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Hai Cheng - One of the best experts on this subject based on the ideXlab platform.
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relationship between the asian summer monsoon circulation and Speleothem δ18o of xiaobailong cave
Climate Dynamics, 2019Co-Authors: Yu Yang, Hai Cheng, Ruowen Yang, Jie Cao, Jingyao Zhao, Jian WangAbstract:The negative correlation between the local precipitation and Speleothem $$ \delta^{18} {\text{O}} $$ is used extensively in the study of monsoon variability. However, the correlation coefficient between them do not always pass the significance test, which makes it difficult to interpret the monsoon variability using Speleothem $$ \delta^{18} {\text{O}} $$ . In this study, regression analysis and corresponding significance test method are employed to investigate the relationship between the Asian summer monsoon circulation and Speleothem $$ \delta^{18} {\text{O}} $$ of Xiaobailong cave using CERA-20C, Speleothem $$ \delta^{18} {\text{O}} $$ of Xiaobailong cave, and precipitation and temperature data from 8 meteorological stations around the cave. Diagnostic results indicate that the Speleothem $$ \delta^{18} {\text{O}} $$ of Xiaobailong cave can reflect the variability of Asian summer monsoon circulation via the rainout effect from the nearest upstream sources to destination. The stronger (weaker) ASM circulation causes isotopically depleted (enriched) water vapor via enhancing (reducing) the Rayleigh distillation processes during the transport of water vapor from the northern Bay of Bengal and the northern South China Sea to the region around the cave. The lower (higher) isotope value in water vapor further leads to depleted (enriched) Speleothem $$ \delta^{18} {\text{O}} $$ of Xiaobailong cave. The numerical experiments using isotope-incorporated spectral model substantiate the key physical process revealed in the observational analysis. These results provide an efficient way for reconstructing the paleomonsoon circulation with $$ \delta^{18} {\text{O}} $$ in Speleothems, ice cores, and tree ring cellulose.
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assessing the dead carbon proportion of a modern Speleothem from central brazil
Quaternary Geochronology, 2019Co-Authors: Kita Macario, Hai Cheng, Francisco W Cruz, Valdir F Novello, Nicolas M Strikis, Izabela Hammerschlag, Eduardo Q Alves, Larry Edwards, Fabio Ramos Dias De AndradeAbstract:Abstract Geographic and temporal variations in atmospheric carbon isotopic ratios are recorded in environmental proxies. In temperate regions, this may assist in the construction of datasets for the calibration of radiocarbon ages. Over the tropics, the high growth rate of Speleothems combined with high precision 230Th dating provides potential records for atmospheric 14C reconstruction. In this preliminary work, we investigate the isotopic composition (δ18O and δ13C) of a Speleothem from central Brazil, precisely dated by the multi-collector inductively coupled plasma mass spectrometry technique (MC-ICP-MS). Radiocarbon Accelerator Mass Spectrometry (AMS) measurements were compared to the 14C concentration in the atmosphere during the nuclear tests period based on the Bomb13SH1-2 curve. Our results show that the Speleothem dead carbon proportion is less than 20% between 1932 and 1992 AD while δ13C values vary between −14 and −9‰. Given that the empirical radiocarbon calibration curves for the Southern Hemisphere were constructed based on limited records, we discuss the potential and limitations of Brazilian Speleothems for the evaluation of atmospheric 14C concentrations over the last millennia.
