Figure 2 - uploaded by Brigitte Van Vliet-Lanoë
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Structures de déformation syn-sédimentaire de la coupe de Cestas. A. Vue générale de la coupe avec subdivision des principaux intervalles sédimentaires. B. Structure de liquéfaction dans le plan de stratification. C. Figure de charge pédiculée (silt) évoluant vers un pseudo-nodule. D. Pseudo-nodule silteux pédiculé. E. Pseudo-nodule silteux. F. Pseudo-nodule silteux à pédoncule diffus. Remarquer la perturbation du litage associée à l'écoulement per descensum de la masse silteuse. G. Filon clastique (flèche). H. Pseudo-nodule et microfailles syn-sédimentaires (flèche).
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... Comparable conditions certainly prevailed during earlier glacial cycles, also characterized by roughly similar climatic deterioration events (Masson-Delmotte et al., 2010). Although the historic seismicity of the study region remains low, a coseismic origin for some features cannot be ruled out as suggested by Schneider et al. (2012) for Larrousey (Plate IV). Since the origin of these deformations remains a matter of debate, they will not be used here for the purpose of palaeoenvironmental reconstruction. ...
... Comparable conditions certainly prevailed during earlier glacial cycles, also characterized by roughly similar climatic deterioration events (Masson-Delmotte et al., 2010). Although the historic seismicity of the study region remains low, a coseismic origin for some features cannot be ruled out as suggested by Schneider et al. (2012) for Larrousey (Plate IV). Since the origin of these deformations remains a matter of debate, they will not be used here for the purpose of palaeoenvironmental reconstruction. ...
Detailed stratigraphic analysis and numerical dating (OSL, IRSL, ESR, 14C) of Pleistocene coversands in southwest France enable the construction of a renewed chronostratigraphic framework for sand depo-sition. The chronological data obtained from sandsheet units testify to the development of transgressive dunefields since at least the Middle Pleistocene (MIS 10). Three main phases of accumulation occurred during the Last Glacial. The oldest one (64e42 ka) is associated with wet sandsheet facies, histic horizons and zibar-type dune fields, which reflect deposition in a context strongly influenced by the groundwater table. The Late Pleniglacial (24e14 ka) corresponds to the main phase of coversand extension in a drier context. Silty gley horizons suggest, however, local interruptions of sand drifting during GS 2.1. Late-glacial stabilization of the coversands may not have occurred before GI-1c (Allerød), which was typified by the development of cumulic arenosols. These were covered by parabolic dunes during the Younger Dryas. The variations in extent of the emerged continental shelf during the glacialeinterglacial cycles may explain the uneven geographical distribution of sand deposition through time. Because of coastline retreat up to 100 km north of 45 N during the LGM lowstand, the coversands were unable to reach the northern part of the basin. Comparison with other European regions highlights stronger affinities of the French record with Portugal than with the Netherlands and Great Britain, probably because of reduced influence of permafrost.
