Glacier fluctuations during the Late Glacial and Holocene on the Ariège valley, northern slope of the Pyrenees and reconstructed climatic conditions

Vincent Jomelli (1) , Emmanuel Chapron (2) , Vincent Favier (3) , V.R. Rinterknecht (1, 4) , Regis Braucher (4) , Nicolas Tournier (2) , Simon Gascoin (5) , Renaud Marti (6) , Didier Galop (2) , Stéphane Binet (7, 8) , César Deschamps-Berger (5) , Hélène Tissoux (9, 10) , Georges Aumaitre (4) , Didier Bourlès (4) , Karim Keddadouche (4)

1 LGP - Laboratoire de géographie physique : Environnements Quaternaires et Actuels
2 GEODE - Géographie de l'environnement
3 IGE - Institut des Géosciences de l’Environnement
4 CEREGE - Centre européen de recherche et d'enseignement des géosciences de l'environnement
5 CESBIO - Centre d'études spatiales de la biosphère
6 Maison de la Télédétection
7 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
8 Biogéosystèmes Continentaux - UMR7327
9 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
10 HNHP - Histoire naturelle de l'Homme préhistorique

The glacier evolution from two valleys located near Vicdessos, French Pyrenees, is deciphered from 17 in situ cosmic ray exposure (CRE) dating. In the Picot valley, Late Glacial glacier advances were documented during Heinrich Stadial 1 (HS1), while a rock glacier developed or was reactivated during the mid-Holocene. In the upper Médécourbe valley, the largest visible ice extent occurred during the Younger Dryas (YD) or earlier. At least two moraines formed during the early Holocene were dated, while an undated moraine located close to the head of the catchment may have been formed either during the Late Holocene or the Little Ice Age. A mass balance model suggests that a temperature about 5.1 °C cooler than today, without precipitation change, would be necessary to form a moraine at the base of the Picot catchment during HS1 at 2000 m a.s.l. A temperature about 3.9 °C cooler than today is necessary to explain a moraine formed during the Late Glacial–YD transition at Médécourbe at 2200 m. Comparing CRE dating from Picot and Médécourbe with those in the Pyrenees and the Alps highlights original glacial patterns. In the Picot catchment whose summit is below the current regional ELA, the absence of YD and Late Holocene moraines is consistent with the general low-altitude deglaciation trend documented in the northern and southern slope of the Pyrenees, but differs from high-altitude Pyrenean and Alpine records. However, due to specific geomorphological conditions, the glacial evolution of the Médécourbe valley took place differently compared to other low-altitude catchments in the Pyrenees.

Domaines: Planète et Univers [physics]; Interfaces continentales, environnement

Vincent Jomelli, Emmanuel Chapron, Vincent Favier, V.R. Rinterknecht, Regis Braucher, et al.. Glacier fluctuations during the Late Glacial and Holocene on the Ariège valley, northern slope of the Pyrenees and reconstructed climatic conditions. Mediterranean Geoscience Reviews, 2020, 2 (1), pp.37-51. ⟨10.1007/s42990-020-00018-5⟩. ⟨insu-02476511⟩