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Rapid deglaciation during the Bølling-Allerød Interstadial in the Central Pyrenees and associated glacial and periglacial landforms
- Source :
- Geomorphology, Geomorphology, Elsevier, 2021, 385, pp.107735. ⟨10.1016/j.geomorph.2021.107735⟩, Repositório Científico de Acesso Aberto de Portugal, Repositório Científico de Acesso Aberto de Portugal (RCAAP), instacron:RCAAP, Geomorphology, 2021, 385, pp.107735. ⟨10.1016/j.geomorph.2021.107735⟩, Dipòsit Digital de la UB, Universidad de Barcelona
- Publication Year :
- 2021
- Publisher :
- Elsevier BV, 2021.
-
Abstract
- International audience; The Central Pyrenees hosted a large ice cap during the Late Pleistocene. The cirques under relatively low-altitude peaks (2200–2800 m) include the greatest variety of glacial landforms (moraines, fossil debris-covered glaciers and rock glaciers), but their age and formation process are poorly known. Here, we focus on the headwaters of the Garonne River, namely on the low-altitude Bacivèr Cirque (highest peaks at ~2600 m), with widespread erosive and depositional glacial and periglacial landforms. We reconstruct the pattern of deglaciation from geomorphological observations and a 17-sample dataset of 10Be Cosmic-Ray Exposure (CRE) ages. Ice thickness in the Bacivèr Cirque must have reached ~200 m during the maximum ice extent of the last glacial cycle, when it flowed down towards the Garonne paleoglacier. However, by ~15 ka, during the Bølling-Allerød (B-A) Interstadial, the mouth of the cirque was deglaciated as the tributary glacier shrank and disconnected from the Garonne paleoglacier. Glacial retreat was rapid, and the whole cirque was likely to have been deglaciated in only a few centuries, while paraglacial processes accelerated, leading to the transformation of debris-free glaciers into debris-covered and rock glaciers in their final stages. Climate conditions prevailing at the transition between the B-A and the Younger Dryas (YD) favored glacial growth and the likely development of small moraines within the slopes of the cirque walls by ~12.9 ka, but the dating uncertainties make it impossible to state whether these moraines formed during the B-A or the YD. The melting of these glaciers favored paraglacial dynamics, which promoted the development of rock glaciers as well as debris-covered glaciers. These remained active throughout the Early Holocene until at least ~7 ka. Since then, the landscape of the Bacivèr Cirque has seen a period of relative stability. A similar chronological sequence of deglaciation has been also detected in other cirques of the Pyrenees below 3000 m. As in other mid-latitude mountain regions, the B-A triggered the complete deglaciation of the Garonne paleoglacier and promoted the development of the wide variety of glacial and periglacial landforms existing in the Bacivèr cirque.
- Subjects :
- 010504 meteorology & atmospheric sciences
Glacial landform
Rock glacier
010502 geochemistry & geophysics
01 natural sciences
Paraglacial
Cosmic-ray exposure dating
Deglaciation
Glacial period
Moraines
0105 earth and related environmental sciences
Earth-Surface Processes
Bølling-Allerød
Glacial landforms
geography
geography.geographical_feature_category
Glaceres
Pyrenees
Cirque
Glacier
Paraglacial processes
Geomorfologia glacial
15. Life on land
Pirineus
[SDU]Sciences of the Universe [physics]
Moraine
Physical geography
Glaciers
Central Pyrenees
Geology
Polished bedrock
Subjects
Details
- ISSN :
- 0169555X
- Volume :
- 385
- Database :
- OpenAIRE
- Journal :
- Geomorphology
- Accession number :
- edsair.doi.dedup.....bbe371663290a553daee56f7883895b0