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We present a 500‐year precipitation‐sensitive record based on co‐varying speleothem δ18O values and Mg/Ca ratios from Larga cave in Puerto Rico. This multi‐proxy record shows that the evolution of rainfall in the northeastern Caribbean was characterized by alternating centennial dry and wet phases corresponding to reduced versus enhanced convective activity. These phases occurred synchronous with relatively cool and warm tropical Atlantic sea‐surface temperatures (SSTs), respectively. While the observed pattern suggests a close link of northeastern Caribbean rainfall to the Atlantic Multidecadal Variability, a regional comparison reveals intermittent regional heterogeneity especially on decadal timescales, which may be related to a superimposing influence of the Pacific and Atlantic basins. Furthermore, the speleothem‐based hydroclimate reconstruction indicates a significant volcanic impact during the past two centuries, and further reveals a potential solar signal in the preceding three centuries. We posit that the forcing likely shifted from solar to volcanic during the eighteenth century in being an important source of multidecadal to centennial Caribbean rainfall variability. The link between convective rainfall and natural forcing may be explained through a modulation of SST variations in the tropical Atlantic and Pacific oceans. Plain Language Summary: Climate change is expected to affect rainfall throughout the Caribbean and Central America, where over 200 million people are heavily dependent upon rain as their main source of freshwater. We have looked at how the amount of rainfall in the Caribbean has changed through time, and possible reasons for these changes, to inform predictions of future rainfall patterns for the region. Cave mineral deposits, also known as speleothems, can be used to assess the amount of regional rainfall in the past by looking at their slight changes over time in the mineral's chemical composition. We created a record of Caribbean rainfall spanning the last five centuries using a speleothem from Puerto Rico. Our results indicate that rainfall changes since the sixteenth century were strongly influenced by changes in temperatures of the surface waters of the Atlantic Ocean. We further found that changes in the sun's brightness and volcanic eruptions may alter Atlantic Ocean sea‐surface temperature, which in turn affect the overall changes in Caribbean rainfall patterns. Key Points: Speleothem‐based Puerto Rican rainfall reconstruction shows prominent multidecadal‐to‐centennial variability during the past five centuriesPuerto Rican rainfall fluctuations are linked to solar variations before the eighteenth century and volcanic forcing thereafterCaribbean Sea‐surface temperature anomalies as part of the Atlantic Multidecadal Variability emerge as robust precursor of rainfall amounts [ABSTRACT FROM AUTHOR]

A speleothem collected from Palco Cave (Puerto Rico) spans the 8.2 ka event, a time interval associated with fluctuations of Atlantic Ocean circulation and possible drying in the Caribbean region. While stalagmite δ18O, δ13C, and Mg/Ca data do not show a sustained change in mean state over the 8.2 ka event, the proxies provide robust evidence for three abrupt fluctuations toward drier conditions in rapid succession, each lasting less than two decades, occurring at 8.20, 8.14, and 8.02 ka BP. A cave monitoring program at Palco Cave supports the interpretation of the speleothem proxy records. Because changes in the position of the Intertropical Convergence Zone (ITCZ) are directly coupled to sea-surface temperature variations in the North Atlantic, we hypothesize that cold events in the North Atlantic temporarily limited the northward migration of the ITCZ and tropical rain belt in boreal summer during these abrupt drying periods. The speleothem record suggests that the 8.2 ka event was associated with rapid rainfall fluctuations in the northern Caribbean followed by a comparably warm and wet phase after the 8.2 ka event. This enhanced variability during the transitional period of the deglaciation appears to be linked to a fast coupling between interacting oceanic and atmospheric processes. This involves, in particular, the Atlantic Meridional Overturning Circulation in modulating interhemispheric heat transport. [ABSTRACT FROM AUTHOR]

Here we present an electrochemical method for the anodic oxidation and subsequent degradation of lignin in speleothems to utilize the resulting lignin oxidation products (LOPs) as paleo‐vegetation markers. LOPs were analyzed using an ultra‐high performance liquid chromatography (UHPLC) system coupled to a high‐resolution mass spectrometer (HRMS). The method presented here achieved comparable or even higher LOP concentrations than established CuO and CuSO4 oxidation methods. The method represents a new tool for the analysis and reconstruction of paleo‐vegetation and has the potential to be applied to other climate archives. [ABSTRACT FROM AUTHOR]

