Speleothems Research Articles

A Novel Protocol for Reconstructing Depositional Histories of Anthropogenic, Sedimentary Records: the Case of the Holocene-Deep Kirkhellaren Cave Deposits in Coastal Arctic Norway

ABSTRACT This paper presents a novel protocol for reconstructing formation processes of archaeological depositional sequences, applied to Holocene-wide cave deposits located on a remote coastal island in Arctic Norway as a case study. Extensive GPR surveying is correlated with geochemical analysis and in situ environmental deposit monitoring for sedimentary fingerprinting and forecasting of future preservation of organic remains. Subsurface deposit characteristics are integrated with a high-precision, laser-based 3D-reconstruction of the cave, enabling triangulation with historic photos and local informant knowledge that facilitate modeling and quantification of erosional history. The results showcase detrimental depletion of critical organic heritage, accelerated by the removal of protective surface layers after the a.d. 1930s. Critically, subsurface deposits are trending towards overshooting a threshold for accelerated in situ degradation. The results act as a direct validation of the methodology. Measures for future protection of similar archaeological deposits are discussed and an outline of the general applicability of the protocol.

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.

Discovery of a Pleistocene megafaunal assemblage in a cave in Sierra de El Abra, San Luis Potosí, Mexico

The Calera cave system in San Luis Potosí, Mexico, with a large Pleistocene megafaunal assemblage is described. Hundreds of fossil bones have been found throughout the 1324 m of mapped galleries. The fossils are well preserved resulting from partial permineralization by manganese oxide. A preliminary taxonomic identification of the recovered specimens indicates Equus sp. is the most abundant taxon. Other groups include mammoths, gomphotheres, cervids, bovids, camelids, sloths, glyptodonts, felids, canids, lagomorphs, and testudines. It has been estimated that the cave would have started to form between 1.17 and 0.29 Ma. Since the fossils are found on top of or form part of the fluvial sedimentary deposits inside the cave passages, fossil deposition is much younger and probably occurred during the latest stage of cave formation and the fauna represents a time-averaged accumulation. A few specimens are covered with secondary calcite incrustations. The locality described in this study stands out because it contains one of the largest Pleistocene megafaunal assemblages of the region.

Challenging underground geophysical, geological and topographical surveys in the Borna Maggiore di Pugnetto karst collapse cave to delineate its genesis and actual structure

AbstractElectric resistivity surveys in karst environments are commonly employed to establish parameters that can help in the evaluation of collapse risk related to sinkhole or cave formation. However, these surveys are often executed from the surface with consequent limits in resolution and identification potential as a function of coverage thicknesses. Application of these methodologies directly inside known caves, for a better understanding of their formation mechanisms, is uncommon due to accessibility problems, the nontrivial referencing issues that arise when operating in an underground environment and the challenging 2D/3D interpretation issues emerging from the presence of the cavity itself. This paper reports on the application of electric resistivity tomography along with specific geological and topographic mapping, inside the Borna Maggiore di Pugnetto karst collapse cave. Comprehensive knowledge of this cave, developed in mica‐rich and carbonate‐rich calcschists, is problematic with traditional investigations, due to the cave breakdown that masks its structure. In this study, the 3D geometry of the cave is reconstructed using a topographical survey. This reconstruction is then utilised to perform a 3D inversion of the electrical resistivity tomography (ERT) dataset. The results of both 2D and 3D inversions are compared and discussed, focusing on the survey's ability to identify resistivity anomalies within the 3D volume surrounding the cave. Additionally, an open‐source script is provided to facilitate the replication of this 3D modelling and inversion in similar underground contexts. Results of the paper show the effectiveness of the proposed surveys in the delineation of genesis and actual structure of the cave. The paper also proposes a methodological approach that can be adopted in similar contexts to enhance the understanding of speleogenesis.

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.

A biochronological date of 3.6 million years for "Little Foot" (StW 573, Australopithecus prometheus from Sterkfontein, South Africa).