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ion microprobe δ18o analyses to calibrate slow growth rate Speleothem records with regional δ18o records of precipitation
Earth and Planetary Science Letters, 2018Co-Authors: David Dominguezvillar, Kristina Krklec, Lawrence R. Edwards, Sonja Lojen, Reinhard Kozdon, Hai ChengAbstract:Abstract Paleoclimate reconstructions based on Speleothems require a robust interpretation of their proxies. Detailed transfer functions of external signals to the Speleothem can be obtained using models supported by monitoring data. However, the transferred signal may not be stationary due to complexity of karst processes. Therefore, robust interpretations require the calibration of Speleothem records with instrumental time series lasting no less than a decade. We present the calibration of a Speleothem δ 18 O record from Postojna Cave (Slovenia) with the regional record of δ 18 O composition of precipitation during the last decades. Using local meteorological data and a regional δ 18 O record of precipitation, we developed a model that reproduces the cave drip water δ 18 O signal measured during a two-year period. The model suggests that the average water mixing and transit time in the studied aquifer is 11 months. Additionally, we used an ion microprobe to study the δ 18 O record of the top 500 μm of a Speleothem from the studied cave gallery. According to U–Th dates and 14C analyses, the uppermost section of the Speleothem was formed during the last decades. The δ 18 O record of the top 500 μm of the Speleothem has a significant correlation ( r 2 = 0.64 ; p-value δ 18 O record of cave drip water. Therefore, we confirm that the top 500 μm of the Speleothem grew between the years 1984 and 2003 and that the Speleothem accurately recorded the variability of the δ 18 O values of regional precipitation filtered by the aquifer. We show that the recorded Speleothem δ 18 O signal is not seasonally biased and that the hydrological dynamics described during monitoring period were stationary during recent decades. This research demonstrates that Speleothems with growth rates
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Geochemistry of Speleothems affected by aragonite to calcite recrystallization – Potential inheritance from the precursor mineral
Geochimica et Cosmochimica Acta, 2017Co-Authors: David Domínguez-villar, Hai Cheng, Kristina Krklec, Primož Pelicon, Ian J. Fairchild, Lawrence R. EdwardsAbstract:Abstract Formerly aragonite Speleothems recrystallized to calcite result from solutions subsaturated in aragonite and supersaturated in calcite that infiltrate into the Speleothem through the interconnected porosity. In most cases, the crystal replacement takes place through a thin solution film. This diagenetic process can occur under open or semi-closed geochemical conditions. Thus, secondary calcite crystals record the composition of the fluid at the time of diagenesis affected by calcite partition coefficients and fractionation factors (open system) or partly inherit the composition of the primary aragonite (semi-closed system). So, whether or not recrystallized aragonite Speleothems can record reliable geochemical signals from the time of Speleothem primary deposition still is an open debate. We studied a stalagmite from Eagle Cave (Spain) predominantly composed of secondary calcite that replaced aragonite, although a core of primary aragonite extending 45 mm along the growth direction was preserved at the base of the sample. We obtained Mg and Sr compositional maps, paired U–Th dating and δ 18 O and δ 13 C profiles across the diagenetic front. Additionally, two parallel isotope records were obtained along the Speleothem growth direction in the aragonite and calcite sectors. Our results support that recrystallization of this Speleothem took place in open system conditions for δ 18 O, δ 13 C, Mg and Sr, but in semi-closed system conditions for U and Th. The recrystallization of this sample took place during one or several events, likely after the Younger Dryas as a result of climate change influencing drip water composition. Based on compositional zoned patterns, we suggest that the advance of diagenetic fronts in this Speleothem had an average rate of 50 ± 45 μm/yr. Such recrystallization rate can transform any aragonite Speleothem into calcite within a few centuries. We suggest that the volume of water interacting with the Speleothem at the time of recrystallization is of critical importance for inheritance of different elements. The volume of solution is controlled by (1) the discharge of water passing through the sample and (2) the lapse time between aragonite dissolution and calcite precipitation. Hydrology and hydrochemistry of the interacting solution, together with the mineralogy and texture of the Speleothem are the essential controls for the diagenesis of the Speleothem. Recrystallization of aragonite Speleothems does not follow stratigraphical levels of the sample but occurs along sites with preferential flow paths in any sector of the Speleothem. In these cases the relationship between age and distance from base is not preserved. However, alternation of periods of recrystallization with periods of aragonite precipitation causing Speleothem accretion can result in recrystallized Speleothems with coherent distance from the base-age relationship. Thus, early diagenesis of Speleothems affected by seasonal or inter-annual oscillation of drip waters supersaturated and subsaturated in aragonite may provide best-scenario conditions for dating and preservation of paleoenvironmental records along recrystallized Speleothems. However, even in this scenario, the variable discharge and the diagenetic rate control the geochemical inheritance from the primary aragonite crystals.
