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Cartier R., Sylvestre Florence, Pailles C., Sonzogni C., Couapel Martine, Alexandre A., Mazur J. C., Brisset E., Miramont C., Guiter F. (2019). Diatom-oxygen isotope record from high-altitude Lake Petit (2200 m a.s.l.) in the Mediterranean Alps : shedding light on a climatic pulse at 4.2 ka. Climate of the Past, 15 (1), 253-263. ISSN 1814-9324

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Lien direct chez l'éditeur doi:10.5194/cp-15-253-2019

En Libre Accès sur HAL https://hal.archives-ouvertes.fr/hal-02010676

Titre
Diatom-oxygen isotope record from high-altitude Lake Petit (2200 m a.s.l.) in the Mediterranean Alps : shedding light on a climatic pulse at 4.2 ka
Année de publication2019
Type de documentArticle référencé dans le Web of Science WOS:000458104000002
AuteursCartier R., Sylvestre Florence, Pailles C., Sonzogni C., Couapel Martine, Alexandre A., Mazur J. C., Brisset E., Miramont C., Guiter F.
SourceClimate of the Past, 2019, 15 (1), p. 253-263. ISSN 1814-9324
RésuméIn the Mediterranean area, the 4.2 ka BP event is recorded with contrasting expressions between regions. In the southern Alps, the high-altitude Lake Petit (Mercantour Massif, France; 2200 a.s.l.) offers pollen and diatom-rich sediments covering the last 4800 years. A multi-proxy analysis recently revealed a detrital pulse around 4200 cal BP due to increasing erosion in the lake catchment. The involvement of a rapid climate change leading to increasing runoff and soil erosion was proposed. Here, in order to clarify this hypothesis, we measured the oxygen isotope composition of diatom silica frustules (delta O-18(diatom)) from the same sedimentary core. Diatoms were analysed by laser fluorination isotope ratio mass spectrometry after an inert gas flow dehydration. We additionally enhanced the accuracy of the age-depth model using the Bacon R package. The delta O-18(diatom) record allows us to identify a 500-year time lapse, from 4400 to 3900 cal BP, where delta O-18(diatom) reached its highest values (> 31 parts per thousand). delta O-18(diatom) was about 3 parts per thousand higher than the modern values and the shifts at 4400 and 3900 cal BP were of similar amplitude as the seasonal delta O-18(diatom) shifts occurring today. This period of high delta O-18(diatom) values can be explained by the intensification of O-18-enriched Mediterranean precipitation events feeding the lake during the ice-free season. This agrees with other records from the southern Alps suggesting runoff intensification around 4200 cal BP. Possible changes in other climatic parameters may have played a concomitant role, including a decrease in the contribution of O-18-depleted Atlantic winter precipitation to the lake water due to snow deficit. Data recording the 4.2 ka BP event in the northwestern Mediterranean area are still sparse. In the Lake Petit watershed, the 4.2 ka BP event translated into a change in precipitation regime from 4400 to 3900 cal BP. This record contributes to the recent efforts to characterize and investigate the geographical extent of the 4.2 ka BP event in the Mediterranean area.
Plan de classementSciences du milieu [021] ; Géologie et formations superficielles [064] ; Ecologie, systèmes aquatiques [036] ; Sciences fondamentales / Techniques d'analyse et de recherche [020]
Descr. géo.FRANCE ; ALPES ; ZONE MEDITERRANEENNE
LocalisationFonds IRD [F B010075171]
Identifiant IRDfdi:010075171
Lien permanenthttp://www.documentation.ird.fr/hor/fdi:010075171

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