A debate has developed with regard to geological ages of hominin fossils attributed to Australopithecus africanus and Australopithecus prometheus in South African Plio-Pleistocene cave deposits. For the Sterkfontein caves (Members 2 and 4), cosmogenic nuclide isochron (10Be/26Al) dating has yielded age estimates ranging from 3.4 to 3.7 million years ago (Ma). However, biochronological approaches using nonhominin primates suggest an alternative age range between 2 and 2.6 Ma. Based on a new method of hominin biochronology, Thackeray and Dykes have recognized that Sterkfontein Member 4 has a mean age of 2.76 Ma associated with a wide range (circa 2.0-3.5 Ma). In this study, the Sterkfontein skull and skeleton (StW 573), nicknamed "Little Foot" from Member 2 and attributed to A. prometheus, is reassessed. A regression model applied to estimate its age provides a hypothesized date of 3.6 Ma, which compares favorably with the existing cosmogenic dates.

Late-stage evolution of hypogene caves at Tyuya-Muyun (Kyrgyzstan): Quantitative insights from mineral deposits

The Tyuya-Muyun massif in SW Kyrgyzstan hosts a number of caves some of which contain Ra- and U-bearing minerals that were extensively mined in the early 20th century. Previous studies have suggested that the caves of the Tyuya-Muyun have experienced a complex speleogenetic history, including epigene and hypogene processes. Here, we reconstruct the late stages of hypogene processes by studying subaqueous (calcite and barite spars, cave clouds), near-water table (rafts, folia) and vadose (flowstone) mineral deposits in Great Barite and Surprise caves. We determined the chronology (230Th dating), stable isotope composition (δ18O, δ13C and Δ47), and formation temperature (fluid inclusion microthermometry and Δ47) of these minerals and reconstructed the oxygen isotopic composition of the paleo-water (δ18Ow). In contrast to previous hypotheses about cave evolution, we found no evidence of an initial epigenic karst phase. The earliest mineral deposits suggest already hydrothermal conditions, with calcite and barite forming at ∼40–50 °C prior to 600 ka. Cave clouds in Great Barite Cave mark the beginning of the lowering of the groundwater table and also record a decrease in water temperature from 29.7 ± 8.3 °C to 12.7 ± 5.6 °C, as shown by Δ47 thermometry. The latter temperature remained stable, within analytical uncertainties, during the past 600 ka, as indicated by Δ47 results of near-water table and vadose speleothems in Surprise Cave. At the same time, the decrease in δ18Ow suggests a reduced contribution of thermal water and an increased input of colder meteoric water. By around 540–450 ka Surprise Cave emerged from the phreatic zone, as indicated by 230Th ages of the highest folia and flowstone. This lowering of the water table continued until 84 ka and may have been related to the final uplift phase of the Tyuya-Muyun massif and the concomitant incision of the Aravan River forming the Dangi Gorge.

Manifestations of sulfuric acid speleogenesis in the Mulapampa travertine, Central Andes of Peru: evidence from the Gruta con Lago

Sulfuric acid speleogenesis (SAS) is a form of hypogene speleogenesis characterized by the formation of caves in carbonate rocks due to the presence of sulfuric acid. This study focuses on the Gruta con Lago, one of three caves identified in the Mulapampa travertine, located in the central Andes of Peru. These caves are accessed through collapse sinkholes, and much of their morphology results from roof breakdown. The bottom of the studied cave is situated at the current water table. Despite the absence of typical solutional features associated with SAS caves, mineralogical and geochemical evidence of speleogenesis involving H2SO4 has been found in Gruta con Lago. Significant accumulations of gypsum deposits on the cave floor and replacement gypsum crusts on walls – both considered by-products of SAS – are present. Cave gypsum samples exhibit negative sulfur isotopic composition (ranging from -19.4 to -8.2‰) and oxygen (ranging from -9.0 to -1.3‰), which are indicative of sulfide (H2S) oxidation. This article discusses potential scenarios of SAS events in the evolution of hypogene karst in the Mulapampa travertine. It also considers the significance of the proximity of the active volcanoes of the Ampato-Sabancaya Volcanic Complex (ASVC) and seismogenic crustal faults in the formation of a thick travertine cover and the potential for SAS processes.

