Did Pyrenean glaciers dance to the beat of global climatic events? Evidence from the Würmian sequence stratigraphy of an ice-dammed palaeolake depocentre in Andorra

Abstract

The ice-marginal depositional sequence of La Massana provides a chronostratigraphic benchmark for reconstructing the Würmian glacial evolution of the Valira catchment in Andorra, SE Pyrenees. The sedimentary record of Andorra confirms the asynchronous chronology of glacier fluctuations in different parts of the Pyrenean mountain range. A major ice recession occurred at the end of Marine Isotope Stage (MIS) 4. High magnitude valley-glacier fluctuations during MIS 3 constitute another important finding. Major readvances occurred toward the end of MIS 3, whereas MIS 2 (in particular, the global Last Glacial Maximum, or LGM) featured sharp contrasts in ice recession rates between Pyrenean valleys. Substantial distances separated MIS 4 glacier fronts (the Würmian maximum ice extent, or MIE) from those reached during the global LGM, in contrast to situations in the eastern Pyrenees, where Würmian MIE and global LGM ice fronts nearly coincided. Overall, the Valira glaciers reveal patterns that are more similar to those recorded elsewhere in the western and central Pyrenees than in the eastern Pyrenees. The rapid fluctuations recorded by Andorran glaciers during the second half of the Würm also suggest a response to global forcing events such as Heinrich events in the North Atlantic.

Timing of deglaciation and rock glacier origin in the southeastern Pyrenees: a review and new data

“…; Turu et al . ). These ages are contemporaneous with those obtained from Optically Stimulated Luminescence (OSL) techniques in the southern Central Pyrenees, where MIE fluvioglacial deposits have been dated to around 68–64 ka (Lewis et al .…”

Quaternary glaciation in the Mediterranean mountains: a new synthesis

“…The timing of glaciations in the Mediterranean mountains has been constrained using a range of approaches. Examples presented in this volume include cosmogenic nuclide exposure dating of boulders and bedrock surfaces (Akçar et al 2015;Federici et al 2016;Palacios et al 2016;Pope et al 2015;Turu et al 2016), radiocarbon dating of basal glacial lake deposits (Giraudi & Giaccio 2015;Serrano et al 2016;Turu et al 2016), Ar/Ar dating of tephras in mountain basins (Giraudi & Giaccio 2015), optically stimulated luminescence dating of glacio-fluvial outwash deposits (Serrano et al 2016;Turu et al 2016) and uranium series dating of secondary carbonate cements Serrano et al 2016) in glacial and glacio-fluvial deposits.…”

“…This interval was characterized by glacier advances or phases of glacier stability across central and northern Europe, but it has, until now, rarely been documented in the Mediterranean mountains. Turu et al (2016) set out detailed evidence from an ice-marginal palaeolake sediment record in Andorra for a much larger marine isotope stage (MIS) 4 advance compared with that of MIS 2. Comparison with other areas of the Pyrenees highlights the asynchronous records of glacier fluctuations in different parts of these mountains and raises important questions about the underlying causes.…”

Long-term entrenchment and consequences for present flood hazard in the Garona River (Val d'Aran, Central Pyrenees, Spain)

“…A time lag between the maximum ice extent in the Pyrenees (> 40 ka) recorded during MIS 4, and the global Last Glacial Maximum (LGM) culminating ca. 21 ka during MIS 2 (Mardones and Jalut, 1983;Montserrat-Martí, 1992;Bordonau, 1992;García-Ruiz et al, 2003;Calvet et al, 2011;Delmas, 2015;Turu et al, 2016) has been proved for the Pyrenean glaciers. In the Garona valley, the glaciolacustrine and till deposits at the base of the Barbazan Lake fill sequence, about 30 km downstream of Les, have yielded an age of 31.16 ± 1.7 ka BP (32.037 to 39.407 ka cal BP), showing the presence of a glacier on that site until 26.6 ± 0.46 ka BP (29.786 to 31.446 ka cal BP) (Andrieu et al, 1988;Jalut et al, 1992).…”