We present a new speleothem trace element and stable isotope record, which extends previous paleoclimate evidence from Cuban speleothems to the last 96 ka. Multiple proxies were used to reconstruct Caribbean hydroclimate and vegetation variability on orbital to millennial timescales. In particular, our proxies indicate a shift to more abundant C4 (compared to C3) vegetation and/or reduced soil activity during the Last Glacial Maximum. Our results confirm the close link of Caribbean precipitation to North Atlantic climate variability, insolation and the strength of the AMOC. The associated variations in Caribbean SSTs and the shift of the ITCZ led to substantial changes of the hydrological cycle. During Heinrich stadials and the Younger Dryas, climatic conditions in Cuba were comparably cool and/or dry. In contrast, warm Dansgaard/Oeschger cycles were accompanied by wetter conditions. This is in agreement with previous evidence for the Holocene, when North Atlantic cold (warm) events coincided with drier (wetter) conditions in Cuba. However, our record suggests that this connection was less dominant during MIS 4 to 2, displayed by a weaker response of Cuban precipitation proxies to North Atlantic climatic shifts than during MIS 5 in particular. We hypothesize that this weaker connection was mediated by the southerly shifted ITCZ inducing a weakening of the northern branch of the Caribbean Low Level Jet which usually transports moisture into the northern Caribbean. This is strikingly evident during the deglacial, when driest and/or coolest conditions prevailed in western Cuba from HS 1 into the Younger Dryas, including the Bølling/Allerød interstadial. • We present a speleothem stable isotope and trace element record from Cuba covering the last 96 ka. • Our results confirm the link of Caribbean precipitation to NA climate, insolation and the AMOC. • Last glacial NA cold (warm) (inter)-stadials coincided with drier (wetter) conditions in Cuba. • During the LGM, our data suggest a shift to more abundant C4 vegetation and/or reduced soil activity. • We observe a weaker sensitivity to NA climate during MIS 4 to 2 compared to MIS5 and the Holocene. [ABSTRACT FROM AUTHOR]

The climate of the western Mediterranean was characterized by a strong precipitation gradient during the Holocene driven by atmospheric circulation patterns. The scarcity of terrestrial paleoclimate archives has precluded exploring this hydroclimate pattern during Marine Isotope Stages 5 to 3. Here we present stable carbon and oxygen isotope records from three flowstones from southeast Iberia, which show that Dansgaard/Oeschger events were associated with more humid conditions. This is in agreement with other records from the Iberian Peninsula, the Mediterranean, and western Europe, which all responded in a similar way to millennial‐scale climate variability in Greenland. This general increase in precipitation during Dansgaard/Oeschger events cannot be explained by any present‐day or Holocene winter atmospheric circulation pattern. Instead, we suggest that changes in sea surface temperature played a dominant role in determining precipitation amounts in the western Mediterranean. Plain Language Summary: Climate events characterized by a sudden temperature increase of up to 10 °C occurring in less than a few decades during the last glacial are recorded in Greenland ice cores. These abrupt warmings, the Dansgaard/Oeschger events, affected large regions of the Northern Hemisphere. The understanding of the regional response in precipitation during these climate shifts is limited for the western Mediterranean, due to the restricted number of terrestrial climate records that cover the last glacial period at sufficient resolution. Speleothems and their stable isotope compositions allow to trace changes in climate and vegetation based on an accurate chronological framework. Here we present a speleothem stable isotope record that shows that the Dansgaard/Oeschger events were associated with increased rainfall and a denser vegetation in the western Mediterranean. A similar pattern was observed for western Europe and other parts of the Mediterranean, and we propose that this was related to generally higher sea surface temperatures of the surrounding oceans rather than a reorganization of atmospheric circulation. Key Points: Western Mediterranean precipitation responded to Greenland interstadials and stadials in a coherent mannerDansgaard/Oeschger interstadials were accompanied by humid climate conditions over the western MediterraneanAtmospheric circulation patterns did not induce spatial differences in precipitation during the last glacial as they did during the Holocene [ABSTRACT FROM AUTHOR]

The cave bear was a prominent member of the Upper Pleistocene fauna in Eurasia. While breakthroughs were recently achieved with respect to its phylogeny using ancient DNA techniques, it is still challenging to date cave bear fossils beyond the radiocarbon age range. Without an accurate and precise chronological framework, however, key questions regarding the palaeoecology cannot be addressed, such as the extent to which large climate swings during the last glacial affected the habitat and possibly even conditioned the final extinction of this mammal. Key to constraining the age of cave bear fossils older than the lower limit of radiocarbon dating is to date interlayered speleothems using 230Th/U. Here we report new results from one such site in the Eastern European Alps (Schwabenreith Cave), which yielded the highest density of bones of cave bear (Ursus spelaeus eremus). Although dating of the flowstones overlying this fossiliferous succession was partly compromised by diagenetic alteration, the 230Th/U dates indicate that the bear hibernated in this cave after about 113 ka and before about 109 ka. This time interval coincides with the equivalent of Greenland Stadial 25, suggesting possible climate control on the cave bear's habitat and behaviour. © 2019 The Authors. Journal of Quaternary Science Published by John Wiley & Sons Ltd [ABSTRACT FROM AUTHOR]

