were selected, and the ventilation effects under the optimal conditions were compared with those under the original conditions. The study shows that after the fresh airflow passes through the outlet, part of it flows out along the tunnel wall toward the cave entrance, and the other part interacts with the return air to form a vortex; when the air supply speed is 10 m/s and the distance from the duct outlet to the excavation face is 25 m, the maximum concentration of harmful gases decreases by 92–99% after 20 min of ventilation compared with that before optimization and the smoke exhaust efficiency increases by 2.5% per minute.

Arthropod communities and drivers of their species diversity and composition in caves

Understanding the drivers of diversity patterns in ecological communities remains a major challenge in ecology. Moreover, few studies have considered invertebrate or subterranean communities and little is known about which factors are responsible for structuring arthropod communities in caves. In this study we: assessed the abundance, richness, and composition of arthropod communities from eight caves located in Banat and Mehedinti region, Romania; and determined whether altitude, cave physical characteristics (temperature, relative humidity, light intensity) and features (cave extension, hight, width, heterogeneity, substrate (wall versus floor)) influence cave arthropod communities along the horizontal development of the cave (i.e. from the cave entrance, through the intermediate zone, to the aphotic zone). assessed the abundance, richness, and composition of arthropod communities from eight caves located in Banat and Mehedinti region, Romania; and determined whether altitude, cave physical characteristics (temperature, relative humidity, light intensity) and features (cave extension, hight, width, heterogeneity, substrate (wall versus floor)) influence cave arthropod communities along the horizontal development of the cave (i.e. from the cave entrance, through the intermediate zone, to the aphotic zone). Overall, 89 species were found, of which three were obligate subterranean dwellers and 17 were endemic species. Species abundance distributions showed evident variation in species numbers among cave zones and between the wall and floor substrate. Species abundance was influenced by cave extension, relative humidity and light intensity. Species richness was related to cave extension while relative humidity and cave heterogeneity affected the species diversity. The results also indicated differences in species abundance, richness and diversity among cave zones and between substrate types. The arthropod community structure and composition was determined by altitude, relative humidity, temperature and substrate. The floor and wall substrate had different species composition while the species composition of the three cave zones largely overlapped. We conclude that several biotic and abiotic factors explain the diversity and composition of cave arthropods communities and that our results may be relevant to other types of island-like habitats.

New record and update on the geographic distribution of the Egyptian Tomb Bat Taphozous perforatus (E. Geoffroy, 1818) in Cameroon

The Egyptian Tomb Bat Taphozous perforatus is an emballonurid whose presence in Cameroon is least known. While there are previous records in the country from Waza and Yabassi, they are contested. Available publications fail to mention the presence of this species in the country, thus more information is needed to evaluate its presence. Recently, five specimens were captured near a cave entrance in Bocklé, Garoua in the Sahelian zone of northern Cameroon, adding a new locality to the distribution of the species. The discovery of this roost unequivocally confirms the presence of this species in Cameroon and indicates that the species has a wide distribution in the country as a resident species. Detailed geographical distribution of this species in Africa, along with detailed descriptions and photographs of available specimens are provided.

Detection and Classification of Potential Caves on the Flank of Elysium Mons, Mars

Martian caves have revived interest in the field of subsurface exploration because they are the potential destinations for future human habitats and astrobiological research. There are many pits on Mars, but some of them look like collapsed cave roofs. These special pits are formed by the collapse of surface materials into the subsurface void spaces. The signature of life is probable in a subsurface cave on Mars as the subsurface environment can protect life from the harsh and dangerous radiation environment of the surface. In a cave, there may be an abundance of minerals, fluids, and other key resources. Therefore, locating the access point of the subsurface cave is essential and crucial for formulating plans for robotic/human explorations of the Red Planet, Mars. We have used remote sensing data from Mars Reconnaissance Orbiter (MRO; NASA), Mars Global Surveyor (MGS; NASA), and Mars Odyssey (NASA) for identifying, mapping, and classifying selected special pit candidates on the flank of Elysium Mons, Mars. A total of 32 special pit candidates has been identified and classified based upon morphology and geological context. Out of these, 26 are newly discovered ones. The thermal behavior of 23 special pit candidates confirms that the special pits are radiating heat energy at nighttime, similar to potential caves. Also, cave entrances have been detected in nine candidates using data from the HiRISE camera onboard MRO. These sites could be important destinations for future robotic/human exploration and the search for life on Mars.

