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See detailCharacterizing the Eemian-Weichselian transition in northwestern Europe with three multiproxy speleothem archives from the Belgian Han-sur-Lesse and Remouchamps cave systems
Vansteenberge, Stef; Verheyden, Sophie; Genty, Dominique et al

in Quaternary Science Reviews (2019)

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 ... [more ▼]

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 these transitions remain still poorly understood. Here, three speleothem archives from two different cave systems in Belgium (Han-sur-Lesse and Remouchamps) are investigated using a multiproxy approach in order to characterize the last interglacial to glacial transition. The studied samples roughly span the period between 125 ka and 100 ka, covering a large part of the Eemian and early Weichselian. The speleothems show a high reproducibility for δ13C, which is interpreted as a proxy for past vegetation activity, controlled by vegetation assembly above the cave. All three speleothems show a drastic increase in δ13C between 118 to 117 ka, reflecting a rapid change of vegetation assembly from last interglacial temperate tree species towards glacial more open grass vegetation. This event shows a strong affinity in terms of timing and climatic expression with the Late Eemian Aridity Pulse (LEAP) at 118 ± 1 ka, identified in pollen records from Western Germany. Aligning the chronologies of the two independently dated Han-sur-Lesse speleothem records enables a more precise absolute chronology and provides an age of 117.7 ± 0.5 ka to the start of this event in the Belgian speleothems. This event marks a distinct transition in the Belgian speleothem proxies between Eemian optimum conditions and increased variability during the glacial inception and the start of this event at 117.7 ± 0.5 ka is therefore proposed as the Eemian- Weichselian transition and consequently the start of the glacial inception in the studied speleothems. High-resolution analysis shows that the 117.7 ± 0.5 ka event is initiated by a cooling pulse followed by a decrease in precipitation. A similar short-lived cooling event is also registered in multiple North-Atlantic sediment archives. This study hypothesizes that the origin of the cooling event at 117.7 ka is an internal climate response caused by the substantial amount of freshwater input from degraded ice-sheets by the end of the Eemian (~120-118 ka). There is thus a clear climatic connection between the Belgian speleothems and other continental European archives and North Atlantic marine archives, providing the possibility of improving less constrained chronologies by alignment to the independently constructed speleothem age-depth model presented in this study. [less ▲]

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See detailHigh-resolution reconstruction of 8.2 ka BP event documented in Père Noël cave, southern Belgium
Allan, Mohammed ULiege; Fagel, Nathalie ULiege; van der Lubbe, H.J.L. et al

in Journal of Quaternary Science (2018)

A distinct shift in 18O,13C and trace element contents of the Père Noël (PN) stalagmite from southern Belgium revealed an abrupt climatic anomaly at 8.13±0.03 ka BP (Before Present=before 1950 AD ... [more ▼]

A distinct shift in 18O,13C and trace element contents of the Père Noël (PN) stalagmite from southern Belgium revealed an abrupt climatic anomaly at 8.13±0.03 ka BP (Before Present=before 1950 AD). This anomaly is characterized by a maximum drop in the 18O (-1.4‰ compared the mean) between 8.13 and 8.10 ka BP (±0.03). This drop of 18O coincides with a decrease in 13C and trace element (Sr, Ba and Mg) concentrations suggesting drier conditions. Our precise chronology provides the timing of the outburst of proglacial lakes Agassiz and Ojibway that caused the 18O, 13C and trace elemental anomalies at 8.13 – 8.10 ±0.03 ka BP, which corresponds to the 8.2 ka BP event. The PN stalagmite bears δ18O values in fluid inclusions that covariate with the δ18O values in calcite, suggesting that the speleothem calcite δ18O primarily reflects variations in the rainfall δ18O. Comparison of PN record with different marine and terrestrial archives during the 8.2 ka BP event shows a good agreement in timing and duration suggesting that the PN speleothem can be regarded as a valuable proxy to better understand the 8.2 ka BP event. [less ▲]