Abstract Here we present novel cave-analogue experiments directly investigating stable carbon and oxygen isotope fractionation between the major involved species of the carbonate system (HCO 3 −, CO 2 , CaCO 3 and H 2 O). In these experiments, which were performed under controlled conditions inside a climate box, a thin film of solution flew down an inclined marble or glass plate. After different distances of flow and, thus, residence times on the plate, pH, electrical conductivity, supersaturation with respect to calcite, precipitation rate as well as the δ18O and δ13C values of the dissolved inorganic carbon (DIC) and the precipitated CaCO 3 were obtained. Progressive precipitation of CaCO 3 along the plate is accompanied by degassing of CO 2 and stable isotope fractionation, and the system is driven out of isotope equilibrium. We observe a strong enrichment of the δ13C values with increasing residence time and a smaller enrichment in δ18O. The temporal evolution of the δ18O and δ13C values of both the DIC and the precipitated CaCO 3 can be explained by a Rayleigh fractionation model, but the observed enrichment in δ13C values is much larger than expected based on isotope equilibrium fractionation factors. Our setup enables to determine the fractionation between CaCO 3 and HCO 3 −, i.e., ε CaCO3/HCO3−. Carbon isotope fractionation, 13ε CaCO3/HCO3− , is strongly negative for all experiments and much lower than equilibrium isotope fractionation (0–1‰). In addition, 13ε CaCO3/HCO3− decreases with increasing residence time on the plate, and thus decreasing supersaturation with respect to calcite. Thus, isotope fractionation depends on precipitation rate and consequently occurs under kinetic conditions. This is in contrast to previous studies, which found no rate-dependence and no or even a positive carbon isotope fractionation between CaCO 3 and HCO 3 −. Oxygen isotope fractionation, 18ε CaCO3/HCO3− , is also negative and dependent on precipitation rate. Since no literature values for 18ε CaCO3/HCO3− are available, we calculated 18ε CaCO3/HCO3− using equilibrium oxygen isotope fractionation factors between water and calcite and water and HCO 3 −, respectively. At the beginning of the plate, the fractionation is in agreement with the fractionation calculated using fractionation factors determined in cave systems. The observed fractionation between CaCO 3 and water, 1000ln18α, is also in good agreement with the values determined in cave systems and shows a very similar temperature dependence 1000 ln 18 α = 16.516 ± 1.267 ∗ 10 3 T − 26.141 ± 4.356. However, with progressive precipitation of CaCO 3 along the plate, the system is forced out of isotope equilibrium with the water, and 1000ln18α increases. The large, negative, rate-dependent isotope fractionations observed in this study suggest that precipitation of speleothem calcite is strongly kinetically controlled and may, thus, have a large effect on speleothem δ18O and δ13C values. Since these values may erroneously be interpreted as reflecting changes in past temperature, precipitation and/or vegetation density, these results have important implications for paleoclimate reconstructions from speleothems. [ABSTRACT FROM AUTHOR]

Their amenability to radiometric dating (U-series) makes speleothems (secondary cave carbonate deposits) a key archive of past climatic and environmental changes. However, incorporation of non-radiogenic thorium can hamper U-series dating, and samples older than ca. 600 ka remain out-of-reach for UTh dating. Our aim is to develop isothermal thermoluminescence (ITL) dating as an alternative approach for otherwise undatable samples. The calcite thermoluminescence (TL) signal (280 °C peak) saturates at very high doses (saturation dose up to 5000 Gy) [1,2], which shows great potential to extend the dating limit to several millions of years. However, a spurious TL signal occurring in the high temperature range so far hindered its application [3,4]. The conventional multiple-aliquot additive-dose (MAAD) protocol used for TL dating applies extrapolation for equivalent dose (De) estimation, which is also associated with large uncertainties. ITL dating with the single-aliquot regenerative-dose (SAR) protocol [5,6] might be a promising way to circumvent these issues as it reduces the influence of the spurious TL signal and it applies interpolation to obtain the De. However, this protocol has not been tested yet on samples with independent age control. Here we test the ITL SAR dating protocol on a speleothem sample from Bleßberg cave, Germany, which has been accurately dated by the 230Th/U-method (425.6±3.9 ka to 321.6±2.0 ka, based on 17 dates). An ITL measurement at 235 °C for 200 s can remove the 280 °C TL peak completely without TL contribution from the higher temperature range. The ITL De shows a plateau in the ITL temperature range between 230 °C and 240 °C. Peak shifting and isothermal annealing tests indicate that the 280 °C TL peak and the ITL signal at 235 °C have lifetimes of tens of millions of years at 10 °C, which is sufficiently stable considering the age range of this speleothem sample. The accurate alpha efficiency (a-value) and the U and Th distribution within the sample are measured to estimate the dose rate. The time-dependent dose rate variation due to U-series disequilibrium is corrected for. The ITL ages are compared with the 230Th/U ages to evaluate the performance of the ITL SAR dating protocol. [ABSTRACT FROM AUTHOR]

Speleothem stable carbon isotope (δ 13 C) records provide important paleoclimate and paleo-environmental information. However, the interpretation of these records in terms of past climate or environmental change remains challenging because of various processes affecting the δ 13 C signals. A process that has only been sparsely discussed so far is carbon isotope exchange between the gaseous CO 2 of the cave atmosphere and the dissolved inorganic carbon (DIC) contained in the thin solution film on the speleothem, which may be particularly important for strongly ventilated caves. Here we present a novel, complete reaction diffusion model describing carbon isotope exchange between gaseous CO 2 and the DIC in thin solution films. The model considers all parameters affecting carbon isotope exchange, such as diffusion into, out of and within the film, the chemical reactions occurring within the film as well as the dependence of diffusion and the reaction rates on isotopic mass and temperature. To verify the model, we conducted laboratory experiments under completely controlled, cave-analogue conditions at three different temperatures (10, 20, 30 °C). We exposed thin (≈0.1 mm) films of a NaHCO 3 solution with four different concentrations (1, 2, 5 and 10 mmol/l, respectively) to a nitrogen atmosphere containing a specific amount of CO 2 (1000 and 3000 ppmV). The experimentally observed temporal evolution of the pH and δ 13 C values of the DIC is in good agreement with the model predictions. The carbon isotope exchange times in our experiments range from ca. 200 to ca. 16,000 s and strongly depend on temperature, film thickness, atmospheric pCO 2 and the concentration of DIC. For low pCO 2 (between 500 and 1000 ppmV, as for strongly ventilated caves), our time constants are substantially lower than those derived in a previous study, suggesting a potentially stronger influence of carbon isotope exchange on speleothem δ 13 C values. However, this process should only have an influence in case of very long drip intervals and slow precipitation rates. [ABSTRACT FROM AUTHOR]

