The unequivocal global warming of the climate system and the clear influence of human activities underscore the urgency of addressing the current challenge of Earth's warming. Not only many ecosystems but the whole Earth System is being affected, and in some cases, knowledge about the impact of climate change remains limited. A good example of this are the cave pearls, which are highly interesting due to their particular geochemical fingerprint and also from the perspective of natural heritage.

The mountain regions of the Catalan Pyrenees are experiencing more pronounced temperature increases than the rest of the territory, which intensifies the impacts of climate change in this area. Regarding precipitation, and as is the case throughout the rest of Catalonia, all projections seem to indicate a significant reduction in the annual number of days with light precipitation (20 fewer days) and an increase in the maximum duration of dry spells (20 more days). In this context, one might wonder how this 'new hydroclimatic variability' is altering the environmental conditions of karst cavities. Frequent observations by speleologists reveal a widespread trend toward drier conditions inside caves. More intense droughts could lead to a reduction in the water level of the gours where the pearls grow, a reduction that could significantly hinder their growth.

Cave pearls, technically known as pisolites or oolites depending on their size, represent a type of speleothem growth that is much less known than stalagmites and stalactites. They form rare, difficult-to-find deposits that are still poorly studied and are located on the floors of certain underground cavities. Unlike other stone formations, they are not attached to the rock due to the vibration of the water in the basin where they are found, a vibration caused by the dripping that sustains it. These are complex processes, highly sensitive to environmental variations. As such, they present a potential vulnerability, yet still unknown, to situations arising from the current climate emergency, drought, and human access. The scientific understanding of this heritage (particularly as a record of climate change) and its dissemination must contribute to preserving them from the current irreversible damage and mass spoliation.

This study aims to carry out a geochemical and mineralogical characterization of cave pearls from 15 cavities located within the Orígens Geopark, in the Catalan Pyrennes (NE Spain). The cavities are made of different lithologies (limestones, conglomerates, and sandstones) and include various geomorphological units. The methodology incorporates elemental and mineralogical analyses at both macro and micro scales using XRF, SEM-EDS, XRD, and Raman Spectroscopy, alongside crystallography, X-ray tomography, and advanced 3D imaging techniques. Innovative approaches to imaging and microanalysis will also be utilized.

Our data and analysis show the high richness and geochemical variability of cave pearls in the Orígens Geopark, with high potential to extract useful information about the impact of climate change on karstic systems.

How to cite: Cisneros, M., Ibáñez-Insa, J., Roqué, J., Jiménez, A., Álvarez, S., Auroux, L., and Giralt, S.: Cavern pearls of the Lluis Auroux's Collection: geochemical and mineralogical characterization on caves from the Geoparc Orígens (Catalan Pyrenees), EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7077, https://doi.org/10.5194/egusphere-egu25-7077, 2025.

Cave carbonates offer insights into past environmental and climate change. A unique type of these deposits, cryogenic cave carbonates (CCCs), form by a mechanism known as cryogenic crystallization. CCCs may form through: (1) rapid freezing of thin water films on ice surfaces, creating small crystals (typically, <1 mm), and (2) slow freezing of water in pools, creating larger crystals (up to several cm in size). These two types of CCC show distinct stable isotope compositions. From a paleoclimatological point of view, CCCs of the second type are an indicator of past permafrost conditions¹. However, the details of their formation are still not fully understood, as no actively forming CCCs of this type have been observed in nature.

To study how the freezing proceeds and how it influences the geochemical signature and morphology of the cryogenic crystallization products, we employed several methods for forming cryogenic carbonates under controlled conditions in the laboratory. (1) Cryogenic carbonates were produced via bottom-up solution freezing, by lowering a plastic bottle filled with a Ca-bicarbonate solution into a -15 °C medium. The freezing times for the bottom and top layers varied between three and ten hours. (2) Cryogenic carbonates were also precipitated from a saturated Ca-bicarbonate solution via slow (several days) and uniform freezing at -2 °C in a freezer. To control the direction of freezing and enhance the top-down freezing process, the flask containing the bicarbonate solution was placed in an insulated box. After the experiments, the first- and last-formed carbonates were separated by sampling of the formed ice. Marked differences in the crystal size and the oxygen and carbon isotope compositions of the first- and last-formed carbonates were observed. The δ¹³C and δ¹⁸O values of synthetic cryogenic carbonates align with the field of the fast-forming natural CCCs. However, when compared with parent solutions, they are closer to the values of the field of CCCs² forming in freezing pools. The results highlight the importance of knowing the C isotopic composition of the solution’s dissolved inorganic carbon in isotope-based classification of CCCs, and are relevant for understanding the environment in which CCCs form.

