References of "Fagel, Nathalie"
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See detailA climate model from 200 AD to 1200 AD for the Hautes-Fagnes plateau (East Belgium) : based on pollen grains, testate amoebae, and humification analyses
Beghin, Jérémie ULg; Fagel, Nathalie ULg; Gerrienne, Philippe ULg et al

Poster (2012, September 12)

Several peat cores were extracted from the Misten bog, on the Hautes-Fagnes plateau (East Belgium). Analyses of pollen grains, testate amoebae and the degree of peat humification have been standardised ... [more ▼]

Several peat cores were extracted from the Misten bog, on the Hautes-Fagnes plateau (East Belgium). Analyses of pollen grains, testate amoebae and the degree of peat humification have been standardised and combined into a palaeo-hydro-climatic model from 200 AD to 1200 AD. The reconstruction shows 9 distinctive phases of near-surface water tables, which may be used to infer changes in the atmospheric water balance of eastern Belgium during the Subatlantic stage. [less ▲]

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See detailWavelet Spectrum Estimation under Chronology Uncertainties Application to Dust Flux Data from Belgian Fagnes
Lenoir, Guillaume; Allan, Mohammed ULg; Crucifix, Michel et al

Poster (2012, July)

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See detailMid and late Holocene dust deposition in Western Europe: The Misten peat bog (Hautes Fagnes - Belgium)
Allan, Mohammed ULg; Fagel, Nathalie ULg; Le Roux, Gael et al

Poster (2012, June 28)

The Misten peat bog representing 7.5 m of peat accumulation in the Hautes-Fagnes Plateau, Belgium, provides a record of Rare Earth Elements (REE) deposition since more than 7000 years. The analyses of REE ... [more ▼]

The Misten peat bog representing 7.5 m of peat accumulation in the Hautes-Fagnes Plateau, Belgium, provides a record of Rare Earth Elements (REE) deposition since more than 7000 years. The analyses of REE and lithogenic element concentrations, as well as the Nd isotopes, were performed by HR-ICP-MS and MC-ICP-MS, respectively in peat layers previously dated by 210Pb and 14C. REE concentration variations in peat samples are correlated with Ti, Zr and Sc that are lithogenic conservative elements, suggesting that REE are immobile in the studied peat bogs [1] and can be used as tracers of dust deposition. Peat humification, C/N ratio, ash content and bulk density were used to evaluate hydroclimatic conditions. The Nd values show large variability, between +1 to –22, identifying three major sources of dusts falling into the peat: local soils, distal volcanic and desert particles. More recently, industrial emissions provide a fourth source of dusts [2], which is also clearly recorded in the last 200 years of the Misten peat profile. [less ▲]

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See detailMid and late Holocene dust deposition in Western Europe: The Misten peat bog (Hautes Fagnes - Belgium)
Allan, Mohammed ULg; Le Roux, Gael; Piotrowska, Natalia et al

Poster (2012, June)

Multi-proxy climate recorded from peatlands have been used to tracer the climate change during the Holocene. The initiation of peatland may be related to a change to colder and or wetter climate, and the ... [more ▼]

Multi-proxy climate recorded from peatlands have been used to tracer the climate change during the Holocene. The initiation of peatland may be related to a change to colder and or wetter climate, and the variations in peat composition reflect changes in precipitation and temperature. Peat has been used as an archive to reconstruct climate change over the Holocene (e.g., Shotyk et al., 1998; Sapkota et al., 2006). To characterize the climate in Belgium, a 570 cm-long core from Misten peat bog was studied. Several radiocarbon ages allow to define an accurate age model, the peat core represents 5500 years of record. The analyses of REE and lithogenic element contents, as well as the Nd isotopes, were performed by HR-ICP-MS and MC-ICP-MS. Peat humification, C/N ratio, ash content and bulk density were used to evaluate local hydroclimatic conditions. The dust deposition ranges from 0.03 to 4 g m -2 yr -1. As a first observation the highest rates of atmospheric dust deposition correspond to cold periods. The Nd values show large variability, between +1 to –22, identifying three major sources of dusts falling into the peat: local soils, distal volcanic and desert particles. Further studies are in progress to better identify the main forcing factor on the evolution of the atmospheric dust deposition over the Holocene. [less ▲]