Here, we present high-resolution trace element and stable isotope records from three coeval Holocene stalagmites from the Herbstlabyrinth cave system, Central Germany. All stalagmites were precisely dated using MC-ICPMS 230Th/U-dating. One stalagmite started to grow at 13.62 ± 0.13 ka BP, covering the late Glacial; the other two speleothems started to grow at 11.13 ± 0.08 and 10.26 ± 0.08 ka BP, respectively. The combined record covers the entire Holocene. The interpretation of the different climate proxies is supported by data from a detailed cave monitoring programme. Cold conditions during the Younger Dryas are reflected by intermittent stalagmite growth at the Herbstlabyrinth. The δ18O records are in general agreement with the NGRIP δ18O record on millennial time scales indicating that speleothem δ18O values at the Herbstlabyrinth reflect large-scale climate variability in the North Atlantic area. The 8.2 ka event is clearly visible as a pronounced negative excursion in the δ18O records. In all other proxies, it is not reflected as a major excursion. Correlation and principal component analysis enable us to disentangle the various processes affecting the stable isotope and trace element signals. Phases with higher P, Ba and U concentrations and more negative δ13C values are interpreted as reflecting more productive vegetation above the cave. The negative correlation of Mg with P, Ba and U and the positive correlation with δ13C indicate more recharge during phases of more productive vegetation, probably because of increased rainfall. The majority of the observed phases of reduced vegetation productivity and drier climate coincide with cooler periods in the polar North Atlantic as reflected by a higher abundance of hematite-stained grains (i.e. the Bond events), suggesting a close relationship between terrestrial climate in Central Europe and the polar North Atlantic. [ABSTRACT FROM AUTHOR]

The connection between climatic change and social response is complex because change articulates a number of inter-related factors. Human decisions are filtered by social buffers – including social memory, risk perception, and cultural priorities – and the rate and scale of climate change is usually much larger than the scale of human decision-making. In this article, we provide information on climate change based on precisely dated speleothems with the response evident in archaeological sites that have radiocarbon date ranges within the same time frame. A stalagmite recovered from within the catchment area for aquifer recharge of the Pre-Arawak site of Angostura in Barceloneta, Puerto Rico, shows that a significant wet period occurred between 3.9 and 3.1 ka (primarily centered at 3.5 ka). We investigate the effect that this increase in precipitation had on the earliest occupations on the island in the context of palaeoenvironmental, geoarchaeological, and archaeological records from Angostura, Maruca, and Paso del Indio. Our analysis suggests the presence of two different adaptation strategies: settlement relocation and microlandscape modification. Our study concludes that the social response to change cannot be seen as monolithic given that human behavior, even within the same period, addresses the needs of individual groups with different priorities. This multiplicity of responses can indeed enhance resilience as social support can continue through alliances and exchanges, strengthening social bonds that can help buffer catastrophes. The results can help shed light on the range of adaptation strategies to change encompassed within the manifestations of social resilience or vulnerability. [ABSTRACT FROM PUBLISHER]

Speleothems can be precisely dated by U-series disequilibrium methods. One basic assumption of the 230 Th/U-dating method is that the system remains closed and U and Th isotopes are neither lost nor added after deposition. For stalagmites, this requirement is usually fulfilled due to their protected environment in caves. However, undersaturated drip water may lead to diagenesis of speleothem CaCO 3 and altered 230 Th/U-ages. Here we present a detailed petrographic investigation using thin sections and 230 Th/U-ages of a stalagmite from the Riesenberghöhle, northern Germany, which grew during Marine Isotope Stages 5e, c and a. The occurrence of a mosaic fabric in large parts of the stalagmite in combination with several age inversions is a clear indication for diagenetic alteration. We discuss the potential diagenetic processes and quantitatively model their influence on the 230 Th/U ages. Post-depositional U loss leads to increasing ( 230 Th/ 238 U) activity ratios and, thus, apparently older ages. In contrast, post-depositional addition of U results in decreased ( 230 Th/ 238 U) activity ratios and apparently younger ages. Comparison with our modelling results suggests that diagenesis occurred early after deposition. Initial and post-depositional detrital contamination probably played a minor role for the observed age inversions. [ABSTRACT FROM AUTHOR]

