Héritages glaciaires, périglaciaires et évolution récente : le cas du Nevado Coropuna (Andes centrales, sud du Pérou)

• Published in: Géomorphologie : relief, processus, environnement
• Main Authors: Forget, Marie-Emilie, Thouret, Jean-Claude, Kuentz, Adèle, Fontugne, Michel
• Format: Article in Journal/Newspaper
• Language: French
• Published: Groupe français de géomorphologie 2010
• Subjects: Andes centrales; calotte glaciaire; fluctuations climatiques; glacier rocheux; modelé glaciaire; Nevado Coropuna (Pérou); Central Andes; climatic fluctuations; glacial landform; ice cap; Nevado Coropuna (Peru); rock glacier; geo; hist; Ela; Ice; Ice cap; permafrost
• Online Access: http://journals.openedition.org/geomorphologie/6383

Tropical glaciers are very sensitive to climatic variations such as those induced by the El Nino Southern Oscillation (ENSO) in the central Andes. To better decipher the short-term climatic fluctuations that occurred in this region, it has been necessary to identify and date inherited glacial and periglacial landforms. This research is largely based on the analysis of the inherited landforms created by glacier ice fluctuations on the Nevado Coropuna massif and the ice cap (53.9 km2 in 2000) has been divided into eighteen glacier ice catchments. This study also resulted in a geomorphological map representing volcanic, glacial and periglacial landforms. This map and a combination of methods (geoarcheology, lichenometry, tephrostratigraphy and remote sensing) have allowed us to present a preliminary chronology of the recent ice and climatie fluctuations, compared to the available literature on southern Peru. We distinguish four periods, each of these including one to four stades. The present-day periglacial altitudinal zone (4500 – 5500 m) was probably frozen (i.e had a permafrost) during the Little Ice Age (LIA) but the absence of clear moraine landforms, which could be attributed to LIA, suggests that this period may have been characterized by stationary glacier ice fronts. Phases of colder and drier climate prior to the 19th century were rather favourable to the formation of rock glaciers in what is now the periglacial altitudinal zone. In addition to the study of rock glaciers, the use of the snow-line altitude (SLA) instead of the equilibrium line altitude (ELA) of the glaciers appears more adequate for assessing the short- to medium-term climate fluctuations, thus confirming SLA as a valid annual climatic indicator. Les glaciers tropicaux sont très sensibles aux variations climatiques et notamment à celles engendrées dans les Andes centrales par les phénomènes ENSO (El Niño Southern Oscillation). Afin de mieux saisir ces variations à court terme, il est nécessaire de déchiffrer les héritages glaciaires et ...