We acknowledge the financial support of the NKFIH ANN141894 grant.

References:

¹ Žák, K., Onac, B.P., Kadebskaya, O., Filippi, M., Dublyansky, Y., Luetscher, M. (2018): Cryogenic mineral formation in caves, in: Perşoiu, A., Lauritzen, S.-E. (Eds.), Ice Caves, 123-162, Elsevier, Amsterdam.

² Spötl, C., Koltai G. & Dublyansky Y. (2023) Mode of formation of cryogenic cave carbonates: Experimental evidence from an Alpine ice cave. Chemical Geology, 638, 121712. DOI: 10.1016/j.chemgeo.2023.121712.

How to cite: Németh, P., Demény, A., Lázár, A., Koltai, G., Dublyansky, Y., and Spötl, C.: Cryogenic carbonate synthesis by controlled solution freezing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18074, https://doi.org/10.5194/egusphere-egu25-18074, 2025.

Speleothem fluid inclusion isotope analysis provides the oxygen and hydrogen isotope compositions of the parent water from which the carbonate was precipitated. In contrast to the carbonate isotopes, it is not affected by kinetic isotope effects or cave air temperature. However, in-cave evaporation has been identified as a potential control on drip water isotopes if drip rates are slow and or relative humidity in the cave is low.

Rainfall isotope compositions generally plot close to the global meteoric water line (GMWL) in a plot of d²Hversus d¹⁸O that can be described by the following regression equation: d²H = 8*d¹⁸O + 10. A lower deuterium excess (d-excess) value indicates post-condensation evaporation, and different fractions of evaporation typically result in so-called evaporation lines with shallower slopes. Recently it was shown that in-crusher evaporation results in water loss during analysis, which may significantly affect the speleothem fluid inclusion isotope composition. For fluid inclusion isotope compositions that have low d-excess values, it is thus key to find out where evaporation took place.

In this study, we examine the effect of analytical evaporation by quantifying the water loss during analysis. We target two layers with different calcite fabrics from a flowstone of Touhami Cave (GTOF2), Morocco, as well as a speleothem from Scladina Cave, Belgium. The Moroccan fluid inclusion isotope data agree well with the drip water isotope composition from a cave nearby. The white opaque layer from GTOF2 has high water contents of 3.4 µl/g, whereas the second transparent layer has only 0.12 µl/g. The speleothem from Scladina Cave yielded 2.0 µl/g. We observed that all replicates lose water up to 39% by evaporation, but only the Scladina speleothem shows a clear relationship between fractional water loss and d-excess. The replicates of the low water content layer in GTOF2 plot on an evaporation line, but the slope is steeper compared to the evaporation line from the Scladina speleothem. We suggest that the Touhami Cave flowstone may have been affected by in-cave evaporation.

How to cite: Wassenburg, J. A., Vonhof, H. B., Basu, S., Cleary, D. M., Yang, Y. S., Oh, Y., Cheng, H., and Spoetl, C.: Quantifying evaporation during fluid inclusion isotope analysis in speleothem samples, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14953, https://doi.org/10.5194/egusphere-egu25-14953, 2025.

The application of organic carbon-based proxies, particularly biomarkers, to speleothem archives has greatly increased due to methodological and analytical advances. These reconstructions rely on the critical assumption that the analyzed proxy shares the same age as the surrounding archive matrix, as direct measurement of the biomarker age remains challenging due to very low concentrations.