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See detailReconstruction of atmospheric lead pollution during the Roman period recorded in Belgian ombrotrophic peatlands cores
Allan, Mohammed ULiege; Pinti, Daniele; Ghaleb, bassam et al

in Atmosphere (2018)

Two peat cores from two bogs were used to record changes in the atmospheric Pb accumulation rate (Pb AR) in Belgium during the Roman period. The two records were compared to assess the reliability of peat ... [more ▼]

Two peat cores from two bogs were used to record changes in the atmospheric Pb accumulation rate (Pb AR) in Belgium during the Roman period. The two records were compared to assess the reliability of peat cores as archives of atmospheric Pb deposition and to establish histories of atmospheric emissions from anthropogenic sources. To address these issues we analyzed Pb concentration and its isotopes, using ICP-MS, LA-ICP-MS and MC-ICP-MS in two peat sections, spanning 1000 yr each. Lead concentrations in the two cores range from 0.1 to 60 μg g−1, with the maxima between 15 and 60 μg g−1. The average natural background of Pb AR varies between 0.003 and 0.07 mg m-2 yr-1 and the maximum ranges from 0.7 to 1.2 mg m-2 yr-1 between 50 BC and AD 215. The highest Pb AR exceed the pre-Roman period values by a factor of 17-80. Pb isotopic composition indicates that mining and metallurgical activities were the predominant sources of pollution during the Roman period. The Pb AR and chronologies in the Belgian peat cores are consistent with those reported for other continental archives as lake sediments, peat and ice cores. [less ▲]

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See detailEvidence for solar influence in a Holocene speleothem record (Père Noël cave, SE Belgium)
Allan, Mohammed ULiege; Deliège, Adrien ULiege; Verheyden, sophie et al

in Quaternary Science Reviews (2018)

We present a decadal-centennial scale Holocene climate record based on trace elements contents from a 65cm stalagmite from Belgian Père Noël cave. “Père Noël” (PN) stalagmite covers the last 12.7 ka ... [more ▼]

We present a decadal-centennial scale Holocene climate record based on trace elements contents from a 65cm stalagmite from Belgian Père Noël cave. “Père Noël” (PN) stalagmite covers the last 12.7 ka according to U/ Th dating. High spatial resolution measurements of trace elements (Sr, Ba and Mg) were done by Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Trace elements profiles were interpreted as environmental and climate changes in the Han-sur-Lesse region. Power spectrum estimators and continuous wavelet transform were applied on trace elements time series to detect any statistically significant periodicities in the PN stalagmite. Spectral analyses reveal decadal to millennial periodicities (i.e., 68–75, 133–136, 198–209, 291–358, 404–602, 912–1029 and 2365–2670 yr) in the speleothem record. Results were compared to reconstructed sunspot number data to determine whether solar signal is presents in PN speleothem. The occurrence of significant solar periodicities (i.e., cycles of Gleissberg, de Vries, unnamed 500 years, Eddy and Hallstatt) supports for an impact of solar forcing on PN speleothem trace element contents. Moreover, several intervals of significant rapid winter change were detected during the Holocene at 10.3, 9.3–9.5, around 8.2, 6.4–6.2, 4.7–4.5, and around 2.7 ka BP. Those intervals are similar to the cold winter events evidenced in different natural paleoclimate archives, suggesting common climate forcing mechanisms related to changes in solar irradiance. [less ▲]

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See detailDating young stalagmite using 210Pb excess method: example from Han-sur-Lesse cave, Belgium
Ghaleb, Bassam ULiege; Allan, Mohammed ULiege; verheyden, sophie et al

Conference (2018, April 12)

Speleothem cave deposits (particularly stalagmites) represent often high–resolution continental records for reconstruction of paleoclimate and/or paleoenvironmental conditions through their trace elements ... [more ▼]