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determination of aragonite trace element distribution coefficients from Speleothem calcite aragonite transitions
Geochimica et Cosmochimica Acta, 2016Co-Authors: Jasper A Wassenburg, Hai Cheng, Jessica L. Oster, Denis Scholz, Klaus Peter Jochum, Adrian Immenhauser, Detlev K Richter, Tobias Hager, Robert A Jamieson, James U L BaldiniAbstract:The processes that govern the incorporation of (trace) elements into Speleothems can often be linked to environmental changes. Although element incorporation into Speleothem calcite is now reasonably well understood, current knowledge regarding trace element variability in Speleothem aragonite is very limited. Of particular interest is whether trace element distribution coefficients are above or below one in order to assess the extent to which prior aragonite precipitation has affected Speleothem aragonite trace element records. This study uses nine calcite-to-aragonite transitions in seven Speleothems from diverse environmental settings to derive the first quantitative estimates of the distribution coefficients for several elements in Speleothem aragonite: DMg(Ar) = 9.7E−5 ± 9.01E−5, DBa(Ar) = 0.91 ± 0.88, DSr(Ar) = 1.38 ± 0.53, and DU(Ar) = 6.26 ± 4.54 (1σ SD). For one Speleothem from western Germany, the distribution coefficients are generally higher, which is potentially related to the very low growth rates (<11 μm/year) of this sample. In particular, DSr(Ar) appears to show a negative correlation with growth rate when growth rate is below 20 μm/year. In summary, our results demonstrate that Speleothem aragonite DMg(Ar) is below one, DU(Ar) is considerably above one, and DSr(Ar) is above one or close to unity. For DBa(Ar), reaching a similar conclusion is difficult due to the relatively high uncertainty. Enhanced prior aragonite precipitation will thus result in lower U and higher Mg concentrations in Speleothem aragonite, although in many cases Mg in Speleothem aragonite is most likely dominated by other processes. This result suggests that U concentrations in aragonitic stalagmites could serve as a very effective proxy for palaeo-rainfall.
Stef Vansteenberge - One of the best experts on this subject based on the ideXlab platform.
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characterizing the eemian weichselian transition in northwestern europe with three multiproxy Speleothem archives from the belgian han sur lesse and remouchamps cave systems
Quaternary Science Reviews, 2019Co-Authors: Stef Vansteenberge, Sophie Verheyden, David P Gillikin, Dominique Genty, Dominique Blamart, Steven Goderis, Stijn Van Malderen, Frank Vanhaecke, Florent Hodel, Yves QuinifAbstract:Abstract Interglacial to glacial transitions represent the most drastic turnovers in the Quaternary climate system. Yet, millennial-scaled climate variability and stochastic internal variability that result in (inter)glacial transitions remain poorly understood. Here, three Speleothems from two different cave systems in Belgium are investigated to characterize the Eemian to early Weichselian transition. The Speleothems show high reproducibility for δ13C, interpreted as a proxy for past vegetation activity, controlled by type of vegetation above the cave. All three Speleothems show a drastic increase in δ13C between 118 and 117 ka, reflecting a rapid change in vegetation from last interglacial temperate tree species towards glacial open-grass vegetation. This transition shows a strong affinity with the Late Eemian Aridity Pulse (LEAP) at 118 ± 1 ka, previously identified in pollen records from Western Germany. An age of 117.7 ± 0.5 ka is determined for the start of this transition in the Belgian Speleothems. The Speleothem records show a distinct transition in the proxies between Eemian optimum conditions and increased variability during the glacial inception and therefore the Eemian-Weichselian transition is set at 117.7 ± 0.5 ka in the Speleothem records. High-resolution trace element analysis shows that the transition is initiated by a cooling pulse followed by a decrease in precipitation. Through comparison with other archives, including North-Atlantic sedimentary records, it is proposed that the transition at 117.7 ka constitutes an internal climate response caused by a substantial input of freshwater from degraded ice-sheets by the end of the Eemian (∼120-118 ka).