We have developed a dataset of globally distributed bulk organic carbon radiocarbon ages from speleothems. Comparison with coupled carbonate radiocarbon ages, and where applicable, U-Th ages, shows that the speleothem organic carbon fraction is predominantly older than the depositional age (by 600 - 15,000 years). This discrepancy seems largely unaffected by climate conditions and ecosystem type, suggesting that aging of organic matter through storage and reworking is a widely occurring feature of karst systems.

Radiocarbon measurements of drip water organic carbon in a temperate karst system in Switzerland confirm that dissolved organic carbon ages in the karst system (and is not, for example, related to processes during incorporation into the speleothem carbonate matrix), with a strong influence of hydrology. Fluorescence and high resolution mass spectrometry allow us to investigate the processing and transformation of organic matter in the subsurface.

Our results remain so far constrained to the bulk organic carbon phase, and therefore we can only infer on how different biomarkers are affected by pre-aging in the karst system. Nevertheless, we highlight the complexity of carbon transport and transformation in the karst subsurface, underscoring the need for careful screening of samples and biomarkers used for paleoenvironmental reconstructions from speleothem organic matter.

How to cite: Lechleitner, F., Sarah, R., Xue, G., Huber, T., Luetscher, M., Guidobaldi, G., Haghipour, N., Endres, L., Stoll, H., Chiaia-Hernández, A. C., and Cirelli, S.: Radiocarbon evidence for aged speleothem organic matter: what does this mean for the interpretation of speleothem biomarker records?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15460, https://doi.org/10.5194/egusphere-egu25-15460, 2025.

Speleothems, renowned for their potential as continuous paleoenvironmental archives spanning thousands of years, are particularly valuable due to reliable age determination via the 230Th/U230Th/U-method. The closed-system nature of cave environments and the chemical stability of speleothems allow for the preservation and analysis of organic substances alongside traditional proxies such as stable isotopes and trace elements. Among organic compounds, sterols emerge as promising biomarkers owing to their chemical stability in oxygen-limited environments, and distinct origins from plants, animals, and microbial processes.

Cholesterol and sitosterol, representing sterols derived from animals and plants, respectively, are precursors to stanols, which are microbially reduced sterols, often traceable to faecal inputs. Notably, coprostanol serves as a key marker for human activity due to its predominance in human faeces. Despite the widespread application of sterol-based biomarkers in soil and sediment studies, their use in speleothem research remains nascent, largely due to the challenges posed by the complex mineral matrix and low concentrations of organic analytes.

To overcome these obstacles, a method combining stir bar sorptive extraction (SBSE) with a polydimethylsiloxane (PDMS) phase was developed, following acid dissolution of speleothem samples. Subsequent analysis was performed using high-performance liquid chromatography coupled with atmospheric pressure chemical ionization high-resolution orbitrap mass spectrometry (HPLC-APCI-HRMS), which provides exceptional resolution and sensitivity. This novel methodology not only enhances the extraction and analysis of sterols from speleothems but also establishes a pathway for expanding their use in paleoenvironmental and anthropogenic reconstructions.

How to cite: Schäfer, J. and Hoffmann, T.: Sterol Biomarkers for Paleoenvironmental and Anthropogenic Tracing in Speleothems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18153, https://doi.org/10.5194/egusphere-egu25-18153, 2025.

The research investigated cave deposits and stalagmites in two caves within the karst area of the Madingou region, Republic of the Congo, with a focus on biocorrosion features and guano deposits prevalent in these sites. A systematic inventory of biocorrosion features in the studied caves was complemented by geochemical analyses of sediments and corroded speleothems, providing valuable insights into the underlying processes. To monitor environmental conditions, a seasonally based approach was employed, involving temperature recording, punctual CO₂ measurements, and in-situ parameter monitoring during each sampling period. These efforts contribute to a detailed understanding of speleogenesis processes, particularly the influence of bat guano-induced corrosion.

Field studies revealed remarkable observations of cave morphology, highlighting intriguing biocorrosion features such as cupolas, guano-holes in the ground, and bell holes in the roof. These features closely resemble similar formations documented in other regions, including France and Slovakia. The observed elements have sparked reflections on their significance in the late morphological evolution of caves. Understanding the role of bat guano in shapingmorphology could shed light on the broader processes influencing cave evolution in various contexts.