Microbial communities in carbonate precipitates from drip waters in Nerja Cave, Spain.

Research on cave microorganisms has mainly focused on the microbial communities thriving on speleothems, rocks and sediments; however, drip water bacteria and calcite precipitation has received less attention. In this study, microbial communities of carbonate precipitates from drip waters in Nerja, a show cave close to the sea in southeastern Spain, were investigated. We observed a pronounced difference in the bacterial composition of the precipitates, depending on the galleries and halls. The most abundant phylum in the precipitates of the halls close to the cave entrance was Proteobacteria, due to the low depth of this sector, the direct influence of a garden on the top soil and the infiltration of waters into the cave, as well as the abundance of members of the order Hyphomicrobiales, dispersing from plant roots, and other Betaproteobacteria and Gammaproteobacteria, common soil inhabitants. The influence of marine aerosols explained the presence of Marinobacter, Idiomarina, Thalassobaculum, Altererythrobacter and other bacteria due to the short distance from the cave to the sea. Nineteen out of forty six genera identified in the cave have been reported to precipitate carbonate and likely have a role in mineral deposition.

Examining sediment infill dynamics at Naracoorte cave megafauna sites using multiple luminescence dating signals

Relatively little is known about the long-term sediment accumulation dynamics of Naracoorte Cave Complex (NCC) solution pipe cavities, and many of the megafauna-bearing infill deposits at this globally significant Australian Pleistocene fossil locality remain partially dated or lack any numerical age control. In this study, we assess the suitability of three different luminescence dating signals for improving existing chronologies at six Late and Middle Pleistocene NCC sites (n = 22 samples), and we undertake multi-site examinations of NCC sediment infill dynamics spanning the last 550 thousand years (ka). Modern analogue samples collected from above and beneath two active cave entrances confirm that single-grain OSL, single-grain TT-OSL and multi-grain pIR-IRSL signals can be reset down to insignificant residual levels (<10−1–100 Gy) when compared with the natural dose ranges of interest for most NCC palaeontological applications. Replicate luminescence dating comparisons performed at six NCC fossil sites (n = 15 samples) reveal consistent ages for twenty-eight out of thirty-one paired OSL–TT-OSL, OSL–pIR-IRSL and TT-OSL–pIR-IRSL datasets. Nineteen of the twenty Middle to Late Pleistocene samples analysed from the NCC sites produce homogeneous OSL, TT-OSL and pIR-IRSL De datasets suggesting that the NCC solution pipe deposits considered here are generally not affected by syn-depositional mixing complications that can take place within closed karst cavities (i.e., the remobilisation of unbleached grains from pre-existing cave floor sediments, and their subsequent translocation and incorporation into deposits within deeper parts of the cavity along with externally bleached, allochthonous grain populations). Detailed examination of solution pipe dynamics at Smoke Tortoise Cave (SMT) reveals a complex accumulation history focused on the marine isotope stage (MIS) 9 and MIS 7 interglacial complexes, as well as the MIS 8e interstadial. The SMT case study highlights that NCC solution pipes are not simply associated with short-lived opening and sediment accumulation events, but may involve multiple, discontinuous deposition episodes and reactivation events. An initial multi-site examination of all published NCC infill chronologies (n = 70) appears to suggest statistically significant, preferential solution pipe development during the relatively wet parts of interglacial or interstadial cycles. The non-uniform infill age distribution implies that NCC solution pipe dynamics may have exerted taphonomic biases on fossil accumulation, which should be taken into consideration when reconstructing long-term palaeoecological histories from NCC solution pipe cavities.