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See detailMineralogical and Chemical Characterizations of Natural Clays from NW Cameroon
Mache, Jacques Richard ULg; Fagel, Nathalie ULg; Njoya, André

Poster (2012, June)

In this study physical and chemical characterization of seven clay samples from Cameroon is reported. The various analysis show that the main clay mineral in all samples is smectite with a small amount of ... [more ▼]

In this study physical and chemical characterization of seven clay samples from Cameroon is reported. The various analysis show that the main clay mineral in all samples is smectite with a small amount of kaolinite; some non clay minerals as cristobalite, K-feldspars, plagioclase, ilmenite and quartz are also present. The Cation Exchange Capacities range from 24.2 to 62.0 meq/100g. The specific surface area range from 58 to 123 m2/g. The chemical composition of the clays is dominated by SiO2, Al2O3 and Fe2O3 whereas MgO and Na2O are present only in small quantities. [less ▲]

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See detailPhysico-chimie et minéralogie des argiles de Bana (Ouest, Cameroun)
Mache, Jacques Richard ULg; Fagel, Nathalie ULg; SIGNING, Pierre

Poster (2012, May 15)

Dans le but de contribuer à la valorisation des géoressources, notamment les matériaux argileux du Cameroun, nous avons dans ce travail procédé à la caractérisation minéralogique et physico-chimique des ... [more ▼]

Dans le but de contribuer à la valorisation des géoressources, notamment les matériaux argileux du Cameroun, nous avons dans ce travail procédé à la caractérisation minéralogique et physico-chimique des argiles récoltées dans la région de Bana. Pour cela diverses méthodes et moyens d’identification ont été utilisés, notamment la diffraction des rayons X (DRX), l’analyse chimique, la spectroscopie infrarouge, la microscopie électronique à balayage, l’analyse thermique, l’analyse granulométrique, la détermination des capacités d’échange cationique et la détermination de la surface spécifique. Les résultats de cette étude ont montré que les argiles de Bana sont formées principalement de smectite, kaolinite et talc comme minéraux argileux. Les minéraux non argileux associés sont l’anatase, le quartz, le feldspath, la goethite et l’hématite. Les observations au microscope électronique à balayage sont conformes avec la nature smectique de ces matériaux (Figure 1). Les capacités d’échange cationique (comprises entre 40 et 57 méq/100g) et les surfaces spécifiques (comprises entre 50 et 68 m2) sont également dans les moyennes mesurées pour des argiles smectiques (Morgan et al.,1985; Van Olphen et Fripiat,1979). Le test de saturation au lithium (test de Green Kelly - Lim et Jackson, 1986) a permis d’établir que la montmorillonite était le minéral smectique de ces argiles. Le couplage des analyses chimiques et minéralogiques permet une quantification minéralogique moyenne: 74% de Montmorillonite; 6% de Kaolinite; 8% de talc. Les matériaux de Bana sont riche en smectite et peuvent dont être valorisés dans les domaines tels que l’absorption, l’agriculture ou de l’imperméabilisation des sols. [less ▲]

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See detailCaractérisation des dépôts argileux de Nanga-Eboko (Centre Cameroun):Aptitude dans la production des briques cuites
Nzeukou Nzeugang, Aubin ULg; Medjo Eko, Robert; Fagel, Nathalie ULg et al

Poster (2012, May 14)

Cette étude entre dans le cadre de la valorisation des argiles industrielles du Cameroun avec pour perspective la mise sur pied des unités de production industrielles des matériaux de construction ... [more ▼]