Two samples were collected from the dark-colored superficial sediments, along with two core samples from monitored stalagmites and one sample from a corroded speleothem, all from two bordering caves in the Madingou region. These samples underwent elementary chemical analysis, revealing that the sediments contained 11% CaO and 24% P₂O₅, while the corroded speleothem exhibited 55% CaO and 47% P₂O₅. The high phosphate (P₂O₅) and calcium oxide (CaO) concentrations, confirm the direct impact of biocorrosion driven by bat guano on the evolution of cave features.

The process of biocorrosion is further supported by environmental parameters, including an elevated CO₂ concentration that vary between 480 and 500 ppm, higher than the atmospheric average (~400 ppm), and cave temperatures ranging between 19°C and 25°C. These conditions, which are ideal for microbial activity, accelerate the decomposition of bat guano and promote the formation of phosphoric acid and carbonic acid. These acids enhance carbonate dissolution and the precipitation of phosphate minerals, leading to significant chemical and structural alterations in the cave system over time. The impact of bat guano on cave evolution is also temporally contextualized by C-14 dating, which places the deposition of the superficial sediment layer at 1956 ± 28 BP. This dating aligns with a period of guano accumulation and biocorrosion activity, highlighting the longstanding influence of bat colonies on the cave's geochemical environment.

In summary, the high phosphate content within sediment and speleothems, carbonate corrosion, coupled with the radiocarbon-dated guano deposits, suggest that biocorrosion induced by bat guano decomposition has been a primary driver of recent cave morphology evolution in the Madingou region for at least two millennia. This biogeochemical activity reflects a dynamic interplay of biological and chemical processes under specific environmental conditions, resulting in both chemical modification and structural caves features reshaping.

How to cite: Lahogue, P., Bazebizonza, N., Verheyden, S., Boudin, M., Boudzoumou, F., and Arfaoui, I.: Unveiling the biogeochemical role of bat guano in shaping cave morphology in the Madingou region, Republic of the Congo, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16788, https://doi.org/10.5194/egusphere-egu25-16788, 2025.

Our work on a speleothem in the Hotton cave reveals a 5000-year record of past floods in the Hotton cave through deposition of detrital layers in a flowstone covered by mud during the exceptional 2021 flood. The palaeorecord reveals other such exceptional floods around 1550 CE (Common Era), 30 CE and 350 BCE (Before Common Era). Further down, a period between 3.3 BCE and 2.6 BCE shows ‘dirty calcite’ with several smaller detrital layers indicating a period with much more regular floods. In the frame of the Leap Project (learning from the past - The impact of abrupt climate changes on society and environment in Belgium - www.leap-belgium.be), we investigate possible relations between the environmental  changes and past human activities. In order to construct high resolution trace element curves as a proxy for past water availability, a procedure for LIBS analysis of speleothems is set up at the Institute of Natural Sciences in Brussels, Belgium. A 2D spectral image of a few millimeters broad is taken along the growth axis of the speleothem. A curve is constructed by averaging the data along horizontal lines of the 2D analysis. It is a rapid and minimal destructive method to obtain trace elemental curves of Mg, Sr, Ba, and other elements such as Pb, Cu, Zn,.. Up to now the method is rather qualitative, but a semi-quantitative analysis is in progress.

The interest of these climate and environmental related data, is that they are very visual, concrete traces of past climate changes. Speleothems and their records of floods are a strong educational tool for citizens that feel not concerned about climate change. The dissemination of our results through events organized by the UNESCO Global Geopark Famenne-Ardenne aims at engaging inhabitants with climate science and awareness.

How to cite: Verheyden, S., Burlet, C., Delaby, S., Cheng, H., Jia, X., Pincé, P., Deforce, K., Snoeck, C., Crombé, P., Vandendriessche, H., Leonard, H., Capuzzo, G., Boudin, M., and Wojcieszak, M.: Floods and water availability reconstructions from speleothems through Laser-induced break down spectrometry (LIBS) with implications for archaeological work and citizen engagement in the UNESCO global geopark Famenne-Ardenne. , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17668, https://doi.org/10.5194/egusphere-egu25-17668, 2025.

