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See detailReconstructing Early Atlantic to Early Subatlantic peat-forming conditions of the ombrotrophic Misten Bog (eastern Belgium) on the basis of high-resolution analyses of pollen, testate amoebae and geochemistry
Streel, Maurice ULiege; Paillet, Marc ULiege; Beghin, Jérémie ULiege et al

in Geologica Belgica (2018), 21(3-4),

A seven metres thick peat bog (Misten, Hautes-Fagnes, Belgium) has been studied at high resolution in order to reconstruct the conditions of peat formation and evolution on the basis of pollen, testate ... [more ▼]

A seven metres thick peat bog (Misten, Hautes-Fagnes, Belgium) has been studied at high resolution in order to reconstruct the conditions of peat formation and evolution on the basis of pollen, testate amoebae analysis, and geochemistry. The sampled section of the peat bog corresponds to the most part of the Atlantic period, all the Subboreal period and the earliest Subatlantic period, i.e. a time interval between 7300 cal BP and 2000 cal BP. The identification of tie-points in the pollen assemblages recognized in a previous work (Persch, 1950) performed in the periphery of the same peat-bog, allows accurate correlation of the two sites, 460 cm thickness of peat in the central part corresponding to 230 cm thickness of peat in the periphery. The well constrained dates of the tie-points in the present work provide a more precise chronology of the events identified in Persch’s pollen diagram. A comparison of pollen data in both sites demonstrates that, as expected, the Corylus pollen rain is proportionally more important and the Quercetum mixtum pollen rain proportionally less important in the central area of the peat bog than in the periphery. The study of the testate amoebae in the central part of the peat bog is the major contribution of the present work. A stratigraphically constrained analysis resulted in the identification of five biozones, the zonation being mainly built on the fluctuations observed between Archerella (Amphitrema) flavum and Difflugia pulex. Three transfer functions have been applied and compared. Coupled with the humification values of each level, it allows a very accurate approach of the water-table level, and hence of local climatic conditions, at the time of the peat formation. Combination of pollen results and testate amoebae zonal subdivisions allows the definition, dating and interpretation of 18 rather short time intervals with an approximate duration of 200 to 300 years each. Our results validate and expand a previously published climate interpretation that combined geochemical data and a preliminary testate amoebae analysis. [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 detailHigh-resolution reconstruction of 8.2 ka event recorded in Belgian Holocene speleothems
Allan, Mohammed ULiege; verhyden, sophie; Fagel, Nathalie ULiege

Scientific conference (2017, August 24)

Two abrupt shifts in d18O and trace element contents of a stalagmite from the northwestern European continent (southern Belgium) suggest that two cold anomalies occurred beginning at 8.4±0.04 and ending ... [more ▼]

Two abrupt shifts in d18O and trace element contents of a stalagmite from the northwestern European continent (southern Belgium) suggest that two cold anomalies occurred beginning at 8.4±0.04 and ending at 8.15±0.03, possibly reflecting climatic effects associated with the 8.2 ka event. The younger of the two anomalies lasted about 30 years, from 8.18 to 8.15±0.03 ka, with a maximum d18O amplitude of 1.4‰. Trace element (Sr, Ba and Mg) peaks coincide with this second drop of d18O. The anomaly initiation is marked by Sr, Ba and Mg concentration peaks suggesting drier conditions during the coldest years, consistent with previous research in the North Atlantic. The earlier anomaly in trace element, d18O records is associated with generally cold but wet conditions at 8.4 ka, lasted 50 years, and ended abruptly. The interval from 8.4 ka to 8.15 ka was less favorable for speleothem deposition, with denser speleothem calcite deposition and lower growth rate, consistent with a cold, dry climate. The clear recovery in both temperature and rainfall between after both anomalies (8.2 and 8.4 ka), suggests that these anomalies are distinct, and may represent two episodes of AMOC weaking related to the drainage of proglacial lakes Agassiz and Ojibway. [less ▲]

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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 detailLacustrine clay mineral assemblages as a proxy for land-use and climate changes over the last 4 kyr: The Amik Lake
El Ouahabi, Meriam ULiege; Hubert, Aurelia ULiege; Allan, Mohammed ULiege et al

Poster (2017, May 10)

Lake sediments are sensitive to landscape changes and most of these changes seem to be modulated by land-use (anthropogenic factors) coupled to palaeoenvironmental/palaeoclimatic changes. In its detrital ... [more ▼]