Taphonomic histories of Quaternary fossil accumulations preserved in Brazilian cave deposits

The taphonomic histories of five cave deposits in Brazil were interpreted, focusing on the accumulation and taphonomic modes. These caves, Complexo Suíço, F3, Toca das Onças, Lapa dos Peixes and Gruna das Três Cobras, show evidence of remains being accumulated through entrapping, sheltering, and water transportation. Cluster Analysis revealed a predominance of irregular breaks and low stages of weathering as the primary taphonomic mode, along with lack of corrosion and abrasion. Factor Analysis also indicated that incrustation played a major role in distinguishing between the deposits. The remains in F3, Toca das Onças, Lapa dos Peixes, and Gruna das Três Cobras caves experienced similar preservation conditions, including fragmentation from reworking, block collapses, exposure to acidified rainwater, incrustation and abrasion from water-borne sediments, and corrosion due to bat guano and acidified water.

Old Fossils, New Information: Insights into Site Formation Processes of Two Pleistocene Cave Sequences in Zambia from Enamel Amino Acid Geochronology

Intra-crystalline protein degradation (IcPD) analysis was undertaken on 80 fossil tooth enamel samples from four taxonomic groups (rhinocerotid, suid, equid, bovid) excavated from two archaeological cave sites in Zambia (Twin Rivers and Mumbwa Caves). Seventy-two (90%) of these fossils showed evidence of closed-system behaviour. The fossils’ relative extent of protein degradation between the sites was consistent with their known ages, with samples from Twin Rivers (Mid-Pleistocene) showing higher levels of degradation than Mumbwa Caves (late Mid-Pleistocene to late Holocene). At Twin Rivers, a potential trend between IcPD and excavation depth was observed, concordant with the working hypothesis of periodic deposition of sediments as slurry flows into a phreatic passage. However, greater depositional and taphonomic complexity was indicated by relatively wide ranges of IcPD values within individual excavation levels. These results are interpreted partly as the consequence of the excavation methods used, alongside reworking within the deposits, which had not previously been recognised. Whilst lack of stratigraphic control limited the investigation of taxonomic effect, one notable difference in the protein breakdown pattern of peptide chain hydrolysis was observed between rhinocerotid in comparison to the other studied taxa. We therefore recommend taxon-specific enamel amino acid geochronologies (AAGs) are developed in future. Whilst lack of comparator datasets meant it was not possible to create a calibrated, enamel AAG for the South-Central African region from these sites, Twin Rivers provides a case study illustrating the complexity of cave formation processes and the importance of direct dating for interpreting archaeological and palaeontological sequences.

Deep desert aquifers as an archive for Mid- to Late Pleistocene hydroclimate: An example from the southeastern Mediterranean

Many efforts have been made to illuminate the nature of past hydroclimates in semi-arid and arid regions, where current and future shifts in water availability have enormous consequences on human subsistence. Deep desert aquifers, where groundwater is stored for prolonged periods, might serve as a direct record of major paleo-recharge events. To date, groundwater-based paleoclimate reconstructions have mainly focused on a relatively narrow timescale (up to ∼40 kyr), limited by the relatively short half-life of the widely used radiocarbon (5.73 kyr). Here we demonstrate the usage of deep regional aquifers in the arid southeastern Mediterranean as a hydroclimate archive for earlier Mid-to-Late Pleistocene epochs. State-of-the-art dating tools, primarily the 81Kr radioisotope (t1/2 = 229 kyr), were combined with other atmosphere-derived tracers to illuminate the impact of four distinguishable wetter episodes over the past 400 kyr, with differences in climatic conditions and paleo-recharge locations. Variations in stable water isotope composition suggest moisture transport from more proximal (Mediterranean) and distal (Atlantic) sources to different parts of the region at distinct times. Large variability in the computed noble gas-based recharge temperature (NGT), ranging ~15–30 °C, cannot be explained by climate variations solely, and points to different recharge pathways, including geothermal heating in the deep unsaturated zone and recharge from high-elevation (colder) regions. The obtained groundwater record complements and enhances the interpretation of other terrestrial archives in the arid region, including a contribution of valuable information regarding the moisture source origin as reflected in the deuterium-excess values, which is unattainable from the common practice analysis of calcitic cave deposits. We conclude that similar applications in other deep (hundred-m-order) regional groundwater systems (e.g., the Sahara desert aquifers) can significantly advance our understanding of long-term (up to 1 Myr) paleo-hydroclimate in arid regions, including places where no terrestrial remnants, such as cave, lake, and spring sediments, are available.