Speleothem cave deposits (particularly stalagmites) represent often high–resolution continental records for reconstruction of paleoclimate and/or paleoenvironmental conditions through their trace elements concentrations (e.g., Mg, Sr and Ba) and stable isotopes compositions 18O and 13C (Fairchild, et al., 2000, 2001; McDermott, 2004). The advantage of using very young speleothems (1-120 yrs timescale) is the possibility to validate such reconstructions when compared with historical and instrumental records (e.g., meteorological parameters). U-series radiochronology remains the most suitable method to obtain reliable absolute ages of speleothems even for relatively young deposits, avoiding uncertainties related to multiple sources of CO2. In cases of pristine and clean speleothems with relatively high U-contents, precise U/Th ages can be obtained even for very recent stalagmite (e.g., Shen et al, 2013). However, this is rarely the case because speleothems often contain low U-contents (ppb levels) and traces of detrital contaminants, which require often complicated age corrections. Such corrections result in relatively high uncertainties on the final age calculation. We present here the results of 210Pb measurements carried out on high growth rate and laminated stalagmite from Han-sur Lesse cave, southern Belgium. The 210Pb results show a clear well defined exponential with depth decreasing allowing to calculate an age-depth model. These 210Pb ages were confronted to ages of the stalagmite obtained by counting laminae and considered as true ages. The results show a good agreement between the two ages within the analytical errors and open a new potential for dating recent not laminated speleothems using 210Pb excess method. [less ▲]

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See detailHolocene paleoclimate reconstructions from Belgian continental archives (HOPES)
Allan, Mohammed ULiege; lenoir, guillaume; Verheyden, sophie et al

Conference (2018, April)

Comparing climate reconstructions based on proxy data approach with climate modelling enables to test both assumptions underlying the interpretation of climate reconstructions and to refine predictive ... [more ▼]

Comparing climate reconstructions based on proxy data approach with climate modelling enables to test both assumptions underlying the interpretation of climate reconstructions and to refine predictive models. Among geological archives, speleothems (secondary carbonate deposits in caves) and peatbogs are now regarded as important archives of past climatic and environmental conditions on the continents, offering a number of advantages relative to other continental archives (such as lake sediments, tree rings, ice cores). Both archives, presented in Belgium, are reliable continental environmental archives of high interest due to their dating possibilities and their possibility to preserve multi-proxy records of environmental and climatic dynamics. Combining studies on speleothems and peatbogs from the same area was provided an age-constrained reconstruction of climatic variability at decennial resolution for key intervals of the Holocene (6.5 to 5.5 ka, 5.2 to 4.2 ka and 3.2 to 2.2 ka). The reconstructed precipitation and temperature curves in NW European settings, as proposed in HOPES, are essential to better constrain the Northern Hemisphere climatic record and to test climate models. Our strategy was derived from a comparative study of two continental archives: speleothems and peatbogs. Time series of elemental and stable isotope geochemistry were established for the 2 archives. Precipitation and humidity conditions over Belgium was reconstructed by integration of results derived from the two continental archives. Such comparison allows to reduce the bias related to the specific sensitivity to climate changes of each archive. Time-series was first screened using classical time-series analysis techniques in order to detect potential quasi-periodic patterns in the paleoclimate records. As a second step, statistical modeling will be developed to associate peatbog and speleothem data in a single, consistent framework at the Belgian scale, and then to associate these data into larger data network. Our data will thus complement the information on rapid climate change and regional variability across Europe gained through research programs funded by the European Science Fundation and the European commission like Holivar (www.esf.org), ACCROTELM (www2.glos.ac.uk/accrotelm/) or Past4Future (www.past4future.eu). [less ▲]

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See detailEarthquakes as collapse precursors at the Han-sur-Lesse Cave in the Belgium Ardennes
Camelbeeck, Thierry; Quinif, Yves; Verheyden, Sophie et al

in Geomorphology (2018), 308

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See detailConstruction of high-resolution trace element time-series in Belgian speleothems by LA-ICP-MS
Allan, Mohammed ULiege; verheyden, sophie; crucifix, michel et al

Conference (2017, August 17)

Speleothems, presented in Belgium, are now regarded as valuable archive of paelenvirenmental variations on the continents, offering a number of advantages relative to other continental climate proxy ... [more ▼]