Comparing long-term climate variability with documentary data for the last millennium is challenging in regions where well-resolved natural records are lacking. In Cyprus, historical data of famine outbreaks, plagues and locust waves were retrieved from a variety of historical documents. These events are considered as societal indicators as they reflect the vulnerability of the Cypriot society towards environmental and climatic change from the late Lusignan’s to the Early British colonial period. The aim of this study within the HIGH-PASM project is to explore the relationship between local climate variability and locust waves, plagues and famine outbreaks.

An 8 cm-high actively growing stalagmite was collected from Hot cave in the Kyrenia range (Cyprus). U-Th dating and lamina counting were combined to produce an age model of the last ~700 years. We applied high-resolution stable isotopic (ẟ¹⁸O, ẟ¹³C) and trace element (Mg, Sr) analyses to establish climate proxy records and compare them to historical records and observational data. First, statistical analyses (normalization, volatility) were conducted on the isotope time-series to evaluate the intensity of humid/dry peaks and to identify periods with strong/weak fluctuations. Second, 875 recorded events were compiled from various historical sources (primary, secondary, compilations) and homogenized. Third, both natural (continuous) time-series and historical (discrete) data were compared using several statistical methods. 

The comparison between the occurrence of these three types of historical events shows that 36% of locust waves and famines occurred within the same year and a similar synchronicity was found between famines and plague outbreaks. Plagues and locust waves, however, did not occur significantly synchronously. Statistical analyses between the ẟ¹³C volatility index and the number of locust waves, plagues, and famines show whether certain combinations of dry/wet and volatile/non-volatile conditions promote any of the three different disasters. Early results show that all three types of events occurred during wet and non-volatile (low signal oscillation) periods. This is consistent with the ecological niches of Dociostaurus maroccanus (locust specie) and Yersinina pestis (zoonotic bacterium that causes plague) which require a slightly wet climate to proliferate. However, this applies less to famines, as many famines also occurred during dry periods (e.g., in the 19^th century).

How to cite: Nehme, C. and the ANR HIGH-PASM project: Comparing climate variability with historical datasets from Cyprus: significance, strengths and limitations , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17008, https://doi.org/10.5194/egusphere-egu25-17008, 2025.

Using 15 ²³⁰Th dating of a stalagmite (SN33) from Shennong Cave, Jiangxi Province, southeastern China, along with 140 δ¹⁸O results, we reconstructed the evolution of the East Asian Summer Monsoon (EASM) during the Late Holocene between 3.2 and 2.5 ka B.P., with an average resolution of 4 yrs. During this interval, a pronounced positive δ¹⁸O excursion was observed between 2.97 and 2.68 ka B.P., marking the occurrence of the 2.8 ka weak monsoon event in southeastern China. This event began at 2965 ± 13 a B.P. and ended at 2677 ± 47 a B.P., characterized by an asymmetric "double-plunging" structure. Through centennial-scale variations in δ¹³C, trace elements, δ²³⁴U, and growth rate of stalagmite SN33, we infer that southeastern China was in a wetter state during 2.8 ka event. Comparison with other geological records further supports that, while southeastern China indeed experienced humid conditions during this period, other regions were in a state of drought. The 2.8 ka B.P. climatic anomaly had profound impacts on agriculture, population migration, and cultural transitions in the East Asian monsoon region. In China, populations migrated to the warmer and more humid region in southeastern of lower reaches of the Yangtze River Valley (YRV), facilitating the development of agriculture and culture in this region. Meanwhile, the collapse of the Zhou Dynasty in China and the decline of the Songguk-ri culture in Korea were also responses to the cooler and drier climate conditions during the 2.8 ka event.This precipitation pattern may have been influenced by a strengthened westerly jet stream and the Western Pacific Subtropical High (WPSH) during 2.8 ka B.P..  The internal dynamics and transitional characteristics between the 2.8 ka and 8.2 ka events suggest that both weak monsoon events in the Holocene may have been driven by a common mechanism, likely associated with a weakening of the Atlantic Meridional Overturning Circulation (AMOC). Additionally, the significant decline in solar activity during the latter phase of the 2.8 ka event indicates that centennial-scale variations in East Asian monsoon circulation were likely co-driven by solar activity and high-latitude climatic changes in the Northern Hemisphere.