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paleoclimate in continental northwestern europe during the eemian and earlyweichselian 125 97 ka insights from a belgian Speleothem
Climate of The Past, 2016Co-Authors: Stef Vansteenberge, Hai Cheng, Lawrence R. Edwards, Sophie Verheyden, Eddy Keppens, Philippe ClaeysAbstract:Abstract. The last interglacial serves as an excellent time interval for studying climate dynamics during past warm periods. Speleothems have been successfully used for reconstructing the paleoclimate of last interglacial continental Europe. However, all previously investigated Speleothems are restricted to southern Europe or the Alps, leaving large parts of northwestern Europe undocumented. To better understand regional climate changes over the past, a larger spatial coverage of European last interglacial continental records is essential, and Speleothems, because of their ability to obtain excellent chronologies, can provide a major contribution. Here, we present new, high-resolution data from a stalagmite (Han-9) obtained from the Han-sur-Lesse Cave in Belgium. Han-9 formed between 125.3 and ∼ 97 ka, with interruptions of growth occurring at 117.3–112.9 and 106.6–103.6 ka. The Speleothem was investigated for its growth, morphology and stable isotope (δ13C and δ18O) composition. The Speleothem started growing relatively late within the last interglacial, at 125.3 ka, as other European continental archives suggest that Eemian optimum conditions were already present during that time. It appears that the initiation of Han-9 growth is caused by an increase in moisture availability, linked to wetter conditions around 125.3 ka. The δ13C and δ18O proxies indicate a period of relatively stable conditions after 125.3 ka; however, at 120 ka the Speleothem δ18O registered the first signs of regionally changing climate conditions, being a modification of ocean source δ18O linked to an increase in ice volume towards the Marine Isotope Stage (MIS) 5e–5d transition. At 117.5 ka, drastic vegetation changes are recorded by Han-9 δ13C immediately followed by a cessation of Speleothem growth at 117.3 ka, suggesting a transition to significantly dryer conditions. The Han-9 record covering the early Weichselian displays larger amplitudes in both isotope proxies and changes in stalagmite morphology, evidencing increased variability compared to the Eemian. Stadials that appear to be analogous to those in Greenland are recognized in Han-9, and the chronology is consistent with other European (Speleothem) records. Greenland Stadial 25 is reflected as a cold/dry period within Han-9 stable isotope proxies, and the second interruption in Speleothem growth occurs simultaneously with Greenland Stadial 24.
Sophie Verheyden - One of the best experts on this subject based on the ideXlab platform.
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characterizing the eemian weichselian transition in northwestern europe with three multiproxy Speleothem archives from the belgian han sur lesse and remouchamps cave systems
Quaternary Science Reviews, 2019Co-Authors: Stef Vansteenberge, Sophie Verheyden, David P Gillikin, Dominique Genty, Dominique Blamart, Steven Goderis, Stijn Van Malderen, Frank Vanhaecke, Florent Hodel, Yves QuinifAbstract:Abstract Interglacial to glacial transitions represent the most drastic turnovers in the Quaternary climate system. Yet, millennial-scaled climate variability and stochastic internal variability that result in (inter)glacial transitions remain poorly understood. Here, three Speleothems from two different cave systems in Belgium are investigated to characterize the Eemian to early Weichselian transition. The Speleothems show high reproducibility for δ13C, interpreted as a proxy for past vegetation activity, controlled by type of vegetation above the cave. All three Speleothems show a drastic increase in δ13C between 118 and 117 ka, reflecting a rapid change in vegetation from last interglacial temperate tree species towards glacial open-grass vegetation. This transition shows a strong affinity with the Late Eemian Aridity Pulse (LEAP) at 118 ± 1 ka, previously identified in pollen records from Western Germany. An age of 117.7 ± 0.5 ka is determined for the start of this transition in the Belgian Speleothems. The Speleothem records show a distinct transition in the proxies between Eemian optimum conditions and increased variability during the glacial inception and therefore the Eemian-Weichselian transition is set at 117.7 ± 0.5 ka in the Speleothem records. High-resolution trace element analysis shows that the transition is initiated by a cooling pulse followed by a decrease in precipitation. Through comparison with other archives, including North-Atlantic sedimentary records, it is proposed that the transition at 117.7 ka constitutes an internal climate response caused by a substantial input of freshwater from degraded ice-sheets by the end of the Eemian (∼120-118 ka).
