Résumé
The Nussloch loess sequences were sampled at close intervals (10
cm) and documented in respect of their stratigraphy, palaeopedology, sedimentology, palynology, malacology and geochemistry, and were dated using radiocarbon and OSL methods. For each stratigraphic unit, the results of both the field studies and the analytical and geochronological data obtained cast light upon the response of the loessic environment to global climatic variations during the last cycle. The basal soil complex underwent a pedosedimentary evolution similar to those of the bordering area (complex Luvisol/Greyzem/ “steppe soil”) which reflects the classic progression towards increased continentality of the environment between the end of the Eemian (5d) and the beginning of the full glacial stage (Pleniglacial). The Lower Pleniglacial corresponds to an initially very arid phase dominated by the accumulation of loess, followed by the deposition of stratified niveo-eolian sands. The Middle Pleniglacial complex (ca. 55–30) is clearly characterised by the inhibited loessic sedimentation. It is primarily marked by two phases of stabilisation recorded in the form of weathered horizons (Cambisols) which are separated by a rather thin layer corresponding to loessic sedimentation with tundra gleys. This intermediate phase brings together organic silt deposits which record an interstadial dated at 32–33
ka
14C BP. The thick loessic accumulations of the Upper Pleniglacial (>10
m), which clearly began to accumulate before the oxygen isotope stage (OIS) 3/2 boundary, show evidence of vulnerability to considerable fluctuations in response to variations in wind dynamics and the intensity of deflation in the Rhine valley. Finally, a proposed correlation of loess–palaeosol stratigraphies from Germany, Belgium and France, spanning the entire last interglacial–glacial cycle, is presented.