Speleothems, presented in Belgium, are now regarded as valuable archive of paelenvirenmental variations on the continents, offering a number of advantages relative to other continental climate proxy recorders such as lake sediments. They are reliable continental archives of high interest due to their dating possibilities and their possibility to preserve multi-proxy records of environmental and climatic dynamics. Establishing high-resolution trace element time series in speleothems requires analytical techniques capable of representative sampling at sub-annual spatial resolution (on order of 22 µm in this study). In the Belgian Pere Noel cave (PN), high spatial resolution measurements of trace elements (e.g., Mg, Sr, Ba) were realized by using LA-ICP-MS and compared with results from lower resolution techniques (ICP-MS). The results from both techniques have been analysed in order to assess the capability of each technique to reconstruct climate changes at high resolution from PN stalagmite. Results showed that LA-ICP-MS technique allows a rapid analysis of multiple elemental concentrations, and uses minimal sample volume allowing for replicate sampling and availability of almost the entire original sample for other analyses. [less ▲]

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See detailDoes Belgian Holocene speleothem record solar forcing and cold events?
Allan, Mohammed ULiege; Deliège, Adrien ULiege; Nicolay, Samuel ULiege et al

in Climate of the Past Discussions (2017)

We present a decadal-centennial scale Holocene climate record based on trace elements contents from a 65 cm stalagmite (Père Noël) from Belgian Père Noël cave. Père Noël (PN) stalagmite covers the last 12 ... [more ▼]

We present a decadal-centennial scale Holocene climate record based on trace elements contents from a 65 cm stalagmite (Père Noël) from Belgian Père Noël cave. Père Noël (PN) stalagmite covers the last 12.7 ka according to U/Th dating. High spatial resolution measurements of trace elements (Sr, Ba, Mg and Al) were done by Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Trace elements profiles were interpreted as environmental and climate changes in the Han-sur-Lesse region. Power spectrum estimators and continuous wavelet transform were applied on trace elements time series to detect any statistically significant periodicities in the PN stalagmite. Spectral analyses reveal decadal to millennial periodicities (i.e., 68–75, 133–136, 198–209, 291–358, 404–602, 912–1029 and 2365–2670 yr) in the speleothem record. Results were compared to reconstructed sunspot number data to determine whether solar signal is presents in PN speleothem. The occurrence of significant solar periodicities (i.e., cycles of Gleissberg, de Vries, unnamed 500 years, Eddy and Hallstat) supports for an impact of solar forcing on PN speleothem trace elements contents. Moreover, several intervals of significant rapid climate change were detected during the Holocene at 10.3, 9.3–9.5, around 8.2, 6.4–6.2, 4.7–4.5, and around 2.7 ka BP. Those intervals are similar to the cold events evidenced in different natural paleoclimate archivers, suggesting common climate forcing mechanisms related to changes in solar irradiance. [less ▲]

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See detailBelgian speleothem records Holocene cold events?
Allan, Mohammed ULiege; Deliège, Adrien ULiege; Nicolay, Samuel ULiege et al

Poster (2017, May 12)

Speleothem is now regarded as valuable archive of climatic conditions on the continents, offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and ... [more ▼]

Speleothem is now regarded as valuable archive of climatic conditions on the continents, offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores. High spatial resolution measurements of Mg, Al, Sr, Ba were realized by using laser-ablation inductively coupled plasma mass spectrometry in the Belgian Pere Noel cave. A stalagmite from the Pere Noel (PN) cave representing 12000 years dated by U/Th method. Trace element variations in speleothem are a reflection of hydrochemical conditions. These changes were interpreted as indications of changes in climate in the Han-sur-Lesse region. The similar patterns found in δ 18O, δ 13C and chemical composition along the Pere Noel stalagmite suggests that trace elements in speleothems have the potential to provide high resolution insights into palaeoclimatic variability during the Holocene. A deeper analysis reveals several periods of significant rapid climate change during the Holocene (at 10.7-9.2 ka, 8.2-7.9 ka, 7.2-6.2 ka, 4.8-4.5 ka, and 3-2.4 ka BP), which are similar to the cold events detected from different natural paleoclimate archivers. A comparison between the geochemical analysis of Père Noël speleothem and solar activity (sunspot number) reveals a significant correlation. Spectral analysis methods reveal common solar periodicities (Gleissberg cycle, de Vries cycle, unnamed 500 year, Eddy cycles, and Hallstatt cycle). The geochemical analyses have the potential to prove that PN speleothem is sensitive to changes in solar activity on centennial and millennial timescales during the Holocene. [less ▲]

