References of "Fagel, Nathalie"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailClimate oscillations evidenced by spectral analysis of Southern Chilean lacustrine sediments: the assessment of ENSO over the last 600 years
Fagel, Nathalie ULg; Boes, X.; Loutre, M. F.

in Journal of Paleolimnology (2008), 39(2), 253-266

The Chilean Lake District (38-42 degrees S) is strongly influenced by Southern westerlies-driven precipitations. At 40 degrees S Lago Puyehue provides high resolution sedimentation rates (similar to 1-2 ... [more ▼]

The Chilean Lake District (38-42 degrees S) is strongly influenced by Southern westerlies-driven precipitations. At 40 degrees S Lago Puyehue provides high resolution sedimentation rates (similar to 1-2 mm/yr) suitable for annual climate reconstruction. Several short and long sediment cores were collected in this lake. Their analysis aim at a better understanding of climate mechanisms related to ENSO in this part of the world. The recognition of ENSO related periodicities and their stability is studied through the analysis of two short varved cores collected from underflow and interflow key sites. According to varve chronology controlled by Cs-137 and Pb-210 profiles and chronostratigraphical markers, the short core from underflow site (PU-I) spans 294 +/- 18 years and the core in the interflow site (PU-II) covers 592 +/- 9 years. Several methods of spectral analysis were applied on the total varve thickness to identify potential periodicities in the signal. Blackman-Tuckey, Maximum Entropy, Multi-Taper Methods (MTM) and singular spectrum analysis were applied on the whole record. In addition, evolutive MTM and wavelet analyses allow to identify temporal influence of some periodicities. In the PU-I studied interval (AD 1700-2000), a period at similar to 3.0 years appears in a large part of the interval, mostly in the recent part. Periods at similar to 5.2 and similar to 23 years also show up. PU-II record (AD 1400-2000) displays the most robust periodicities at around 15, 9, 4.4, 3.2 and 2.4 years. These periodicities are in good agreement with the sub-decadal periods identified by Dean and Kemp (2004) and linked to the El Nino Southern Oscillation and the Pacific Decadal Oscillation. Differences in the recorded periodicities between PU-I and PU-II sites are consistent with different sedimentation processes in the lake. According to climate instrumental data for the last 20 years, varves in PU-I site are mostly related to fluvial dynamics and regional climate factors, i.e., precipitation, temperature and wind. In PU-II site, varves increment is related to both regional and global climate forcing factors, i.e., El Nino Southern Oscillation. The evolutive MTM analysis and the wavelet analysis suggest a striking break in the periodicities at around AD 1820. Finally relationships between El Nino and longer term climate phase like the Little Ice Age (LIA) are also assessed. [less ▲]

Detailed reference viewed: 54 (3 ULg)
Full Text
Peer Reviewed
See detailRelationships between southern Chilean varved lake sediments, precipitation and ENSO for the last 600 years
Boes, Xavier; Fagel, Nathalie ULg

in Journal of Paleolimnology (2008), 39(2), 237-252

In this paper, the relationships between paleo-precipitation and the regional influence of El Nino Southern Oscillation (ENSO) in South America are assessed from a high-resolution calendar varve-thickness ... [more ▼]

In this paper, the relationships between paleo-precipitation and the regional influence of El Nino Southern Oscillation (ENSO) in South America are assessed from a high-resolution calendar varve-thickness record. Two short laminated sediment cores (53 and 61 cm length) from Lago Puyehue (40 degrees S) are analysed by continuous varve measurements through the last 600 years. The calendar varve years are determined by the occurrence of graded planktonic-rich layers. The annual sediment accumulation rates are reconstructed by using the standard varve-counting methods on thin sections. The 1980-2000 varve-thickness record is interpreted in terms of climate through correlation with limnological and local monthly instrumental climate databases. The comparison between the standardized varve thickness with the instrumental records reveals a strong correlation (r = 0.75, p = 0.07) between the total varve thickness and the austral autumn/winter precipitation. We argue that strong austral winter winds and precipitation are the forcing factors for the seasonal turn-over and phytoplankton increase in the lake sediments. During strong El Nino events the precipitation and the winds decrease abnormally, hence reducing the thickness of the biogenic sediments deposited after the winter turn-over. Our results show one significant regional maximum peak of winter precipitation (>900 mm) in the mid 20th century and a significant period with lower winter precipitation (<400 mm) before the 15th century, i.e., the late Medieval Warm Period. The first peak in the mid 20th century is confirmed by the regional precipitation database. The influence of ENSO cycles over the last 600 years is assessed by spectral analysis in Fagel et al. (2007). The possible influence of the regional volcanism and/or the seismic activity on the local climate record is also discussed. [less ▲]

