Landslide-dam paleolakes in the Central Pyrenees, Upper Gállego River Valley, NE Spain: timing and relationship with deglaciation

Abstract

The production of a cartographic landslide inventory in the glaciated headwaters of the upper Gállego River, Axial Zone of the Spanish Pyrenees, revealed several paleolakes. These relict lake basins are related to the blockage of drainages by postglacial earthflows and slides, mainly developed on Paleozoic slates. The paleolakes are recorded either by non-dissected infilled basins or by hanging and incised lacustrine terraces that persisted for thousands of years. The development of lakes upstream of landslides, was favored, despite their erodibility, by high-displacement rates and the occurrence of paired landslides on both sides of the valley. Radiocarbon and single-grain optically stimulated luminescence (OSL) ages obtained on the lake sediments range between 41.5 ± 3.9 ka and 15.1 ± 0.3 ka. These chronologies indicate prolonged landslide activity long after the early deglaciation in the upper Gállego River Valley. The landslide-lake dating results support the interpretation that the regional maximum ice extent (MIE) in the Pyrenees occurred during the marine isotope stage 4 (MIS 4), long before the global Last Glacial Maximum (LGM).