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See detailLa pollution atmosphérique enregistrée dans les stalagmites de Han-sur-Lesse
Allan, Mohammed ULiege; Fagel, Nathalie ULiege; Verheyden, sophie

Conference (2016, November 12)

Les spéléothèmes sont maintenant considérées comme précieuses archives climatiques et environnementales sur les continents, offrant un certain nombre d'avantages par rapport à d'autres archives ... [more ▼]

Les spéléothèmes sont maintenant considérées comme précieuses archives climatiques et environnementales sur les continents, offrant un certain nombre d'avantages par rapport à d'autres archives continentales (les sédiments lacustres, les carottes de glace….). Cette archive peut être aisément datables (U/Th, comptage de lamines et 14C), et présentent une haute résolution temporelle (décennale à saisonnière). Cependant, leur potentiel pour l'enregistrement de la pollution de l'environnement est largement inexploré et principalement axé sur la quantification des contributions d'aérosols dans des grottes touristiques. Cette étude est un des premières études qui utilise les spéléothèmes pour retracer la pollution atmosphérique. Basé sur deux spéléothèmes collectées dans la grotte de Han-sur-Lesse (S-Belgique), ce travail a deux objectifs : 1) le premier est de quantifier la concentration du Pb pour la dernière 250 ans, 2) le second objectif est de définir les sources anthropiques prédominantes de Pb en utilisant les rapports isotopiques du Pb et en basant sur les comparaisons avec les données historiques des activités anthropogéniques en Europe et la Belgique. Les concentrations en éléments traces (Al et Pb) (mesurées par LA-ICP-MS et ICP-MS) et les rapports isotopiques du Pb (mesurées par MC-ICP-MS) permettent d'identifier trois intervalles caractérisés par un enrichissement particulier en Pb : de 1880 à 1905 AD, de 1945 à 1965 AD, et de 1975 à 1990 AD. Les spéléothèmes montrent des changements similaires au niveau historique de la pollution atmosphérique connu en Belgique. Les rapports isotopiques du Pb distinguent clairement les sources de Pb et confirment que le charbon et la combustion de l'essence combinée avec des activités métallurgiques régionales étaient les sources prédominantes de la pollution au cours des 250 dernières années. Cette étude met l'accent sur la capacité des spéléothèmes d’enregistrer la pollution atmosphérique. [less ▲]

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See detailHolocene paleoclimate reconstructions from belgian continental archives
Allan, Mohammed ULiege; VERHEYDEN, sophie; CRUCIFIX, Michel et al

Poster (2016, June 28)

Speleothems and peatbogs presented in Belgium are interesting archives for atmospheric pollution record and climate variability. Both archives are reliable continental environmental archives of high ... [more ▼]

Speleothems and peatbogs presented in Belgium are interesting archives for atmospheric pollution record and climate variability. Both archives are reliable continental environmental archives of high interest due to their dating possibilities and their possibility to preserve multi-proxy records of environmental and climatic dynamics. Combining studies on speleothems and peatbogs from the same area will provide an age-constrained reconstruction of climatic variability at annual resolution for key intervals of the Holocene. The reconstructed precipitation and temperature curves in NW European settings, as proposed in HOPES, are essential to better constrain the Northern Hemisphere climatic record and to test climate models. Our strategy is derived from a comparative study of two continental archives speleothems and peatbogs. Time series of elemental and stable isotope geochemistry will be established for the 2 archives. For peatbog, the reconstructions of temperature (derived from stable C and O isotope), precipitation (derived from humification) and dust flux (from elementary geochemical signature) would track climate changes with subdecadal resolution. As an innovative part, Laser Ablation analyse of elemental geochemistry on impregnated peat section will allow to reach an annual resolution in the dust flux. For speleothems, records of temperature (derived from oxygen and carbon isotopic composition of calcite) and effective rainfall (derived from geochemical ratios) would reach a seasonal resolution. [less ▲]