Detailed reference viewed: 30 (3 ULg)
Full Text
Peer Reviewed
See detailLate Quaternary climatic changes in southern Chile, as recorded in a diatom sequence of Lago Puyehue (40 degrees 40 ' S)
Sterken, Mieke; Verleyen, Elie; Sabbe, Koen et al

in Journal of Paleolimnology (2008), 39(2), 219-235

A late Quaternary diatom stratigraphy of Lago Puyehue (40 degrees 40'S, 72 degrees 28'W) was examined in order to infer past limnological and climatic changes in the South-Chilean Lake District. The ... [more ▼]

A late Quaternary diatom stratigraphy of Lago Puyehue (40 degrees 40'S, 72 degrees 28'W) was examined in order to infer past limnological and climatic changes in the South-Chilean Lake District. The diatom assemblages were well preserved in a 1,122 cm long, C-14-dated sediment core spanning the last 17,900 years, and were in support of an early deglaciation of Lago Puyehue. The presence of a short cold spell in South Chile, equivalent to the Younger Dryas event in the Northern Hemisphere, the Antarctic Cold Reversal in Antarctica, or the Huelmo-Mascardi event in southern South America, was not clearly evidenced in the diatom data, although some climate instability may have occurred between 13,400 and 11,700 cal. yr. BP, and a relatively long period (between 16,850 and 12,810 cal. yr. BP) with low absolute abundances and biovolumes could be tentatively interpreted as a period of low rainfall and/or temperatures. An increase in the moisture supply to the lake was tentatively inferred at 12,810 cal. yr. BP. After 9,550 cal. yr. BP, inferred stronger and longer persisting summer stratification, may have been the result of the higher temperatures associated with an early-Holocene thermal optimum. The mid-Holocene appeared to be characterized by a decrease in precipitation, culminating around 5,000 cal. yr. BP, and rising again after 3,000 cal. yr. BP, likely associated with a previously documented lowered frequency and amplitude of El Nino events. An increase in precipitation during the late Holocene (3,000 cal. yr. BP-present) might have marked subsequent increased frequency of El Nino occurrences, leading to drier summers and slightly moister winters in the area. [less ▲]

Detailed reference viewed: 40 (8 ULg)
Full Text
Peer Reviewed
See detailClimate variability of southern Chile since the Last Glacial Maximum: a continuous sedimentological record from Lago Puyehue (40 degrees S)
Bertrand, Sebastien; Charlet, Francois; Charlier, Bernard ULg et al

in Journal of Paleolimnology (2008), 39(2), 179-195

This paper presents a multi-proxy climate record of an 11 m long core collected in Lago Puyehue (southern Chile, 40 degrees S) and extending back to 18,000 cal yr BP. The multi-proxy analyses include ... [more ▼]

This paper presents a multi-proxy climate record of an 11 m long core collected in Lago Puyehue (southern Chile, 40 degrees S) and extending back to 18,000 cal yr BP. The multi-proxy analyses include sedimentology, mineralogy, grain size, geochemistry, loss-on-ignition, magnetic susceptibility and radiocarbon dating. Results demonstrate that sediment grain size is positively correlated with the biogenic sediment content and can be used as a proxy for lake paleoproductivity. On the other hand, the magnetic susceptibility signal is correlated with the aluminium and titanium concentrations and can be used as a proxy for the terrigenous supply. Temporal variations of sediment composition evidence that, since the Last Glacial Maximum, the Chilean Lake District was characterized by three abrupt climate changes superimposed on a long-term climate evolution. These rapid climate changes are: (1) an abrupt warming at the end of the Last Glacial Maximum at 17,300 cal yr BP; (2) a 13,100-12,300 cal yr BP cold event, ending rapidly and interpreted as the local counterpart of the Younger Dryas cold period, and (3) a 3,400-2,900 cal yr BP climatic instability synchronous with a period of low solar activity. The timing of the 13,100-12,300 cold event is compared with similar records in both hemispheres and demonstrates that this southern hemisphere climate change precedes the northern hemisphere Younger Dryas cold period by 500 to 1,000 years. [less ▲]

Detailed reference viewed: 247 (9 ULg)
Full Text
Peer Reviewed
See detailA 17,900-year multi-proxy lacustrine record of Lago Puyehue (Chilean Lake District): introduction
De Batist, Marc; Fagel, Nathalie ULg; Loutre, Marie-France et al

in Journal of Paleolimnology (2008), 39(2), 151-161

This paper introduces the background and main results of a research project aimed at unravelling the paleolimnological and paleoclimatological history of Lago Puyehue (40 degrees S, Lake District, Chile ... [more ▼]