Cover Feature: Development of a Method for Anodic Degradation of Lignin for the Analysis of Paleo-Vegetation Proxies in Speleothems (ChemElectroChem 6/2022) Anode, Electrochemistry, Lignin, Oxidation, Speleothem Keywords: Anode; Electrochemistry; Lignin; Oxidation; Speleothem EN Anode Electrochemistry Lignin Oxidation Speleothem 1 1 1 03/31/22 20220329 NES 220329 B The Cover Feature b illustrates the pathway of lignin from the plant into a stalagmite and to the electrochemically generated monomeric analytes. [Extracted from the article]

Abstract: We present a speleothem stable oxygen isotope record for the last 12.5ka based on two stalagmites from western Cuba. The δ 18O signal is interpreted to represent past precipitation variability. Both stalagmites show a pronounced transition from higher δ 18O values (indicating drier conditions) to more negative δ 18O values (suggesting wetter conditions) between 10 and 6ka. This transition is also visible in a planktonic δ 18O record off Haiti. On orbital timescales, the δ 18O value of Caribbean precipitation, thus, strongly resembles the oxygen isotope composition of Caribbean surface water. On millenial timescales, the speleothem δ 18O record shows a high correlation to a North Atlantic sea surface temperature (SST) record off West Africa as well as a similarity with the Bond events. Periods of lower North Atlantic SST correspond to less precipitation in the Caribbean and vice versa. The potential teleconnection to the Caribbean may reflect the position of the Intertropical Convergence Zone because a further southward position of the ITCZ leads to reduced precipitation in the northern Caribbean. [Copyright &y& Elsevier]

Abstract: Speleothems, such as stalagmites and flowstones, can be dated with unprecedented precision in the range of the last 650,000 a by the 230Th/U-method, which is considered as one of their major advantages as climate archives. However, a standard approach for the construction of speleothem age models and the estimation of the corresponding uncertainty has not been established yet. Here we apply five age modelling approaches (StalAge, OxCal, a finite positive growth rate model and two spline-based models) to a synthetic speleothem growth model and two natural samples. All data sets contain problematic features such as outliers, age inversions, large and abrupt changes in growth rate as well as hiatuses. For data sets constrained by a large number of ages and not including problematic sections, all age models provide similar results. In case of problematic sections, the algorithms provide significantly different age models and uncertainty ranges. StalAge, OxCal and the finite positive growth rate model are, in general, more flexible since they are capable of modelling hiatuses and account for problematic sections by increased uncertainty. The spline-based age models, in contrast, reveal problems in modelling problematic sections. Application to the synthetic data set allows testing the performance of the algorithms because the ‘true’ age model is available and can be compared with the age models. OxCal and StalAge generally show a good performance for this example, even if they are inaccurate for a short section in the area of a hiatus. The two spline-based models and the finite positive growth rate model show larger inaccurately modelled sections. [Copyright &y& Elsevier]

Abstract: The high spatial resolution of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) microanalysis of speleothems and biogenic calcium carbonates makes it possible to improve our understanding of past climatic conditions. However, there are analytical problems associated with this method, such as molecular interferences, elemental fractionation, and mass-load-dependent matrix effects, when using NIST silicate reference glasses for calibration. Our study with a sector-field ICP-MS shows that many masses are affected by interferences, such as 24Mg+ by 48Ca++ or 31P+ by 15N16O+. Elemental fractionation and mass-load-dependent matrix effects have been detected for both 213 and 193nm Nd:YAG lasers. They are small for refractory lithophile elements, in particular for the 193nm laser (<5%). For chalcophile/siderophile trace elements with low boiling points, however, these effects are large (up to 40% and 20% for the 213 and 193nm lasers, respectively), and variable for the NIST glasses and carbonates. In this paper, a protocol for precise and accurate LA-ICP-MS analysis of calcium carbonates is established. Isotopes for interference-free measurements at low (M/ΔM ~300) and medium (M/ΔM ~4000) mass resolution have been identified. The NIST glasses are suitable for calibration of refractory lithophile element concentrations. However, matrix-matched calibration with carbonate reference materials, such as USGS MACS-1 or MACS-3, is necessary for accurate analysis of chalcophile/siderophile elements with low boiling points. Analytical reproducibility (RSD) is a factor of ~2 better using the 193nm laser than the 213nm laser. As shown by the analysis of MACS-1 and MACS-3, LA-ICP-MS analyses yield results that agree with the reference values within relative uncertainties of ca. 5–10% at the 95% confidence level. We have applied LA-ICP-MS for the determination of trace element concentrations in calcite and aragonite layers of a stalagmite and found large variations for Mg, Zn, Sr, and U. In ostracod shells, the concentrations of some trace elements (e.g., Sr and Ba) vary significantly, indicating the potential for paleoclimate research. [Copyright &y& Elsevier]