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See detailHolocene paleoenvironmental reconstructions from Belgian peatbog
Allan, Mohammed ULiege; VERHEYDEN, sophie; Le roux, gael et al

Conference (2016, January 27)

Atmospheric deposition is an important part of the global climate system, and plays a key role in the marine and terrestrial biogeochemical cycles as a source for major and trace nutrient elements ... [more ▼]

Atmospheric deposition is an important part of the global climate system, and plays a key role in the marine and terrestrial biogeochemical cycles as a source for major and trace nutrient elements. Reconstruction of atmospheric deposition is crucial to understand the effects of the increased atmospheric depositions induced by humans on the environment and to help understanding Holocene climate variability. This study investigated potential paleoenvironmental proxies provided by major and trace elements and stable isotopes compositions of peat bogs. Peat bog cores were collected from Hautes-Fagnes plateau (Misten bog) (SE-Belgium). The analyses of Rare Earth Elements (REE) and lithogenic element concentrations as well as Nd isotopes were performed by HR-ICP-MS and MC-ICP-MS respectively, in a  7 m peat section representing 7300 years, dated by 210Pb and 14C methods. The Misten bog is highly affected by atmospheric supplies (natural and anthropogenic) and can be used to establish the changes in atmospheric dust during the Mid-Late Holocene. Dust fluxes show pronounced increase at 3200-2800BC, 600BC, AD600, 1000AD, 1200AD and from 1700 AD corresponding to local and regional human activities combined with climate change. Peat humification and testate amoebae were used to evaluate hydroclimatic conditions. The Nd values show large variability, between -5 and –13, identifying three major sources of dust: local soils, distal volcanic and desert particles. Our results provide evidence that climate forcing may be detected in ombrotrophic peat, even for the historical period that is characterised by a mixed climate-human control. [less ▲]

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See detailAtmospheric metal pollution over the last 250 years inferred from speleothem geochemistry
Allan, Mohammed ULiege; Fagel, Nathalie ULiege; Verheyden, Sophie

Conference (2015, August 17)

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 ... [more ▼]

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 Pb-enriched intervals: from 1880 to 1905 AD, from 1945 to 1965 AD, and from 1975 to 1990 AD. The speleothem record is consistent with the evolution of atmospheric pollution in Belgium. Lead isotope ratios 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 research underscores the importance of speleothems as a valuable tool for the discrimination between anthropogenic and natural lead contributions in the environment and consequently for quantifying the anthropogenic contribution or determining natural background values in continental settings. [less ▲]

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See detailHolocene palaoenvironmental records in PN speleothem (Han-sur-Lesse cave, southern Belgium
Allan, Mohammed ULiege; Fagel, Nathalie ULiege; Verheyden, Sophie

Conference (2015, April 16)

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See detailA 500-year seasonally resolved δ 18 O and δ 13 C, layer thickness and calcite aspect record from a speleothem deposited in the Han-sur-Lesse cave, Belgium
Van Rampelbergh, Maïte; Verheyden, Sophie; Allan, Mohammed ULiege et al

in Climate of the Past (2015), 11

Speleothem δ18O and δ13C signals enable climate reconstructions at high resolution. However, scarce decadal and seasonally resolved speleothem records are often diffi- cult to interpret in terms of climate ... [more ▼]