This paper introduces the background and main results of a research project aimed at unravelling the paleolimnological and paleoclimatological history of Lago Puyehue (40 degrees S, Lake District, Chile) since the Last Glacial Maximum (LGM), based on the study of several sediment cores from the lake and on extensive fieldwork in the lake catchment. The longest record was obtained in an 11-m-long piston core. An age-depth model was established by AMS C-14 dating, Pb-210 and Cs-237 measurements, identification of event-deposits, and varve-counting for the past 600 years. The core extends back to 17,915 cal. yr. BP, and the seismic data indicate that an open-lake sedimentary environment already existed several thousands of years before that. The core was submitted to a multi-proxy analysis, including sedimentology, mineralogy, grain-size, major geochemistry and organic geochemistry (C/N ratio, delta C-13), loss-on-ignition, magnetic susceptibility, diatom analysis and palynology. Along-core variations in sediment composition reveal that the area of Lago Puyehue was characterized since the LGM by a series of rapid climate fluctuations superimposed on a long-term warming trend. Identified climate fluctuations confirm a.o. the existence of a Late-Glacial cold reversal predating the northern-hemisphere Younger Dryas cold period by 500-1,000 years, as well as the existence of an early southern-hemisphere Holocene climatic optimum. Varve-thickness analyses over the past 600 years reveal periodicities similar to those associated with the El Nino Southern Oscillation and the Pacific Decadal Oscillation, as well as intervals with increased precipitation, related to an intensification of the El Nino impact during the southern-hemisphere equivalent of the Little Ice Age. [less ▲]

Detailed reference viewed: 597 (5 ULg)
Full Text
Peer Reviewed
See detailGeochemical and Pb isotopic signature of peaty sediments from central-south Chile: Identification of particle supplies over the Holocene
De Vleeschouwer, François ULg; Ibanez, Maud; Mattielli, Nadine et al

in Journal of the Chilean Chemical Society [=JCCS] (2008), 53(3), 1640-1649

Two cores from tephra rich peat soils of the Chilean Lake District were investigated for mineral source and potential anthropogenic impact using elemental geochemistry, including rare earth elements, and ... [more ▼]

Two cores from tephra rich peat soils of the Chilean Lake District were investigated for mineral source and potential anthropogenic impact using elemental geochemistry, including rare earth elements, and lead isotopes. The dominant particle source to the area are the Trumaos which are the local ando soils derived from the weathering of volcanic deposits. In Galletue, although short term events of enhanced particle inputs occur, elemental and isotopic signatures show that the Trumaos are the only particle source to the area. In San Pablo de Tregua, punctual events of crustal particle inputs are recorded in Pb enrichment factors and isotopic profiles, reflecting a long range crustal involvement. This site also records the inception of the anthropogenic in the area in recent samples of which Pb enrichment factors and lead isotopic signatures shift drastically. [less ▲]

Detailed reference viewed: 40 (4 ULg)
Full Text
Peer Reviewed
See detailLong term mobilisation of chemical elements in tephra-rich peat (NE Iceland)
De Vleeschouwer, François ULg; Lanoe, Brigitte Van Vliet; Fagel, Nathalie ULg

in Applied Geochemistry (2008), 23(12), 3819-3839

This paper presents geochemical profiles of a tephra-bearing minerotrophic peat column from NE-Iceland obtained using various elemental analyses of the solid phase and the pore water. The influence of ... [more ▼]

This paper presents geochemical profiles of a tephra-bearing minerotrophic peat column from NE-Iceland obtained using various elemental analyses of the solid phase and the pore water. The influence of tephra grain size, thickness and composition of each tephra on the peat geochemistry was investigated. Interpretations are supported by a statistical approach, in particular by autocorrelation, and by microscopy observations. Minerotrophic peat geochemistry may be strongly dependent upon post-depositional mobilization and possible leaching of elements as demonstrated by Fe and trace metal concentration profiles. Chemical elements, and more specifically potentially harmful metals, can be slowly leached out of volcanic falls during their weathering and re-accumulate downwards. It is emphasised that a tephra deposit can act as an active geochemical barrier, blocking downward elemental movements and leading to the formation of enriched layers. In this study, the formation of poorly amorphous Fe phases above the Hekla 3 tephra is shown. These poorly crystalline Fe phases scavenged Ni. (c) 2008 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 44 (3 ULg)
Full Text
Peer Reviewed
See detailRoman road pollution assessed by elemental and lead isotope geochemistry in East Belgium
Renson, Virginie; Fagel, Nathalie ULg; Mattielli, Nadine et al

in Applied Geochemistry (2008), 23(12), 3253-3266

The ability of inorganic geochemistry to record environmental change and especially human impact has been evidenced by several studies across Europe, especially in peat, where it is possible to record the ... [more ▼]