Abstract: Here we present a new algorithm (StalAge), which is designed to construct speleothem age models. The algorithm uses U-series ages and their corresponding age uncertainty for modelling and also includes stratigraphic information in order to further constrain and improve the age model. StalAge is applicable to problematic datasets that include outliers, age inversions, hiatuses and large changes in growth rate. Manual selection of potentially inaccurate ages prior to application is not required. StalAge can be applied by the general, non-expert user and has no adjustable free parameters. This offers the highest degree of reproducibility and comparability of speleothem records from different studies. StalAge consists of three major steps. Firstly, major outliers are identified. Secondly, age data are screened for minor outliers and age inversions, and the uncertainty of potential outliers is increased using an iterative procedure. Finally, the age model and corresponding 95%-confidence limits are calculated by a Monte-Carlo simulation fitting ensembles of straight lines to sub-sets of the age data. We apply StalAge to a synthetic stalagmite ’sample’ including several problematic features in order to test its performance and robustness. The true age is mostly within the 95%-confidence age limits of StalAge showing that the calculated age models are accurate even for very difficult samples. We also apply StalAge to three published speleothem datasets. One of those is annually laminated, and the lamina counting chronology agrees with the age model calculated by StalAge. For the other two speleothems the resulting age models are similar to the published age models, which are both based on smoothing splines. Calculated uncertainties are in the range of those calculated by combined application of Bayesian chronological ordering and a spline, showing that StalAge is efficient in using stratigraphic information in order to reduce age model uncertainty. The algorithm is written in the open source statistical software R and available from the authors or as an electronic supplement of this paper. [Copyright &y& Elsevier]

Abstract: Here we present the first U-series dated stable oxygen isotope record in continental Europe that covers the entire tripartite Penultimate Interglacial, i.e. Marine Isotope Stages 7.5 to 7.1. This record was obtained from a U-rich stalagmite from Spannagel Cave in the Austrian Alps which is largely devoid of kinetic isotope fractionation effects which comprised previously studied flowstone from this site. Composed of dense, columnar calcite this speleothem apparently grew without significant interruption for ca. 50 ka, albeit at a very slow rate. The age model was established based on 23 individual U/Th TIMS dates using a combination of a Bayesian approach, which includes additional information using stratigraphic constraints, and the mixed-effect regression model. The resulting record shows three prominent maxima in δ18O (MIS 7.5, 7.3 and 7.1) separated by a long earlier and a shorter later cold period (MIS 7.4 and 7.2, respectively). The mid points of the transitions into the three warm phases occurred at 240±3, 215±2 and 200±3 ka and the MIS 7/6 transition was dated to 190±3 ka. The timing of these climate transitions is supported by other samples from the same cave and agrees within analytical uncertainties with U/Th-dated evidence from corals, marine aragonitic sediments and submerged stalagmites, as well as with orbitally tuned deep-sea records. Good agreement was also found with new speleothem data from China as far as MIS 7.1 and 7.5 are concerned, whereas MIS 7.3 apparently started earlier and MIS 7.2 lasted longer than in the Alps. Comparing the European speleothem data with Antarctic ice cores reveals obvious differences in age (the latter suggesting an earlier start and a generally shorter duration of the three warm episodes). In essence, this study underscores the great potential of speleothems as accurate and precise chronometers of Pleistocene climate change and emphasizes the need for similar studies in other continents (including submerged caves) in order to improve the imperfect chronological framework of MIS 7. [Copyright &y& Elsevier]

Here we present clumped isotope Δ 47 data of cave analogous experiments. We investigate the evolution of the Δ 47 values of both the dissolved inorganic carbon (DIC) and the CaCO 3 of thin-films flowing down in channels along inclined marble and glass plates precipitating CaCO 3 along the flow path. With increasing distance of flow and residence time on the plate, we observe large deviations from the initial Δ 47 values, along with increasingly over-estimated apparent Δ 47 - temperatures derived from the precipitated CaCO 3. With further increasing residence time on the plates (>250 s) and decreasing supersaturation with respect to calcite, the CaCO 3 Δ 47 values start to approach the initial equilibrium values again. This highlights the potentially strong effect of disequilibrium isotope effects on clumped isotope temperatures derived from speleothems, in particular because the disequilibrium effect on the Δ 47 values is most pronounced in the first few 100 seconds of CaCO 3 precipitation. The experimental Δ 47 values are consistent with a recent modeling study by Guo and Zhou (2019). The maximum degree of disequilibrium, however, seems to be more pronounced than predicted by the model for some of the experiments. A potential reason for this observation is that suitable kinetic fractionation factors are so far not available. While the Δ 47 values of the CaCO 3 decrease along the plate as the model suggests for the Δ 47 values of the HCO 3 −, those of the DIC increase and follow the modelled Δ 47 values of the dissolved CO 2. Based on our study, we can neither confirm nor exclude a temperature dependence of the Δ 47 -δ18O slope as well as a dependence on cave pCO 2 , which highlights the complexity of this relationship. In addition, the non-linear evolution of Δ 47 and δ18O values with time and along the flow path restricts a correction of the Δ 47 and δ18O values based on the Δ 47 -δ18O slope to the initial phase of the isotope evolution. So far, a correction of the kinetic isotope effects is not yet possible, but this might be important in future studies if the disequilibrium slope on a Δ 47 -δ18O diagram could be precisely determined for the initial phase of isotope evolution. [ABSTRACT FROM AUTHOR]