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paleoclimate in continental northwestern europe during the eemian and earlyweichselian 125 97 ka insights from a belgian Speleothem
Climate of The Past, 2016Co-Authors: Stef Vansteenberge, Hai Cheng, Lawrence R. Edwards, Sophie Verheyden, Eddy Keppens, Philippe ClaeysAbstract:Abstract. The last interglacial serves as an excellent time interval for studying climate dynamics during past warm periods. Speleothems have been successfully used for reconstructing the paleoclimate of last interglacial continental Europe. However, all previously investigated Speleothems are restricted to southern Europe or the Alps, leaving large parts of northwestern Europe undocumented. To better understand regional climate changes over the past, a larger spatial coverage of European last interglacial continental records is essential, and Speleothems, because of their ability to obtain excellent chronologies, can provide a major contribution. Here, we present new, high-resolution data from a stalagmite (Han-9) obtained from the Han-sur-Lesse Cave in Belgium. Han-9 formed between 125.3 and ∼ 97 ka, with interruptions of growth occurring at 117.3–112.9 and 106.6–103.6 ka. The Speleothem was investigated for its growth, morphology and stable isotope (δ13C and δ18O) composition. The Speleothem started growing relatively late within the last interglacial, at 125.3 ka, as other European continental archives suggest that Eemian optimum conditions were already present during that time. It appears that the initiation of Han-9 growth is caused by an increase in moisture availability, linked to wetter conditions around 125.3 ka. The δ13C and δ18O proxies indicate a period of relatively stable conditions after 125.3 ka; however, at 120 ka the Speleothem δ18O registered the first signs of regionally changing climate conditions, being a modification of ocean source δ18O linked to an increase in ice volume towards the Marine Isotope Stage (MIS) 5e–5d transition. At 117.5 ka, drastic vegetation changes are recorded by Han-9 δ13C immediately followed by a cessation of Speleothem growth at 117.3 ka, suggesting a transition to significantly dryer conditions. The Han-9 record covering the early Weichselian displays larger amplitudes in both isotope proxies and changes in stalagmite morphology, evidencing increased variability compared to the Eemian. Stadials that appear to be analogous to those in Greenland are recognized in Han-9, and the chronology is consistent with other European (Speleothem) records. Greenland Stadial 25 is reflected as a cold/dry period within Han-9 stable isotope proxies, and the second interruption in Speleothem growth occurs simultaneously with Greenland Stadial 24.
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lead concentrations and isotope ratios in Speleothems as proxies for atmospheric metal pollution since the industrial revolution
Chemical Geology, 2015Co-Authors: Mohammed Allan, Hai Cheng, Lawrence R. Edwards, James U L Baldini, Nathalie Fagel, Maite Van Rampelbergh, Jean Riotte, David P Gillikin, Yves Quinif, Sophie VerheydenAbstract:Abstract Lead concentrations and isotope ratios from two Speleothems from the Han-sur-Lesse cave in southern Belgium were measured in order to study the ability of Speleothems to act as archives of atmospheric pollution. To address this aim we analyzed trace elemental Al and Pb compositions by LA-ICP-MS and ICP-MS as well as Pb isotopes by MC-ICP-MS. The results help to identify three intervals characterized by particularly high enrichment of Pb: from 1880 to 1905 AD, from 1945 to 1965 AD, and from 1975 to 1990 AD. The Speleothem record shows similar changes as the known historical atmospheric pollution level in Belgium. Lead isotope ratios discriminate between Pb sources and confirm that coal and gasoline combustion, combined with regional metallurgical activities, were the predominant Pb pollution sources in the stalagmites during the last 250 years. This study opens possibilities to determine anthropogenic versus natural metal sources in well-dated Speleothem archives.