The ability of inorganic geochemistry to record environmental change and especially human impact has been evidenced by several studies across Europe, especially in peat, where it is possible to record the impact of agriculture, mining and other industries. However, despite the numerous investigations on the impact of ancient human activities such as ore mining and smelting, little attention has been paid to geochemistry as a tool to solve problems of palaeopollution in the surroundings of archaeological sites. This paper presents geochemical evidence of the impact of a possible early Roman road built in SE Belgian peatland. Increased Zn and Pb concentrations suggest that Pb-Zn ores were transported on the road, Lead isotope analyses suggest that these ores are locally derived, being compatible with those found in the nearby Pb-Zn ore deposits from East Belgium. Present results provide direct evidence that East Belgian Pb-Zn ores were already being mined during Roman times, i.e. earlier than previously suspected (i.e. 14th century) and that Zn appears to be relatively immobile here. On a broader scale, it also demonstrates that such an early road already had an impact on the environment in terms of metal pollution. This paper enlarges on the range of possibilities offered by geochemistry in the field of geoarchaeology. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 61 (5 ULg)
Full Text
See detailHolocene Records of Aerosols in Continental Environments (HoRACE)
Le Roux; De Vleeschouwer, F.; Cherbukin et al

Conference (2008)

Detailed reference viewed: 4 (1 ULg)
Full Text
See detailDevelopment of a "pre-anthropogenic" peat standard for geochemical, paleo-environmental and archaeological investigations
Le Roux; De Vleeschouwer, F.; Cheburkin et al

Poster (2008)

Detailed reference viewed: 1 (0 ULg)
Full Text
See detailRecent climatic instability in Poland and effect of Little Ice Age on human activities
De Vleeschouwer, F.; Lamentovicz, M.; Piotrowska, N. et al

Poster (2008)

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailDevelopment and application of high-resolution petrography on resin-impregnated Holocene peat columns to detect and analyse tephras, cryptotephras, and other materials
De Vleeschouwer, François ULg; van Vliet-Lanoe, Brigitte; Fagel, Nathalie ULg et al

in Quaternary International (2008), 178

We describe the potential for high-resolution detection, observation and chemical analysis of tephras and cryptotephras in freeze-dried and resin-impregnated peat sections. Special attention is drawn to ... [more ▼]

We describe the potential for high-resolution detection, observation and chemical analysis of tephras and cryptotephras in freeze-dried and resin-impregnated peat sections. Special attention is drawn to tephra grain alteration products, sensitive to standard lab treatment, but preserved using an impregnation technique developed here. Resulting blocks and thin sections provide a continuous archive of tephras that can be investigated through a wide range of non-destructive techniques encompassing polarising and fluorescence microscopy, scanning electron microscopy with/without elemental analysis, and XRF-based core scanning. (c) 2007 Elsevier Ltd and INQUA. All rights reserved. [less ▲]

Detailed reference viewed: 34 (1 ULg)
Full Text
See detailTraces of the last earthquake sequence (1939-1944) along NAF from lacustrine sediments.
Avsar, U.; Boes, X.; Hubert-Ferrari, A. et al

Poster (2008)

Detailed reference viewed: 5 (0 ULg)
Full Text
See detailSedimentological Fingerprints of Recent Earthquakes in Lake Sediments: A Case Study on the North Anatolian Fault (NAF), Turkey
Avsar, U.; Boes, X.; Hubert-Ferrari, A. et al

Poster (2008)

Detailed reference viewed: 13 (2 ULg)
See detailHolocene instabilities in GIN sea overflows based on mineralogical and Nd/Pb isotopic sedimentary records
Simon, Q.; Fagel, Nathalie ULg; Jennings, A. et al

Poster (2008)

Detailed reference viewed: 10 (2 ULg)
See detailLacustrine record of Late Pleistocene and Holocene climate evolution, volcanism and seismic activity in Lake Puyehue (Chilean Lake District)
De Batist, M.; Fagel, Nathalie ULg; Loutre, M. F. et al

Book published by Journal of Paleolimnology (2008)

Detailed reference viewed: 8 (2 ULg)