How to cite: Zhang, X., Zhang, H., Wang, M., and Cheng, H.: The 2.8 ka abrupt climate event in East Asian Monsoon region: High-resolution stalagmite records from southern China, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8706, https://doi.org/10.5194/egusphere-egu25-8706, 2025.

Late Pleistocene climate of the European Alps was characterized by orbitally forced, high-magnitude oscillations in temperature and glacial ice extent. Beyond the Last Glacial Maximum, however, the geographic extent of continental glaciation is notably difficult to constrain, due to the erosion and reworking of associated surficial deposits. Subglacial speleothem growth occurs when warm-based ice sheets cover karst terrain, providing a thermal buffer to ground temperature and a source of liquid water infiltration. In place of carbonic-acid dissolution from the soil zone, the oxidation of sulfide minerals provides a source of acidity to facilitate carbonate dissolution and vadose-zone precipitation. The proxy identification of subglacial processes can therefore serve to constrain ice-sheet evolution from absolutely dated speleothems, but these techniques have yet to be systematically developed. Herein we present a novel composite record of climatic change across MIS-12, -11, and -10 from three stalagmites in Klaus Cramer Cave, a high-elevation site located in the northern Alps of western Austria. Stable-isotope values of oxygen (carbon) are low (high) during glacial episodes that bound the MIS-11 interglacial. When warm-based ice is likely to be present above the cave, δ¹³C exceeds +4‰, signaling that sulfuric-acid dissolution became dominant in the epikarst. To investigate this process further, we measured δ³⁴S and δ¹⁸O in speleothem sulfate, which confirm that pyrite was the primary sulfur source and elucidate redox conditions in both subglacial and soil-dominated systems. Glacial periods also exhibit abrupt and dramatic contrasts to MIS-11 with regard to major- and trace-element concentrations, including a ~20-fold increase in sulfur concomitant with elevated Mg and Sr. This pattern is consistent with a marked increase in prior calcite precipitation associated with sulfuric-acid dissolution that would have elevated initial Ca²⁺ in the system. Finally, we assess trace elements in the context of provenance analysis as a potential indicator of enhanced glacial weathering at the ice-rock interface. Collectively, this suite of geochemical proxies can identify precisely when warm-based ice advanced or retreated across the specific location and elevation of Klaus Cramer Cave in the total absence of evidence from conventional glacial geomorphology.

How to cite: Baker, J., Moseley, G., Honiat, A., Wynn, P., Edwards, R. L., and Spötl, C.: Novel proxy constraints on subglacial speleothem growth in the Northern Alps bounding the MIS-11 Interglacial, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20167, https://doi.org/10.5194/egusphere-egu25-20167, 2025.

Speleothems are invaluable archives of past climate variability and offer important insights into monsoon dynamics across Southeast Asia. Different isotope systems have been employed to characterise autumn monsoon in this region, but multiple influencing factors render the interpretation of isotope proxy records ambiguous. To gain novel insights into regional vegetation and temperature changes, novel proxies are required. Here, we combine traditional speleothem stable isotopes (δ¹⁸O and δ¹³C) with speleothem thermometry (TEX₈₆) and lignin oxidation products (LOP) analyses, to provide a more comprehensive understanding of past environmental changes in Central Vietnam. Specifically, we aim to:

1. Reconstruct cave air temperature variations using TEX₈₆.

2. Assess vegetation and environmental changes through LOP analysis.

3. Evaluate the response of these proxies to known climate forcing mechanisms, including Northern Hemisphere summer insolation, sea surface temperature anomalies, and shifts in the Intertropical Convergence Zone.