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Trace elements in Speleothems. A short review of the state of the art
International Journal of Speleology, 2004Co-Authors: Sophie VerheydenAbstract:A state of the art of the research on trace elements of Speleothems is given. First studies focussed on problems such as the colour of Speleothems and the aragonite problem. Insitu studies and studies oriented towards a better understanding of vadose hydrology brought new insights in the controls on trace elemental composition of Speleothems. Recent studies deal with microscale analyses and annual and intra-annual chemistry changes. Further in-situ studies should be performed to further differentiate influences, such as climate, soil/weathering and local hydrology in order to better constrain possible transfer functions between the surface and a Speleothem.
Russell N. Drysdale - One of the best experts on this subject based on the ideXlab platform.
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partitioning of mg sr ba and u into a subaqueous calcite Speleothem
Geochimica et Cosmochimica Acta, 2019Co-Authors: Russell N. Drysdale, Giovanni Zanchetta, Isabelle Couchoud, Ilaria Isola, Illaria Baneschi, Massimo Guidi, Leonardo Piccini, Alan GreigAbstract:Abstract The trace-element geochemistry of Speleothems is becoming increasingly used for reconstructing palaeoclimate, with a particular emphasis on elements whose concentrations vary according to hydrological conditions at the cave site (e.g. Mg, Sr, Ba and U). An important step in interpreting trace-element abundances is understanding the underlying processes of their incorporation. This includes quantifying the fractionation between the solution and Speleothem carbonate via partition coefficients (where the partitioning (D) of element X (DX) is the molar ratio [X/Ca] in the calcite divided by the molar ratio [X/Ca] in the parent water) and evaluating the degree of spatial variability across time-constant Speleothem layers. Previous studies of how these elements are incorporated into Speleothems have focused primarily on stalagmites and their source waters in natural cave settings, or have used synthetic solutions under cave-analogue laboratory conditions to produce similar dripstones. However, dripstones are not the only Speleothem types capable of yielding useful palaeoclimate information. In this study, we investigate the incorporation of Mg, Sr, Ba and U into a subaqueous calcite Speleothem (CD3) growing in a natural cave pool in Italy. Pool-water measurements extending back 15 years reveal a remarkably stable geochemical environment owing to the deep cave setting, enabling the calculation of precise solution [X/Ca]. We determine the trace element variability of ‘modern’ subaqueous calcite from a drill core taken through CD3 to derive DMg, DSr, DBa and DU then compare these with published cave, cave-analogue and seawater-analogue studies. The DMg for CD3 is anomalously high (0.042 ± 0.002) compared to previous estimates at similar temperatures (∼8 °C). The DSr (0.100 ± 0.007) is similar to previously reported values, but data from this study as well as those from Tremaine and Froelich (2013) and Day and Henderson (2013) suggest that [Na/Sr] might play an important role in Sr incorporation through the potential for Na to outcompete Sr for calcite non-lattice sites. DBa in CD3 (0.086 ± 0.008) is similar to values derived by Day and Henderson (2013) under cave-analogue conditions, whilst DU (0.013 ± 0.002) is almost an order of magnitude lower, possibly due to the unusually slow Speleothem growth rates (
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Partitioning of Mg, Sr, Ba and U into a subaqueous Speleothem.