New Quaternary fossils from high elevation cave deposits in Cuba

New Quaternary fossils from high elevation cave deposits in Cuba

Reconstructing Younger Dryas ground temperature and snow thickness from cave deposits

Abstract. The Younger Dryas stadial was characterised by a rapid shift towards cold-climate conditions in the North Atlantic realm during the last deglaciation. While some climate parameters including atmospheric temperature and glacier extent are widely studied, empirical constraints on permafrost temperature and snow thickness are limited. To address this, we present a regional dataset of cryogenic cave carbonates (CCCs) from three caves in Great Britain that formed at temperatures between −2 and 0 °C. Our CCC record indicates that these permafrost temperatures persisted for most of the Younger Dryas. By combining ground temperatures with surface temperatures from high-resolution ground-truthed model simulations, we demonstrate that ground temperatures were approximately 6.6 ± 2.3 °C warmer than the mean annual air temperature. Our results suggest that the observed temperature offset between permafrost and the atmosphere can be explained by an average snow thickness between 0.2 and 0.9 m, which persisted for 233 ± 54 d per year. By identifying modern analogues from climate reanalysis data, we demonstrate that the inferred temperature and snow cover characteristics for the British Isles during the Younger Dryas are best explained by extreme temperature seasonality, comparable to continental parts of today's Arctic Archipelago. Such a climate for the British Isles necessitates a winter sea ice margin at approximately 45° N in the North Atlantic Ocean.

Last interglacial and MIS 9e relative sea-level highstands in the Central Mediterranean: a reappraisal from coastal cave deposits in the Cilento area, Southern Italy

A revaluation of the relative sea-level (RSL) indicators in the Baia di Infreschi (Cilento, Southern Italy) supported by new 30 U/Th dating on speleothems indicates that the upper level of Lithophaga burrows identified by Bini et al. (2020) at ∼9 m a.s.l. and correlated to the Last Interglacial (LIG) highstand should be referred to the highstand of the MIS 9e, whereas the local RSL for the highstand of the LIG is now reassessed at 5.3 ± 0.18 m a.s.l. The upper level of the Lithophaga marker can be followed for ∼12 km along the coast, suggesting a substantial absence of important relative tectonic movements. In the Baia di Infreschi an additional marine indicator, a notch sealed by a flowstone dated ∼110 ka, indicates several phases of RSL stationing below the maximum highstand of the LIG. The presence of flowstones as low as 2 m a.s.l. dated to the MIS 7 shows that the highstand of MIS 7 was probably below the present sea level. All these evidences allow us to reassess the stratigraphy of some archaeological caves in the area, indicating that the sedimentary successions preserved there are older than what was previously believed.