Cette étude entre dans le cadre de la valorisation des argiles industrielles du Cameroun avec pour perspective la mise sur pied des unités de production industrielles des matériaux de construction (Briques et tuiles cuites). Ainsi, dans ce travail, nous avions à estimé à 9-12)x105 m3 la quantité d’argile que regorge la localité Nanga-Eboko (Région du Centre Cameroun). Sur le plan chimique, l’argile contient: ~70% silice, ~ 12% alumine, ~ 7% fer) et sur le plan minéralogique :~ 40-60% kaolinite, ~20-25% quartz et illite ~12% Feldspath et smectite sont présents (9 et 5% resp.). L'observation microscopique et l’IR montrent des formes irrégulières de kaolinite mal cristallisée, caractéristique des argiles d'origine sédimentaire. Les propriétés des briques (800-1100°C) montrent un retrait linéaire élevé (3-11%), un taux d'absorption d'eau faible (17-8%) et des valeurs de compression (11-50 Mpa). Au vu de la plasticité élevée (24%) de ces argiles, de leurs particules fines (<2 µm) >70%, l'ajout de dégraissant (sable ou latérite) est nécessaire pour une bonne optimisation du mélange afin d'avoir un produit fini de qualité pour la construction de bâtiments. [less ▲]

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See detailLast millenium environmental changes in Lake Bertrand sediments, Chilean Patagonia
Sacré, Vincent ULg; Fagel, Nathalie ULg; Schmidt, Sabine et al

Poster (2012, April 23)

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See detailUsing the N/C ratio to correct bulk radiocarbon ages from lake sediments: Insights from Chilean Patagonia
Bertrand, Sébastien; Arraneda, A.; Vargas, P. et al

in Quaternary Geochronology (2012), 12

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See detailVolcano- and climate-driven changes in atmospheric dust sources and fluxes since the Late Glacial in Central Europe
Le Roux, Gael; Fagel, Nathalie ULg; De Vleeschouwer, François et al

in Geology (2012)

Atmospheric dusts are an important part of the global climate system, and play an important role in the marine and terrestrial bio- geochemical cycles of major and trace nutrient elements. A peat bog ... [more ▼]

Atmospheric dusts are an important part of the global climate system, and play an important role in the marine and terrestrial bio- geochemical cycles of major and trace nutrient elements. A peat bog record of atmospheric deposition shows considerable variation in dust deposition during the past 15 k.y., with abrupt changes in fl uxes at 12, 9.2, 8.4, 7.2, and 6 cal. kyr B.P. Using Nd isotopes and rare earth ele- ments, it is possible to clearly distinguish between volcanic inputs and those driven by climate change, such as the long-term aridifi cation of the Sahara and regional erosion due to forest clearing and soil cultiva- tion activities. Our results indicate that a major dust event in North Africa and Europe preceded the 8.2 kyr B.P. cold event by 200 yr. This dust event may have played an active role in the following climate cooling of the 8.2 kyr B.P. event. Nd isotope evidence also indicates a relatively slow change in dust regime over Europe from 7 to 5 kyr B.P. due to Sahara expansion. These fi ndings show that the inorganic frac- tion in high-resolution peat records can provide remarkably sensitive indicators of dust load and sources. Our study supports the priority to better identify the impact of dust loading during the Holocene in terms of direct and indirect impacts on environmental and climate changes. [less ▲]

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See detailPaleoseismic record obtained by coring a lacustrine sag-pond along the North Anatolian Fault (Turkey)
Hubert, Aurelia ULg; Avsar, Ulas; El Ouahbi, Meriam et al

in Annals of Geophysics = Annali di Geofisica (2012)

Shallow lakes along minor structural bends or discontinuities of strike-slip fault are not usually paleoseismological target sites. In the present study we show that a 2m deep, 700m long lake crosscut by ... [more ▼]

