References of "Fagel, Nathalie"
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See detailIndustrial potentiality of alluvial clays deposits from Cameroon: influence of lateritic clayey admixture for fired bricks production.
Nzeukou Nzeugang, A.; Kamgang Kabeyene, V.; Medjo Eko, R. et al

in Journal of Minerals and Materials Characterization and Engineering (2013)

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See detailCambios ambientales del último milenio en sedimentos lacustres del Lago Thompson, Patagonia Chilena Norte
Sacré, Vincent ULg; Fagel, Nathalie ULg; Leclercq, Louis ULg et al

Poster (2012, October 25)

Este estudio se enfoca en un análisis multiproxy de un testigo sedimentario del Lago Thompson (area 1 km2; 751 masl ; 45°38’S 72°47’W) obtenido en 2008 (LT08-E, 130 cm), con el objetivo de documentar la ... [more ▼]

Este estudio se enfoca en un análisis multiproxy de un testigo sedimentario del Lago Thompson (area 1 km2; 751 masl ; 45°38’S 72°47’W) obtenido en 2008 (LT08-E, 130 cm), con el objetivo de documentar la variabilidad climática durante el último milenio en la Patagonia Chilena Norte y su impacto sobre el ambiente. El modelo de datación se basó en cinco fechados de 14C. Los resultados de 210Pb y 137 Cs no permitieron estimar la tasa de sedimentación para la parte superficial del núcleo. El lago Thompson esta caracterizado por una pequeña cuenca de suaves pendientes y sus sedimentos están dominados por limo arcilloso y partículas amorfas (principalmente diatomeas). Esto último es sustentado por la relación atómica de carbono/nitrógeno (C/N) que indica el origen fitoplanctónico del sedimento (8-10). Los perfiles de rayos –X, susceptibilidad magnética y LOI 550ºC evidencian dos depósitos volcánicos en 1410-1440 y 1780-1790 AD. Los perfiles de C/N y sílice biogénica (SiB) sugieren una alta productividad durante un periodo equivalente a la Pequeña Edad del Hielo (1650-1850 AD), con una máxima intensidad durante ~1800 AD. Desde 1850 AD hasta la actualidad, los perfiles de LOI 550ºC y SiB evidencian una reciente eutrofización y aumento del nivel del lago (asociado con aumento de temperaturas y humedad). Además, los perfiles de SiB presentan una correlación inversa con las temperaturas reconstruidas por anillos de árboles en la Patagonia. El contenido de diatomeas es dominado por especies planctónicas (Aulacoseira sp. y Cyclotella sp.), mientras que taxa bentónicos no muestran una buena diversificación en comparación a otros lagos de la Patagonia. La abundancia de diatomeas muestra respuestas específicas a los depósitos volcánicos con una disminución de Aulacoseira sp.. La relación planctónica/bentónica permite identificar dos periodos de alto y bajo nivel del lago coincidiendo con fases húmedas y secas de la Pequeña Edad de Hielo (1200-1650 y 1650-1850 AD). La realización de análisis sedimentológicos, geoquímicos y de microfósiles permitiría una mejor caracterización de los modelos de depositación del sedimento (impregnación del núcleo sedimentario) y de la interacción entre depósitos volcánicos y diatomeas. Agradecimientos a Fondecyt Nº1070508, FNRS 1360 2007-2010 y ULg CFRA 1060 2009-2010. [less ▲]

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See detailComparing the paleoseismic record obtained by coring a sag-pond and by classical trenching along the eastern segment of the North Anatolian Fault
Hubert, Aurelia ULg; Avsar, Ulas; Fraser, Jeef et al

Conference (2012, October)

Shallow lakes along minor structural bends or discontinuities of strike-slip fault are not usually paleoseismological target sites. In the present talk 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 talk we show that a 2m deep, 700m long lake crosscut by the eastern segment of the North Anatolian Fault contains a reliable paleoseimological record obtained through coring. The North Anatolian Fault, a major strike-slip fault in Turkey, last ruptured across the Aşağıtepecik Lake in 1939 with a slip of about 6 m. Seismic lines still show remains of the fault rupture forming minor scarps across the lake. Collected short cores display a set of sedimentary sequences. Each sequence is composed of similar organic rich sedimentary units. The lower unit is dark and fibrous, and is similar to the present sedimentation at the top of the core. The upper unit is disturbed and has anomalous organic matter content, grain size and mineralogy. It is interpreted as an earthquake induced sedimentary event. The 2.5 m long AT2007LG core comprises four sequences, and four sedimentary events. Radiogenic 210Pb and 137Cs data obtained in Boes et al. (2009) imply that the shallowest event 1 was triggered by the 1939 M=7.9 Erzincan earthquake. Radiocarbon dating suggest that events 2 and 4 were initiated by the 1668 and 1254 historical earthquakes. The event 3 does not correspond to a large historical earthquake on the NAF. The record can be compared to a classical paleoseismological study located about 2.5 km more to the east. The investigation comprised three paleoseismic trenches located along about 2km of the principal fault strand. Trench T1 revealed clear evidence for one earthquake interpreted to be the 1939 Erzincan earthquake. Trench T2 revealed evidence of three earthquakes. Trench T3 revealed a record of colluvial wedges that interfinger with fine-grained inter-fan deposits. We interpreted a sequence of six earthquake event horizons including the 1939 Erzincan earthquake. The first three earthquakes are correlated to historical earthquakes in A.D. 1668, 1254, 499 and two further events were identified at 881 – 673 B.C. and 1406 – 1291 B.C. (2σ age ranges). By comparing all available earthquake timing studies,we conclude that the 1939 earthquake segment does not always rupture in unison. [less ▲]

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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)

Detailed reference viewed: 55 (7 ULg)