Abstract Central European climate is strongly influenced by North Atlantic (Westerlies) and Siberian High circulation patterns, which govern precipitation and temperature dynamics and induce heterogeneous climatic conditions, with distinct boundaries between climate zones. These climate boundaries are not stationary and shift geographically, depending on long-term atmospheric conditions. So far, little is known about past shifts of these climate boundaries and the local to regional environmental response prior to the instrumental era. High resolution multi-proxy data (stable oxygen and carbon isotope ratios, S/Ca and Sr/Ca) from two Holocene stalagmites from Bleßberg Cave (Thuringia) are used here to differentiate local and pan-regional environmental and climatic conditions Central Germany through the Holocene. Carbon isotope and S/Ca and Sr/Ca ratios inform us on local Holocene environmental changes in and around the cave, while δ18O (when combined with independent records) serves as proxy for (pan-)regional atmospheric conditions. The stable carbon isotope record suggests repeated changes in vegetation density (open vs. dense forest), and increasing forest cover in the late Holocene. Concurrently, decreasing S/Ca values indicate more effective sulfur retention in better developed soils, with a stabilization in the mid-Holocene. This goes in hand with changes in effective summer infiltration, reflected in the Sr/Ca profile. Highest Sr/Ca values between 4 ka and 1 ka BP indicate intensified prior calcite precipitation resulting from reduced effective moisture supply. The region of Bleßberg Cave is sensitive to shifts of the boundary between maritime (Cfb) and continental (Dfb) climate and ideally suited to reconstruct past meridional shifts of this divide. We combined the Bleßberg Cave δ18O time series with δ18O data from Bunker Cave (western Germany) and a North Atlantic Oscillation (NAO) record from lake SS1220 (SW Greenland) to reconstruct the mean position of the Cfb-Dfb climate boundary. We further estimate the dynamic interplay of the North Atlantic Oscillation and the Siberian High and their influence on Central European climate. Repeated shifts of the Cfb-Dfb boundary over the last 4000 years might explain previously observed discrepancies between proxy records from Europe. Detailed correlation analyses reveal multi-centennial scale alternations of maritime and continental climate and, concurrently, waning and waxing influences of Siberian High and NAO on Central Europe. Highlights • U-series dated multi-proxy speleothem data from Bleßberg Cave, Thuringia cover the Holocene. • Local and pan-regional environmental and climatic changes are reconstructed. • Bleßberg Cave record is compared to data from W Germany and Greenland to infer maritime/continental climate regimes. • Waning/waxing of NAO and Siberian High influence on European climate is discussed for the last 4,000 years. [ABSTRACT FROM AUTHOR]

We present the first high-resolution trace element (Mg/Ca, Sr/Ca, Ba/Ca) record from a stalagmite in southwestern Romania covering the last 3.6 ka, which provides the potential for quantitative climate reconstruction. Precise age control is based on three independent dating methods, in particular for the last 250 yr, where chemical lamina counting is combined with the identification of the 20th century radiocarbon bomb peak and 230 Th/U dating. Long-term cave monitoring and model simulations of drip water and speleothem elemental variability indicate that precipitation-related processes are the main drivers of speleothem Mg/Ca ratios. Calibration against instrumental climate data shows a significant anti-correlation of speleothem Mg/Ca ratios with autumn/winter (October to March) precipitation (r = −0.61, p < 0.01), which is statistically robust when considering age uncertainties and auto-correlation. This relationship is used to develop a quantitative reconstruction of autumn/winter precipitation. During the late Holocene, our data suggest a heterogeneous pattern of past regional winter hydroclimate in the Carpathian/Balkan realm, along with intermittent weakening of the dominant influence of North Atlantic forcing. In agreement with other regional paleo-hydrological reconstructions, the observed variability reveals periodically occurring strong NW–SE hydro-climate gradients. We hypothesize, that this pattern is caused by shifts of the eastern edge of the area of influence of the NAO across central-eastern Europe due to the confluence of North Atlantic forcing, and other climatic features such as the East Atlantic/Western Russia (EAWR) pattern. [ABSTRACT FROM AUTHOR]

Speleothems are well established climate archives. A wide array of geochemical proxies, including stable isotopes and trace elements are present within speleothems to reconstruct past climate variability. However, each proxy is influenced by multiple factors, often hampering robust interpretation. Sr isotope ratios ( 87 Sr/ 86 Sr) can provide useful information about water residence time and water mixing in the host rock, as they are not fractionated during calcite precipitation. Laser ablation multi-collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has rarely been used for determination of Sr isotope signatures in speleothems, as speleothems often do not possess appropriately high concentrations of Sr to facilitate this analysis. Yet the advantages of this approach include rapid data acquisition, higher spatial resolution, larger sample throughput and the absence of chemical treatment prior to analysis. We present LA-MC-ICP-MS Sr isotope data from two speleothems from Morocco (Grotte de Piste) and India (Mawmluh Cave), and we compare linescan and spot analysis ablation techniques along speleothem growth axes. The analytical uncertainty of our LA-MC-ICP-MS Sr data is comparable to studies conducted on other carbonate materials. The results of both ablation techniques are reproducible within analytical error, implying that this technique yields robust results when applied to speleothems. In addition, several comparative measurements of different carbonate reference materials (i.e. MACS-3, JCt-1, JCp-1), including tests with standard bracketing and comparison of the 87 Sr/ 86 Sr ratios with a nanosecond laser ablation system and a state-of-the-art femtosecond laser ablation system, highlight the robustness of the method. [ABSTRACT FROM AUTHOR]