Geochimica et Cosmochimica Acta, 2019Co-Authors: Russell N. Drysdale, Giovanni Zanchetta, Isabelle Couchoud, Ilaria Isola, Illaria Baneschi, Massimo Guidi, Leonardo Piccinini, Alan Greig, Henry Wong, Jon WoodheadAbstract:The trace-element geochemistry of Speleothems is becoming increasingly used for reconstructing palaeoclimate, with a particular emphasis on elements whose concentrations vary according to hydrological conditions at the cave site (e.g. Mg, Sr, Ba and U). An important step in interpreting trace-element abundances is understanding the underlying processes of their incorporation. This includes quantifying the fractionation between the solution and Speleothem carbonate via partition coefficients (where the partitioning (D) of element X (DX) is the molar ratio [X/Ca] in the calcite divided by the molar ratio [X/Ca] in the parent water) and evaluating the degree of spatial variability across time-constant Speleothem layers. Previous studies of how these elements are incorporated into Speleothems have focused primarily on stalagmites and their source waters in natural cave settings, or have used synthetic solutions under cave-analogue laboratory conditions to produce similar dripstones. However, dripstones are not the only Speleothem types capable of yielding useful palaeoclimate information. In this study, we investigate the incorporation of Mg, Sr, Ba and U into a subaqueous calcite Speleothem (CD3) growing in a natural cave pool in Italy. Pool-water measurements extending back 15 years reveal a remarkably stable geochemical environment owing to the deep cave setting, enabling the calculation of precise solution [X/Ca]. We determine the trace element variability of ‘modern’ subaqueous calcite from a drill core taken through CD3 to derive DMg, DSr, DBa and DU then compare these with published cave, cave-analogue and seawater-analogue studies. The DMg for CD3 is anomalously high (0.042 ± 0.002) compared to previous estimates at similar temperatures (~8 °C). The DSr (0.100 ± 0.007) is similar to previously reported values, but data from this study as well as those from Tremaine and Froelich (2013) and Day and Henderson (2013) suggest that [Na/Sr] might play an important role in Sr incorporation through the potential for Na to outcompete Sr for calcite non-lattice sites. DBa in CD3 (0.086 ± 0.008) is similar to values derived by Day and Henderson (2013) under cave-analogue conditions, whilst DU (0.013 ± 0.002) is almost an order of magnitude lower, possibly due to the unusually slow Speleothem growth rates (
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A record of glacial-interglacial cycles over the last one million years from Antro del Corchia Speleothems
2012Co-Authors: Russell N. Drysdale, John Hellstrom, Isabelle Couchoud, Gianni Zanchetta, Jon Woodhead, Petra Bajo, Eleonora Regattieri, Ilaria IsolaAbstract:Antro del Corchia (Corchia Cave) is a large cave located in the Alpi Apuane karst of northern Tuscany, Italy. The cave receives most of its recharge from frontal systems crossing southwestern Europe and western Mediterranean, making the site sensitive to changes in ocean and atmospheric conditions in the North Atlantic. Parts of the cave are rich in Speleothems. A suite of stalagmites, flowstones and subaqueous mounds has been sampled to investigate regional palaeoclimate. Stable oxygen and carbon isotopes time series produced from these Speleothems, anchored in time using U-Th, U-U and U-Pb isotopic dating, preserve evidence for regional rainfall and temperature changes over millennial and glacial-interglacial timescales that can be linked via the marine-core record to North Atlantic palaeoclimate. A single Speleothem core, recovered from a subaqueous mound in the cave, preserves the last 11 glacial-interglacial cycles, constituting a rare and seemingly continuous palaeoclimate record spanning the last 960 ka. More detailed palaeoclimate reconstructions are emerging from the faster growing stalagmites from the cave. The entire Speleothem stack provides a means for establishing the timing of glacial terminations and inceptions.
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Using the 14C Bomb Pulse to Date Young Speleothems
Radiocarbon, 2011Co-Authors: Ed Hodge, Janece Mcdonald, Matthew Fischer, Dale Redwood, Quan Hua, Vladimir Levchenko, Russell N. Drysdale, Chris Waring, David FinkAbstract:Three modern Speleothems were sampled at high resolution for radiocarbon analysis to identify their bomb-pulse signatures and to construct chronologies. Each Speleothem exhibited a different 14C response, presumed to be related to site characteristics such as vegetation, temperature, rainfall, depth below the surface, and water pathway through the aquifer. Peak 14C activity for WM4 is 134.1 pMC, the highest cited thus far in the literature and suggestive of a lower inertia at this site. Dead carbon fractions for each stalagmite were calculated and found to be relatively similar for the 3 Speleothems and lower than those derived from Northern Hemisphere Speleothems. An inverse modeling technique based on the work of Genty and Massault (1999) was used to estimate soil carbon residence times. For each Speleothem, mean soil 14C reservoir ages differed greatly between the 3 sites, ranging from 2-6.5 to 32-46 yr.
