Post-Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10Be cosmic ray exposure dating

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

Abstract

Only a few chronological constraints on Lateglacial and Early Holocene glacier variability in the westernmost Alps have hitherto been obtained. In this paper, moraines of two palaeoglaciers in the southern Écrins massif were mapped. The chronology of the stabilization of selected moraines was established through the use of 10Be cosmic ray exposure (CRE) dating. The equilibrium line altitude (ELA) during moraine deposition was reconstructed assuming an accumulation area ratio (AAR) of 0.67. Ten pre-Little Ice Age (LIA) ice-marginal positions of the Rougnoux palaeoglacier were identified and seven of these have been dated. The 10Be CRE age of a boulder on the lowermost sampled moraine indicates that the landform may have been first formed during a period of stable glaciers at around 16.2±1.7 ka (kiloyears before AD 2017) or that the sampled boulder experienced pre-exposure to secondary cosmic radiation. The moraine was re-occupied or, alternatively, shaped somewhat before 12.2±0.6 ka when the ELA was lowered by 230 m relative to the LIA ELA. At least six periods of stable ice margins occurred thereafter when the ELA was 220–160 m lower than during the LIA. The innermost dated moraine stabilized at or before 10.9±0.7 ka. Three 10Be CRE ages from a moraine of the Prelles palaeoglacier indicate a period of stationary ice margins at or before 10.9±0.6 ka when the ELA was lowered by 160 m with respect to the end of the LIA. The presented 10Be CRE ages are in good agreement with those of moraines that have been attributed to the Egesen stadial. Assuming unchanged precipitation, summer temperature in the southern Écrins massif at ~12 ka must have been at least 2 °C lower relative to the LIA.

Detaljer

Författare
  • Felix Martin Hofmann
  • Helena Alexanderson
  • Philippe Schoeneich
  • Jordan R. Mertes
  • Laëtitia Léanni
  • Aster Team (Georges Aumaître, Didier L. Bourlès, Karim Keddadouche)
Enheter & grupper
Externa organisationer
  • Aix-Marseille University
  • Albert-Ludwigs University Freiburg
  • University Grenoble Alpes
  • Lund University
  • University Centre in Svalbard
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Geologi
Originalspråkengelska
TidskriftBoreas
StatusE-pub ahead of print - 2019 jun 17
PublikationskategoriForskning
Peer review utfördJa

Relaterad forskningsoutput

Hofmann, F. M., Helena Alexanderson, Schoeneich, P., Mertes, JR., Léanni, L. & ASTER Team, 2018, s. 25-25.

Forskningsoutput: KonferensbidragKonferensabstract

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