Lake sediments are sensitive to landscape changes and most of these changes seem to be modulated by land-use (anthropogenic factors) coupled to palaeoenvironmental/palaeoclimatic changes. In its detrital fraction, the lacustrine sediments record the history of soil erosion within its catchment via the inputs of clays and others detrital products. Within a Mediterranean context, the study investigates the upper sediments infilling the central part of the Amik basin in southern Turkey. This tectonic basin was occupied and exploited by modern human at least since 6000-7000 BC. We focus on the clay mineralogy (x-ray diffraction on oriented aggregates) and magnetic susceptibility measurements (Bartington) of the sedimentary record in the area over the last 4000 years, to assess environmental changes in relation with the different land uses and/or weathering during the successive Bronze, Iron, Roman, Islamic/Ottoman and Modern civilizations. The clay fraction of Amik Lake sediments comprises smectite, kaolinite, illite, chlorite and chlorite/smectite mixed layers that are the inherited clay phases. A relative change in abundance and crystallinity and chemistry of illite attests that environmental conditions evolved in the Amik Plain from the Bronze to Modern Age in relation with climates and/or land-use changes. The history of the Amik Lake reveals different soil erosion episode. The most intense erosion phase occurred during the Bronze/Iron Ages as indicated by the clay and magnetic susceptibility proxies. The Roman period was an exceptional period with soil erosion products arriving from the watershed, probably due the water channelization. A reduction of soil erosion occurred during the post Roman period until nowadays. Significant pedogenesis transformations are evidenced, especially during the Islamic/Ottoman periods suggesting intense chemical weathering conditions related to climate change. [less ▲]

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See detailVARIATIONS OF TREE RING WIDTH AND CHEMICAL COMPOSITION OF WOOD OF PINE GROWING IN THE AREA NEARBY CHEMICAL FACTORIES
Sensula, Barbara; Wilczynski, Slawomir; Monin et al

in Geochronometria: Journal on Methods and Applications of Absolute Chronology (2017), 44

This study reports the variation of tree-ring widths and annual variation of concentration of metals (Na, Mg, Fe, Ni, Cu, Zn, Pb) in pine growing nearby chemical factories. The conifers (Pinus silvestris ... [more ▼]

This study reports the variation of tree-ring widths and annual variation of concentration of metals (Na, Mg, Fe, Ni, Cu, Zn, Pb) in pine growing nearby chemical factories. The conifers (Pinus silvestris L.) investigated in this study covered the time span from 1920s to 2010 AD. Tree-ring widths were measured, dated and rechecked using the COFECHA. Radial trace-element profiles were determined by Laser Ablation Inductively Coupled Plasma Mass Spectrometry. The combined usage of tree ring width and chemical composition of wood provides historic records of anthropogenic im- pact on the environment and allows identifying the behavior adaptation of trees to the pollution. Data of pine tree cores collected from the sites nearby chemical factories show increasing levels of pollu- tion linked to the increasing of industrial activities in Poland and subsequent dust fallout around the site. This study evidences that tree rings can be used as archives of past environmental contamination. [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 speleothem and peat bog archives
Allan, Mohammed ULiege; VERHEYDEN; CRUCIFIX, Michel et al

Poster (2016, January 28)

The geological materials (speleothems and peatbogs) presented in Belgium (Hautes-Fagnes Plateau, Ardennes caves) are interesting archives for atmospheric pollution record and climate variability. Both ... [more ▼]

The geological materials (speleothems and peatbogs) presented in Belgium (Hautes-Fagnes Plateau, Ardennes caves) are interesting archives for atmospheric pollution record and climate variability. Both archives are easily dated (U/Th and counting for laminated speleothems, 210Pb and 14C for peatbogs), have a high temporal resolution (decadal to seasonal), contain multiple measurable parameters (elemental geochemistry, stable isotopes, radiogenic Nd and Pb isotopes, pollens, rates of peat humification, luminescence and thickness of laminated speleothems) and depending on environmental conditions of temperature and / or humidity. The aim of this study is to determine the sensitivity of both archives (speleothems and peatbogs) to human perturbations and climate changes. Our ultimate goal is to contribute to a better understanding of natural interglacial climate variability by generating and confronting high resolution paleoclimate reconstructions from 2 continental archives. [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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