A stalagmite record from Central Vietnam, spanning the last glacial and onset of the Holocene (35 – 10 ka BP), provides a unique opportunity to reconstruct glacial to Holocene temperature changes and the response of regional hydroclimate and vegetation. Preliminary TEX₈₆ results suggest a temperature shift of at least 2°C from fully glacial to Holocene conditions. LOP results suggest that the vegetation in Central Vietnam changed from hardwood deciduous vegetation types (0.37 S/V, 0.33 C/V) to an increase in softwood vegetation types (0.1 S/V, 0.11 C/V), respectively.  Our findings have implications beyond Southeast Asia's paleoclimate. Validating these novel biomarker systems (TEX₈₆ and LOP) against more traditional stable isotope ratios (δ¹⁸O and δ¹³C), we aim to elucidate changes in moisture budget and sources, and seasonality.

How to cite: Snowling, C., Wolf, A., Breitenbach, S. F. M., Bendle, J., Martínez-García, A., Schäfer, J., McGee, D., Jost, A. B., Limbert, D., and Ersek, V.: A Multiproxy Approach to study Vegetation and Temperature Changes since the Last Glacial in Central Vietnam., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-896, https://doi.org/10.5194/egusphere-egu25-896, 2025.

Global climate evolution since the Last Glacial Maximum is well understood but large areas of continental Eurasia are still underrepresented, masking regional disparities. While some regions have high-resolution paleoclimate records, there are significant spatial and seasonal differences in reconstructed trends, particularly with regard to Early Holocene temperature. The Western Caucasus region of the Eastern Black Sea margin, comprising modern Russia and Georgia, is of high historical and archeological significance with abundant Paleolithic sites. It served as a corridor for migration and settlement of early modern humans and Neanderthal alike, influencing the development of agriculture and major cultural achievements. Although the abundance of limestone caves within the rich karst terrain provides ample opportunity for paleoclimatic reconstruction from speleothem analysis, this approach has scarcely been utilized. Here we present novel speleothem records from three caves—Vorontsovskaya, Novoafonskaya, and Abrskil—that collectively span the last 34,000 years with minor hiatuses.

By analyzing high-resolution stable isotope data (δ¹⁸O, δ¹³C) from speleothems in these caves, we aim to evaluate the regional response to major climate events from the Late Pleistocene to the Holocene. Our approach involves high-precision Uranium-Thorium dating and micromilling for isotopic analysis corresponding to multidecadal resolution. Preliminary results indicate semi-continuous data, which will allow us to identify key perturbations and trends, such as the Younger Dryas, Heinrich, and Dansgaard-Oeschger events. These will be correlated with other regional and global data sources to provide a clearer picture of past regional climate dynamics and their connection to global climate trends. Understanding the climatic conditions and moisture sources—such as influences from the Black Sea via westerly wind systems, Mediterranean, and continental sources—may help clarify the susceptibility of regional agriculture to drought while contributing to a better understanding of global climate evolution. Additionally, identifying the link between regional climate processes and larger-scale climatic shifts can provide valuable insights for predicting future climate scenarios in the region.

How to cite: Rührer, M., Schneck, T., Chervyatsova, O., Dbar, R., Zakharov, E., Dublyansky, Y., Spötl, C., and Baker, J.: Constraining the climate of the Western Caucasus from the Late Pleistocene to Holocene through isotopic analysis of speleothems, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17146, https://doi.org/10.5194/egusphere-egu25-17146, 2025.