Palaeolithic Cave deposits and Karst evolution in the Venetian Pre-Alps

Palaeolithic Cave deposits and Karst evolution in the Venetian Pre-Alps

The Influences of O2 Availability on the Microbial Activities and Fe Transformations in the Iron Formation Caves of the Southern Espinhaço Range, Brazil

Over 3000 iron formation caves (IFCs) have formed in erosion-resistant Fe(III)-rich rocks throughout Brazil. Microbial Fe(III) reduction occurs in IFCs, where a microbe-rich, Fe(III)-depleted paste (sub muros) is found behind an Fe(III)-(hydr)oxide crust in the ceiling/walls. Microbial Fe(III) reduction in sub muros appears to be responsible for the transformation of Fe(III) to more soluble Fe(II), which is removed, leading to cave formation. This process of biospeleogenesis is likely controlled by O2 availability, which is linked to seasonal changes. Here, we studied the effects of alternating anoxia/oxia on the microbial community and on Fe solubility in banded iron formation (BIF), a rock type consisting of layered Fe(III)-oxide and silicate. Incubations of synthetic pore water, pulverized BIF, and sub muros were prepared and incubated under anoxia, during which BIF-Fe(III) reduction proceeded. During the Fe(III) reduction period, Firmicutes and/or Alphaproteobacteria were enriched, and genes involved in Fe(III) and sulfate reduction were detected in the metagenomes. Fe(II) oxidation genes, which were detected in the fresh sub muros, were not found. Upon the addition of atmospheric O2, Fe(III) reduction was arrested, and incomplete Fe(II) oxidation occurred. Betaproteobacteria, Gammaproteobacteria, and Chloroflexi increased in relative abundance following aeration, and Fe(III) reduction genes were still identified. Our results demonstrate that the sub muros microbial community retains the ability to reduce Fe(III) and drive speleogenesis despite fluctuations in O2 levels.

Sedimentological evolution of the Quibas site: High-resolution glacial/interglacial dynamics in a terrestrial pre-Jaramillo to post-Jaramillo sequence from southern Iberian Peninsula

The sedimentary infill of the Quibas karstic site (Early Pleistocene, southern Spain) represents the only continuous succession with remains of continental vertebrates in Europe from pre-Jaramillo to post-Jaramillo age. The Quibas site, with a significant paleontological record, is dated between 1.1 and 0.9 Ma and offers a unique opportunity to carry out a paleoclimatic reconstruction of the time period immediately after the arrival of the first humans to western Europe. For this reason, defining the dominant sedimentary processes in the different stratigraphic units and the associated paleoenvironment is essential. The Quibas site is made up of two karstic features with two stratigraphic sequences: Quibas-Cueva, containing six lithostratigraphic units, and Quibas-Sima, which contains seven lithostratigraphic units. The detailed description and analyses of the stratigraphic sections have allowed the characterization of various autochthonous and allochthonous facies of cave deposits. Paleoclimatic proxies, inferred from sedimentological analyses, reveal a record of several alternating humid and arid phases resulting from the Early Pleistocene glacial-interglacial cycles, allowing correlation to the marine oxygen isotope record. The lowermost units (pre-Jaramillo) were deposited during a long-lasting interglacial, correlated to MIS 33–31. It was followed by an increase in aridity in the intermediate units of Quibas-Sima and uppermost unit of Quibas-Cueva (Jaramillo), revealing the beginning of a glacial period at the start of the Jaramillo subchron (1 Ma), which can be correlated to MIS 30. The upper Jaramillo and post-Jaramillo units suggest these were deposited in alternating periods of aridity and humid conditions, although less humid than the pre-Jaramillo period, probably representing the MIS 29 interglacial, the MIS 28 glacial and the MIS 27 interglacial.

ORTA TOROS SIRADAĞLARI VE PAZARCIK OVASI SINIRINDA BİR SON AŞAMA NATUFİAN TEKNOKOMPLEKSİ: KAHRAMANMARAŞ'TAKİ YUSUFUN KAYASI MAĞARASI'NIN İLK SONUÇLARI

Yusufun Kayası Cave is located 45 km east of Kahramanmaraş city center. The cave was discovered as part of the “Prehistoric Survey in Kahramanmaraş Province Project” carried out by a team, directed by Cevdet Merih Erek between 2006 and 2012. We suggest that the elements of the lithic material culture from the cave, including lunates, backed bladelets, end scrapers, perforators, sickle elements (on fragments of blade and flakes), denticulated and notched tools, have parallels with those of “Harifian” culture defined from the Negev and Sinai regions. At the same time, there are also traces of technological innovations associated with plant processing and agriculture, including grinding stone and pulverizing tools recovered from the cave deposits. This study aims to describe this new cultural tradition in Anatolia and describes its similarities and differences within the Near Eastern region.