Shallow lakes along minor structural bends or discontinuities of strike-slip fault are not usually paleoseismological target sites. In the present study we show that a 2m deep, 700m long lake crosscut by the North Anatolian Fault contain a reliable paleoseimological record obtain through coring. The North Anatolian Fault, a major strike-slip fault in Turkey last ruptured across the Asacipetecik Lake in 1939 with a slip of about 6 m. Seismic lines still shows remains of the fault ruptures forming minor 10 cm high scarps across the lake. Collected short cores show a set of sedimentary sequences composed of three different units. The lower unit, dark and fibrous, is similar to the present sedimentation at the top of the core. The strongly disturbed and whitish top unit 1 has anomalous organic matter content, grain size and mineralogy. The unit 2 is intermediate in between unit 1 and 3. The present stratigraphy is related to earthquake shaking inducing (1) sediment resuspension; (2) reworking of sediments coming from co-seismic scarps and lake margins; (3) increase in sedimentary runoff into the lake. The 2.5 m long core comprises 4 sequences, and thus 4 sedimentary events. Cesium and Lead data obtained in Boes et al. (2009) imply that Event 1 was triggered by the 1939 M=7.9 Erzincam Earthquake. Radiocarbon age dating suggest that Events 3 and 4 are initiated by the 1254 and the 1045 historical earthquake. Event 2 may correspond to the 1668 earthquake documented in paleoseimological trenches a few kilometers to the east. [less ▲]

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See detailValorisation de l'argile de Bana (Ouest-Cameroun) dans la décoloration d'une huile végétale alimentaire
Mache, Jacques Richard ULg; Fagel, Nathalie ULg; Signing, Pierre

Scientific conference (2011, December 02)

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See detail2500 years record of trace element metal in the Misten peat bog (Hautes Fagnes), Belgium
Allan, Mohammed ULg; Fagel, Nathalie ULg; le roux, Gael et al

Poster (2011, April 08)

The Misten peat bog provides a record of atmospheric deposition in the Hautes Fagnes Plateau (East Belgium). A composite 185cm core (W01/01b) was studied for its trace metal content (TM) and its lead ... [more ▼]

The Misten peat bog provides a record of atmospheric deposition in the Hautes Fagnes Plateau (East Belgium). A composite 185cm core (W01/01b) was studied for its trace metal content (TM) and its lead isotopic signature. The peat bog accumulation allows following the history of atmospheric TM deposition during the last 2500 years. TM enrichment factors coupled with a continuous decrease in 206Pb/204Pb, 207Pb/204Pb,208Pb/204Pb isotopic ratios from 494-732AD to1969-1977 AD evidence the increasing importance of TM released by anthropogenic activities. The highest concentrations of TM are found near the surface of the bog; at depths from 30 to 19 cm. Historical records of Cu, Zn, As, Sb, and Pb atmospheric flux during the Industrial Revolution and pre-industrial periods were derived. Maximum fluxes (up to 7.3, 89, 2.4, 1.5, and 116 mg.m-2.y-1, respectively) occurred in peat layers dated from 1619-1877AD to 1992-2000AD, reflecting anthropogenic emissions from diverse sources such as mining, coal combustion, and emissions from the use of leaded gasoline. The TM enrichment factors also increased significantly during the Industrial Revolution until a reduction at the end of the 70’S due to the progressive abolition of the leaded gasoline. [less ▲]

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See detailAtmospheric mercury deposition during the last 1500 years in We Europe: The Misten peat bog record (Hautes Fagnes - Belgium)
Allan, Mohammed ULg; Fagel, Nathalie ULg; De Vleeschouwer, François et al

Poster (2011, April)

The current rate of global atmospheric Hg deposition is approximately three times higher than the preindustrial record and it even increased by a factor of 2-10 in the industrialized regions ... [more ▼]