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U–Pb geochronology of Speleothems by MC-ICPMS
Quaternary Geochronology, 2006Co-Authors: Jon D. Woodhead, Russell N. Drysdale, John Hellstrom, Roland Maas, Giovanni Zanchetta, Paul D. Devine, Eve TaylorAbstract:Abstract Building upon the work of Richards et al. [1998. U–Pb dating of a Speleothem of Quaternary age. Geochimica et Cosmochimica Acta 62, 3683–3688], we have developed a method for precise dating of Speleothems beyond the range of the U–Th technique using the U–Pb decay scheme. By coupling low-blank sample preparation procedures and multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) analytical methodologies developed for low-level Pb-isotope analysis, we find that, under ideal circumstances (radiogenic Speleothems with very low common Pb), U–Pb dating of Speleothems is not only possible, but also produces excellent age resolution—often comparable to or better than U–Th studies. Corrections for initial isotopic disequilibrium are necessary and exert a strong control on the achievable age uncertainty. The technique will be of immediate benefit in extending Speleothem-based climate proxy records beyond ∼500 ka and will also find other uses, such as the dating of associated sub-fossil remains, and providing constraints on rates of landscape evolution and neo-tectonic processes. Here we present initial results for Speleothems from the Nullarbor Plain, Western Australia, and the Alpi Apuane, Italy. The Nullarbor samples provide important new constraints on the development of aridity in Australia during the late Tertiary/early Quaternary, while the Apuane samples offer insights into the landscape history and uplift of that region.
Philippe Claeys - One of the best experts on this subject based on the ideXlab platform.
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paleoclimate in continental northwestern europe during the eemian and earlyweichselian 125 97 ka insights from a belgian Speleothem
Climate of The Past, 2016Co-Authors: Stef Vansteenberge, Hai Cheng, Lawrence R. Edwards, Sophie Verheyden, Eddy Keppens, Philippe ClaeysAbstract:Abstract. The last interglacial serves as an excellent time interval for studying climate dynamics during past warm periods. Speleothems have been successfully used for reconstructing the paleoclimate of last interglacial continental Europe. However, all previously investigated Speleothems are restricted to southern Europe or the Alps, leaving large parts of northwestern Europe undocumented. To better understand regional climate changes over the past, a larger spatial coverage of European last interglacial continental records is essential, and Speleothems, because of their ability to obtain excellent chronologies, can provide a major contribution. Here, we present new, high-resolution data from a stalagmite (Han-9) obtained from the Han-sur-Lesse Cave in Belgium. Han-9 formed between 125.3 and ∼ 97 ka, with interruptions of growth occurring at 117.3–112.9 and 106.6–103.6 ka. The Speleothem was investigated for its growth, morphology and stable isotope (δ13C and δ18O) composition. The Speleothem started growing relatively late within the last interglacial, at 125.3 ka, as other European continental archives suggest that Eemian optimum conditions were already present during that time. It appears that the initiation of Han-9 growth is caused by an increase in moisture availability, linked to wetter conditions around 125.3 ka. The δ13C and δ18O proxies indicate a period of relatively stable conditions after 125.3 ka; however, at 120 ka the Speleothem δ18O registered the first signs of regionally changing climate conditions, being a modification of ocean source δ18O linked to an increase in ice volume towards the Marine Isotope Stage (MIS) 5e–5d transition. At 117.5 ka, drastic vegetation changes are recorded by Han-9 δ13C immediately followed by a cessation of Speleothem growth at 117.3 ka, suggesting a transition to significantly dryer conditions. The Han-9 record covering the early Weichselian displays larger amplitudes in both isotope proxies and changes in stalagmite morphology, evidencing increased variability compared to the Eemian. Stadials that appear to be analogous to those in Greenland are recognized in Han-9, and the chronology is consistent with other European (Speleothem) records. Greenland Stadial 25 is reflected as a cold/dry period within Han-9 stable isotope proxies, and the second interruption in Speleothem growth occurs simultaneously with Greenland Stadial 24.