Development characteristic and main controlling factors of the Ordovician karst caves in the Keping area, Tarim Basin

This research endeavors to characterize the primary factors that influence the formation of Ordovician karst caves in the Keping area of China. A 3D digital model of the cave structure and fracture sets was generated using an Unmanned Aerial Vehicle (UAV). The characterization of fracture and cavity development involved the examination of thin sections, fluid inclusion testing, and the analysis of C and O isotopes. Key parameters controlling karst development were identified through the application of multiple linear regressions and statistical analysis. The Ordovician limestone karst cave exhibited four distinct fracture sets. Set 1 consisted of partially filled fractures with a sub-horizontal orientation and a striking direction of SEE, interpreted to have formed during the Middle-Late Caledonian orogeny. Set 2 comprised inclined tensile-shear fractures with a striking direction of NEE, likely formed during the Early Hercynian orogeny. Set 3 included fully filled conjugate shear fractures with variable orientations, which developed during the Indo-Yanshanian orogeny. Set 4 comprised high-angle shear fractures with striking directions of NNE 20–40° and NEE 60–80°, formed during the Himalayan orogeny. Two stages of cave filling deposition were identified. Stage I coincided with the Middle-Late Caledonian Set 1 fractures and can be attributed to the circulation of freshwater fluid. Stage II occurred concurrently with the Early Hercynian Set 2 fractures and can be attributed to deep hydrothermal fluid circulation. The karst caves are interconnected and aligned along a fault zone. The Ordovician limestone possesses high permeability, which facilitates karst development. The lithologies in the Aksu area play a crucial role in cavity formation and dissolution. The development of cavities is influenced by the combined patterns of the fracture system, with larger fault and fracture zones resulting in larger cave sizes. As one moves away from the fault zone, limestone dissolution decreases, resulting in less pronounced karst development.

Climate monitoring in the Caumont cave and quarry system (northern France) reveal near oxygen isotopic equilibrium conditions for carbonate deposition

The study of modern cave deposits forming under near isotopic equilibrium conditions can potentially help disentangle the processes influencing the oxygen isotope system and suitability of stalagmites as archives of past hydrological or thermal changes. We used cave monitoring to evaluate the impact of kinetic isotope fractionation and assess the conditions under which modern cave carbonates form in the Caumont cave and quarry system, located in Normandy, northwest France. Over 20 months, we collected climatological data, dripwater, and modern carbonate samples at 2–4-week intervals at three different stations inside the Caumont cave and quarry system. We find highly stable (10.4 ± 0.3°C – 11.3 ± 0.1°C) temperature in the deeper sections of the Caumont cave and quarry system. The temporal dynamics of δ18Odrip indicates that the drip water composition in Caumont reflects the original (though subdued) signal of precipitation, rather than the impact the seasonal to interannual cave air temperature has on isotopic fractionation. The monitoring reveals that δ13C of modern carbonate is influenced by prior carbonate precipitation that occurs during the summer season when evapotranspiration can minimize effective infiltration. Comparison of δ18O from dripwater and modern calcite, precipitated on glass plates and collected every two to four weeks, reveals that modern calcite forms near oxygen isotope equilibrium. A Hendy test on modern carbonate deposited on a stalagmite-shaped glass flask over 20 months confirms this finding because neither does δ13C increase with distance from the apex, nor are δ13C and δ18O positively correlated. We conclude that the δ13C signal in speleothems reflect summer (and longer-term) prior carbonate precipitation in response to effective infiltration dynamics, and that the δ18O signal likely reflects annual to multi-annual changes in the composition of precipitation above the cave.