The current rate of global atmospheric Hg deposition is approximately three times higher than the preindustrial record and it even increased by a factor of 2-10 in the industrialized regions.....()(Hylander and Meili 2003). To determine the extent of such increase, it is necessary to quantify the atmospheric mercury concentration and its temporal variation. For this purpose four 1m Wardenaar peat cores (MIS01W, 04W, 0W5 and 06W) were collected in 2008 in the ombrotrophic Misten bog (Hautes Fagnes Plateau, East Belgium). Mercury was measured using a DMA 80 at the Laboratory of Mechanisms and Transfers in Geology in Toulouse (LMTG, France). The strongest mercury concentrations are measured in the upper half peat record, in a depth interval corresponding to the Industrial Revolution period. Mercury accumulation rate was estimated by applying a coupled 210Pb- 14C age model. The mercury accumulation rate remains relatively small, ranging between 0.9 and 3.3 g.m 2.y 1 during periods corresponding to the decline of Roman Empire and during the Middle Ages. Hg accumulation rate starts to increase when 25 cm, reaching a maximum value (> 115 g.m 2.y 1) at 13.7 cm (i.e.; 1923-1938 AD). Then the values oscillate to reach 9 g.m 2.y 1 at the peat surface (2000-2007AD). In the Misten bog, the evolution of Hg accumulation rate is in agreement with the chronology of other European peat records .......()(Roos-Barraclough et al. 2002). [less ▲]

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See detailHolocene evolution of deep circulation in the northern North Atlantic traced by Sm, Nd and Pb isotopes and bulk sediment mineralogy
Fagel, Nathalie ULg; Mattielli, Nadine ULg

in Paleoceanography (2011), 26

Bulk mineralogy, Sm, Nd and Pb elemental and isotopic compositions of the clay-size fraction of Holocene sediments were analysed in 3 deep North Atlantic cores to trace the particle provenance. The aims ... [more ▼]

Bulk mineralogy, Sm, Nd and Pb elemental and isotopic compositions of the clay-size fraction of Holocene sediments were analysed in 3 deep North Atlantic cores to trace the particle provenance. The aims of the present paper are to identify the origin of the particles driven by deep currents and to reconstruct deep circulation changes over the Holocene in the North Atlantic. The three cores are retrieved in fracture zones; two of them are located in the Island Basin along the gyre of North Atlantic Deep Water, and the third core is located off the present deep circulation gyre in the Labrador Sea. Whereas sedimentary supplies in the Labrador Sea were constantly derived from proximal sources, the geochemical mixing trends in the Iceland Basin samples indicate pronounced changes in the relative contribution of continental margin inputs over the past 6 kyr. Supplies from Western European margin that sharply increased at 6 kyr were progressively diluted by a larger contribution of Scandinavian margins over the last 3 kyr. Changes in composition of the particles imply significant reorganisation of paleocirculation of the deep North Atlantic components in the Eastern basins: mainly reorganisations for both Iceland-Scotland Overflow Water (ISOW) and Norwegian Sea Overflow Water (NSOW). Moreover the unusual Bulk mineralogy, Sm, Nd and Pb elemental and isotopic compositions of the clay-size fraction of Holocene sediments were analysed in 3 deep North Atlantic cores to trace the particle provenance. The aims of the present paper are to identify the origin of the particles driven by deep currents and to reconstruct deep circulation changes over the Holocene in the North Atlantic. The three cores are retrieved in fracture zones; two of them are located in the Island Basin along the gyre of North Atlantic Deep Water, and the third core is located off the present deep circulation gyre in the Labrador Sea. Whereas sedimentary supplies in the Labrador Sea were constantly derived from proximal sources, the geochemical mixing trends in the Iceland Basin samples indicate pronounced changes in the relative contribution of continental margin inputs over the past 6 kyr. Supplies from western European margin that sharply increased at 6 kyr were progressively diluted by a larger contribution of Scandinavian margins over the last 3 kyr. Changes in composition of the particles imply significant reorganisation of paleocirculation of the deep North Atlantic components in the eastern basins: mainly reorganisations for both Iceland-Scotland Overflow Water (ISOW) and Norwegian Sea Overflow Water (NSOW). Moreover the unusual Pb isotopic composition of the oldest sediments from the southern Iceland Basin indicates that distal supplies from Greenland margin were driven into the Iceland Basin, supporting a deep connection between Labrador Sea and Iceland Basin through the Charlie Gibbs Fracture Zone prior the Holocene Transition period. [less ▲]

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