During the Last Glacial Period, millennial-scale abrupt climate events were closely linked to the weakening of the Atlantic Meridional Overturning Circulation (AMOC). This weakening is also significantly associated with the increasing frequency of modern extreme climate events in the context of global warming. However, geological records detailing regional climate responses in southeastern China during these events, particularly the Heinrich cold events, remain limited. In this study, we analyze climate characteristics during the Heinrich Stadials (HS1-HS4) using multiple proxies from the stalagmite YXG01, which was collected from Yindi Cave in Huangshi City, Hubei Province (located in the lower reaches of the Yangtze River). The proxies include δ¹³C, δ¹⁸O, Mg/Ca, Sr/Ca, and Ba/Ca, and the dating spans from 47.47 to 11.92 ka BP. Our results show that during HS1-HS4, δ¹⁸O values in the stalagmite exhibit significant positive excursions, indicating a weakening of the East Asian summer monsoon (EASM). In contrast, δ¹³C, Mg/Ca, Sr/Ca, and Ba/Ca ratios show negative excursions. Furthermore, stalagmite growth rates significantly increased during these stadials, reflecting more favorable hydroclimatic conditions. On the orbital timescale, our δ¹⁸O variations also show inverse relationships with δ¹³C, Mg/Ca, Sr/Ca, and Ba/Ca ratios, suggesting that the stalagmite δ¹⁸O variations are anticorrelated with changes in rainfall in southeastern China. These findings support the hypothesis of a "tripole precipitation pattern" in monsoonal China, where stronger EASM periods correspond to more precipitation in North and South China and less in Central-East China, while weaker EASM periods show the opposite pattern. Nevertheless, during the Last Glacial Period, both on the orbital timescale and during Heinrich Stadials (HSs), the robustness of the tripole precipitation pattern in monsoonal China still needs to be further validated through the use of well-dated and reliable precipitation proxies.

How to cite: Wang, M., Zhang, H., Zhang, X., and Cheng, H.: Hydroclimate Variations in Southeastern China During the Last Glacial Period: Insights from Multi-Proxy Stalagmite Records, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-8705, https://doi.org/10.5194/egusphere-egu25-8705, 2025.

Understanding how climate change manifests across the Mediterranean basin is critical for predicting the impacts of future climate change. The Black Sea region (BSR) is one of the most vulnerable areas of the Mediterranean climate change hotspot, owing to its high sensitivity to both local and global-scale climate feedbacks¹. However, few paleoclimate records exist with sufficient resolution, and length, to fully assess significance of these feedbacks on timescales exceeding the window of instrumental observation². Here, we present a ~230-year-long, seasonally-resolved stable isotope record record of effective moisture and temperature variability from stalagmite So-11, which grew in Sofular Cave (Northern Türkiye) between 1779 and 2008 CE. The sample contains 229 continuous, well-developed laminae couplets with a mean wavelength of ~0.95 mm a^-1, suggesting that each dark-to-light couplet corresponds to one calendar year. This assumption is supported by two U-Th ages, which show good agreement with the layer-counted chronology generated using the date of collection (2008 CE) as an upper anchor point. Minima in δ¹³C closely track the dense, dark, compact calcite layers, and are typically followed by a distinct δ¹³C peak in conjunction with formation of white, porous calcite layers. We interpret these oscillations as seasonal changes in effective moisture, with the lowest δ¹³C values corresponding to high drip rates, lower CO₂ degassing, and weaker fractionation during winter months – reflecting the high responsivity of the Sofular Cave system to transient changes in local precipitation^3,4. Marked changes in the geochemistry of So-11 also coincide with the Little Ice Age (1850 to 1870 CE), and the progressive increase in global atmospheric CO₂ in response to increased fossil fuel combustion during the 20th and 21st centuries⁵. Our results underscore how high-resolution, speleothem-based paleoclimate reconstructions can provide important context not only for constraint of global circulation model (GCM) simulations, but also closer examination of human-climate-environment interactions during the Late Holocene. 

~~

¹Giorgi, F. (2006) Geophysical Research Letters 33(8):  L08707
²Burstyn, Y. et al. (2019) Quaternary 2:16
³Göktürk et al. (2011) Quaternary Science Reviews 30: 2433-2445
⁴Rudzka, D. et al. (2011) Geochimica et. Cosmochimica Acta 75 : 4321–4339
⁵Bauska, T. K. et al. (2015) Nature Geoscience 8: 383–387

How to cite: Paine, A., Held, F., Cheng, H., and Fleitmann, D.: A seasonally resolved late Holocene paleoclimate record from Sofular Cave, Northern Türkiye., EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11210, https://doi.org/10.5194/egusphere-egu25-11210, 2025.