High mountain deglaciation. Glacial morphology, evolution and morphogenetic phases in the Posets massif (Aragonese Pyrenees)

Abstract

The Posets massif is the second highest massif in the Pyrenees (3.368 m). It is a deglaciated high mountain massif, that includes three small glaciers at the highest cirque of Posets peak. The deglaciation evolution and the transition from a glacial environment to a periglacial one have been established from (1) geomorphological mapping, (2) depositional landforms description and (3) paleoELA reconstruction. Five main morphogenetic phases are defined: Phase I, Pleniglacial, during this phase the massif is covered by ice and glaciers which fed the Ésera and Cinqueta valley glaciers; Phase II, Inner advance maximum, main advance of glaciers in the massif, of Late Glacial age; Phase III, Inner retreat, also Late Glacial age; Holocene deglaciation, backward motion of glaciers phase and periglacial features; Phase IV, Smaller advance, glacial historic period, the Litle Ice Age (L.I.A.); and Recent retreat. The L.I.A. morphogenetic evolution is formed by six main phases. Nowadays, the Posets massif is a high rocky mountain, very recently deglaciated, with a marginal glacial morphodynamic and an intense cryonival activity.