Speleothem δ18O and δ13C signals enable climate reconstructions at high resolution. However, scarce decadal and seasonally resolved speleothem records are often diffi- cult to interpret in terms of climate due to the multitude of factors that affect the proxy signals. In this paper, a fast- growing (up to 2 mm yr−1) seasonally laminated speleothem from the Han-sur-Lesse cave (Belgium) is analyzed for its δ18O and δ13C values, layer thickness and changes in cal- cite aspect. The studied record covers the period between AD 2001 and 1479 as indicated by layer counting and con- firmed by 20 U / Th ages. The Proserpine proxies are sea- sonally biased and document drier (and colder) winters on multidecadal scales. Higher δ13C signals reflect increased prior calcite precipitation (PCP) and lower soil activity dur- ing drier (and colder) winters. Thinner layers and darker calcite relate to slower growth and exist during drier (and colder) winter periods. Exceptionally dry (and cold) winter periods occur from 1565 to 1610, at 1730, from 1770 to 1800, from 1810 to 1860, and from 1880 to 1895 and correspond to exceptionally cold periods in historical and instrumental records as well as European winter temperature reconstruc- tions. More relative climate variations, during which the four measured proxies vary independently and display lower am- plitude variations, occur between 1479 and 1565, between 1610 and 1730, and between 1730 and 1770. The winters during the first and last periods are interpreted as relatively wetter (and warmer) and correspond to warmer periods in historical data and in winter temperature reconstructions in Europe. The winters in the period between 1610 and 1730 are interpreted as relatively drier (and cooler) and correspond to generally colder conditions in Europe. Interpretation of the seasonal variations in δ18O and δ13C signals differs from that on a decadal and multidecadal scale. Seasonal δ18O variations reflect cave air temperature variations and suggest a 2.5◦C seasonality in cave air temperature during the two relatively wetter (and warmer) winter periods (1479–1565 and 1730–1770), which corresponds to the cave air temper- ature seasonality observed today. Between 1610 and 1730, the δ18O values suggest a 1.5◦C seasonality in cave air tem- perature, indicating colder summer temperatures during this drier (and cooler) interval. The δ13C seasonality is driven by PCP and suggests generally lower PCP seasonal effects be- tween 1479 and 1810 compared to today. A short interval of increased PCP seasonality occurs between 1600 and 1660, and reflects increased PCP in summer due to decreased win- ter recharge. [less ▲]

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See detailLead concentrations and isotope ratios in speleothems as proxies for atmospheric metal pollution since the Industrial Revolution
Allan, Mohammed ULiege; Fagel, Nathalie ULiege; Van Rampelbergh, Maïte et al

in Chemical Geology (2015)

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 ... [more ▼]

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. [less ▲]

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See detailSeasonal variations recorded in cave monitoring results and a 10 year monthly resolved speleothem δ18O and δ13C record from the Han-sur-Lesse cave, Belgium
Van Rampelbergh, Maïte; Verheyden, Sophie; Allan, Mohammed ULiege et al

in Climate of the Past Discussions (2014), 10

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See detailLe plomb atmosphérique enregistré dans les stalagmites de Han-sur-Lesse
Allan, Mohammed ULiege; Verheyden, Sophie

Conference (2013, November 16)

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See detailHolocene dust record in a NW European peat bog: A multiproxy approach
Allan, Mohammed ULiege; Le Roux, Gael; Verheyden, Sophie et al

Conference (2013, August 28)

Dust deposition in southern Belgium is estimated from the geochemical signature of an ombrotrophic bog. The analyses of Rare Earth Elements (REE) and lithogenic element concentrations as well as Nd ... [more ▼]

Dust deposition in southern Belgium is estimated from the geochemical signature of an ombrotrophic bog. The analyses of Rare Earth Elements (REE) and lithogenic element concentrations as well as Nd isotopes were performed by HR-ICP-MS and MC-ICP-MS respectively, in a  6 m peat section representing 5300 years, from 30 BC to 5300 BC dated by the 14C method. REE concentration variations in peat samples were used as a dust proxy and the Nd isotopes to trace the sources. Peat humification and testate amoebae were used to evaluate hydroclimatic conditions. The range of dust deposition varied from 0.03 to 4 g m-2 yr-1. The highest dust fluxes were observed from 800 to 600 BC, and from 3200 to 2800 BC and correspond to cold periods. The Nd values show large variability, between -5 and –13, identifying three major sources of dust: local soils, distal volcanic and desert particles. By comparing our results with the dust recorded in other peat bogs and ice cores from different latitudes, we evidence that the Misten peat is a valid archive for dust deposition. [less ▲]

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