Aragonitic speleothems are increasingly utilised as palaeoclimate archives due to their amenability to high precision U–Th dating. Proxy records from fast-growing aragonitic stalagmites, precisely dated to annual timescales, can allow investigation of climatic events occurring on annual or even sub-annual timescales with minimal chronological uncertainty. However, the behaviour of many trace elements, such as uranium, in aragonitic speleothems has not thus far been as well constrained as in calcitic speleothems. Here, we use uranium concentration shifts measured across primary calcite-to-aragonite mineralogical transitions in speleothems to calculate the distribution coefficient of uranium in aragonitic speleothems (derived D U = 3.74 ± 1.13). Because our calculated D U is considerably above 1 increased prior aragonite precipitation due to increased karst water residence time should strongly control stalagmite aragonite U/Ca values. Consequently, uranium concentrations in aragonitic speleothems should act as excellent proxies for effective rainfall. We test this using a high-resolution ICP-MS derived trace element dataset from a Belizean stalagmite. YOK-G is an aragonitic stalagmite from Yok Balum cave in Belize with an extremely robust monthly-resolved chronology built using annual δ 13 C cycles. We interpret seasonal U/Ca variations in YOK-G as reflecting changes in the amount and seasonality of prior aragonite precipitation driven by variable rainfall amounts. The U/Ca record strongly suggests that modern drying has occurred in Belize, and that this drying was primarily caused by a reduction in wet season rainfall. This is consistent with published stable isotope data from YOK-G also very strongly suggesting modern rainfall reductions, previously interpreted as the result of southward ITCZ displacement. Our results strongly suggest that U/Ca values in aragonitic speleothems are excellent proxies for rainfall variability. This new tool, combined with the exceptional chronological control characteristic of aragonitic stalagmites and the high spatial resolution afforded by modern microanalytical techniques, should facilitate the construction of new exquisitely resolved rainfall records, providing rare insights into seasonality changes as well as long-term changes in local recharge conditions. [ABSTRACT FROM AUTHOR]

Spectacular geomorphic evidence of recent tectonic activity and three potentially strong prehistoric earthquakes were discovered in Obir Caves in the Karawanken Mountains. This paper presents active fault structures, geomorphic features, and the age constraints attributed to particular seismotectonic events. The 1976 Mw 6.7 Friuli earthquake about 100 km from Obir Caves caused only local speleothem damage. The 100 km hypocentral distance enabled attenuation of the seismic waves so speleothem damage due to stalagmite resonance frequency was dampened. The documented dripstone column damage was rather caused by its sudden shortening due to passing elastic S-waves with estimated 3.5 (+8.2/−1.5) mm PGD amplitudes. At least three distinct seismotectonic events in the Late Pleistocene and Early to Middle Holocene were constrained by radiometric dating. The 40.6 cm sinistral fault slip occurred between 41.8 ± 1.3 ka and 18.7 ± 0.4 ka ago, the 2.6 cm dextral oblique reverse fault slip happened between 10.73 ± 0.23 and 8.61 ± 0.15 ka ago, and another speleothem damage event took place between 6.28 ± 0.24 ka and 5.7 ± 1.2 ka ago. These events were most probably accompanied by distinct destructive to very destructive paleoearthquakes with local intensities ranging from VIII to X on the ESI 2007 scale, significant rock weakening, and forming the large deep-seated gravitational slope deformation on the southeastern mountain slopes adjacent to Obir Caves. • We discovered evidence of three paleoearthquakes in the Eastern Alps. • Speleothem damage and fault offsets indicate intensities VIII to X (ESI 2007). • They occurred in the Late Pleistocene and Early to Middle Holocene. • 1976 Mw 6.7 Friuli EQ caused dripstone column damage by its co-seismic shortening. [ABSTRACT FROM AUTHOR]

Structural mapping and dating of damaged speleothems have been used to investigate earthquake records in caves, especially of large infrequent events. However, there are few reports of damages in caves visited before and after a particular earthquake, where the damage can be directly related to a recorded event. We mapped the previously unexplored Korakia Cave on Pserimos island in the Dodecanese (Greece) prior to the 2017 M w 6.6 Bodrum–Kos earthquake. The Dodecanese is at the transition between the Aegean and Anatolian region and is known for its strong seismicity. Although several hundred stalactites with large height-to-width ratios are preserved on the roof of Korakia Cave, the cave has an extensive record of damaged speleothems, which have been caused by movements along normal faults. Here we present new data and 230Th/U-ages of paleoseismic events that are partly older than the limit of the dating method. A cave visit after the 2017 M w 6.6 Bodrum–Kos earthquake revealed that c. 10 cm small stalactites, which were actively growing along fractures in the cave ceiling, had been chipped off by movements along the fractures during that earthquake. We conclude that movements along fractures or faults during seismic events can easily damage stalagmites and stalactites. However, damage related to the resonance frequency of the dripstones matching with the seismic wave frequency, which has been suggested to break dripstones with large height-to-width ratios, was not observed in Korakia Cave. • We document severe speleothem damage in a cave in the Dodecanese. • Speleothem damage is directly related to movement along normal faults. • Hundreds of fragile stalactites unrelated to faulting are undamaged. • Stalactites chipped off during the 2017 M w 6.6 Bodrum-Kos earthquake. [ABSTRACT FROM AUTHOR]