Geometry of two glacial valleys in the northern Pyrenees estimated using gravity data

Stéphane Perrouty; Bérangé Moussirou; Joseph Martinod; Sylvain Bonvalot; Sébastien Carretier; Germinal Gabalda; Bernard Monod; Gérard Hérail; Vincent Regard; Dominique Remy

doi:10.1016/j.crte.2015.01.002

Geometry of two glacial valleys in the northern Pyrenees estimated using gravity data

Stéphane Perrouty ^{1, 2} Bérangé Moussirou ² Joseph Martinod ^{2, 3} Sylvain Bonvalot ² Sébastien Carretier ² Germinal Gabalda ² Bernard Monod ⁴ Gérard Hérail ² Vincent Regard ² Dominique Remy ²

1 UWO - University of Western Ontario

2 GET - Géosciences Environnement Toulouse

3 ISTerre - Institut des Sciences de la Terre

4 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

Abstract : We estimate using gravity data the thickness of post-glacial unconsolidated sediment filling two major glacial valleys in northern Pyrenees: the Gave de Pau valley between Pierrefitte-Nestalas and Lourdes, and the Garonne valley between Saint-Béat and Barbazan. One hundred and eighty-four new gravity data complete 74 measurements obtained from the International Gravimetric Bureau database. Negative residual anomalies resulting from the presence of small-density unconsolidated sediment approach 4 mgal in both the Gave de Pau and the Garonne valleys. Estimating the sediment thickness requires knowing the density contrast between Quaternary sediments and the underlying bedrock. Supposing this density contrast is 600 kg/m3, the maximum estimated thickness of post-glacial sediment is ∼ 230 and 300 meters, and the volume of sediment is 2.1 and 3.2 km3 in the Gave de Pau and Garonne valleys, respectively. In both valleys, the depth of Quaternary sediment suddenly increases at the confluence between two major glacial valleys (Gave de Pau – Gave de Cauterets, and Garonne – Pique confluences). Overdeepened basins are less deep downstream when approaching terminal moraines (Lourdes and Barbazan area), illustrating that the efficiency of glacial erosion depends on the ice flux flowing through valleys.

Keywords : Gravity Geomorphology Modeling Glacial valley Pyrenees

Type de document :

Article dans une revue

Comptes Rendus Géoscience, Elsevier Masson, 2015, 347 (1), pp.13-23. 〈10.1016/j.crte.2015.01.002〉

Domaine :

Planète et Univers [physics] / Sciences de la Terre

Liste complète des métadonnées

https://hal-brgm.archives-ouvertes.fr/hal-01357853
Contributeur : Anne-Marie Pouget <>
Soumis le : mardi 30 août 2016 - 15:15:50
Dernière modification le : mercredi 19 septembre 2018 - 01:37:41

Geometry of two glacial valleys in the northern Pyrenees estimated using gravity data

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