Geomorphological record of the glacial to periglacial transition from the Bølling–Allerød to the Holocene in the Central Pyrenees: the Lòcampo cirque in the regional context
Marcelo Fernandes, Marc Oliva, José María Fernández-Fernández, Gonçalo Vieira, David Palacios, Julia Garcia-Oteyza, Josep Ventura, Irene Schimmelpfennig, ASTER Team
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引用次数: 0
Abstract
In the highest tributaries of the Upper Garonne Basin, Central Pyrenees, cirques up to 2600 m a.s.l. were already deglaciated by 15–14 ka. The long-term deglaciation during Termination-1 (T-1) was interrupted by glacial advances within the cirques during the Bølling–Allerød (B-A) interstadial and the Younger Dryas stadial. The cirques preserve a variety of glacial and periglacial landforms whose chronologies are poorly known. This study is focused on the Lòcampo cirque (42°38′06″N and 0°59′10″E), Upper Garonne Basin, where a detailed geomorphological map and 10Be terrestrial cosmic ray exposure (CRE) dating allowed us to constrain the chrono-sequence between the glacial and periglacial domains. In the small Lòcampo cirque, a glacier formed a cirque moraine between 2200 and 2300 m a.s.l., which surrounds a relict rock glacier encompassing several transversal ridges. Additionally, longitudinal ridges typically observed in debris-covered glaciers are preserved between the moraine and the rock glacier. The eight-sample data set of CRE ages indicates the formation of the cirque moraine during the second half of the B-A, by 13.2±1.1 ka. Exposure ages from the rock glacier boulders show a range between 13.6±0.9 and 11.9±0.7 ka, which did not allow its formation to be chronologically constrained. Therefore, the environmental evolution following the moraine stabilization could follow the formation of a debris-covered glacier at the bottom of the Lòcampo cirque, with the subsequent formation of the rock glacier. After the rock glacier formation, its front rapidly ceased at 13.6±0.9 ka, while the upper ridges gradually stabilized until it became definitively relict at 11.9±0.7 ka or afterwards. These results show evidence of the complex glacial to periglacial transition that needs more robust chronological data sets to better understand the role of climate forcing and local topography during the deglaciation in mid-latitude mountain environments.
期刊介绍:
Boreas has been published since 1972. Articles of wide international interest from all branches of Quaternary research are published. Biological as well as non-biological aspects of the Quaternary environment, in both glaciated and non-glaciated areas, are dealt with: Climate, shore displacement, glacial features, landforms, sediments, organisms and their habitat, and stratigraphical and chronological relationships.
Anticipated international interest, at least within a continent or a considerable part of it, is a main criterion for the acceptance of papers. Besides articles, short items like discussion contributions and book reviews are published.