Late Weichselian Ice sheet boundaries in North Western Russia: new insights from high resolution remote sensing and field observation

North Western Russia is a key area to study the growth, decay and interactions between Kara-, Barents-, and Scandinavian ice sheets during the Quaternary. Large scale mapping of the area has so far been hampered by the lack of high resolution topographic data. However, recent publication of digitized 1:100,000 topographic maps and merging with SRTM data enabled to create a 90 m DEM for the whole NW Russia. The significant increase in detail enabled us to identify previously unknown glacial features, especially frontal and lateral peri-glacial deposits. The large scale ice sheet limits are discussed in Fredin et al. (this meeting). In this presentation, we will focus on LGM landform structures and spillways in the Severnaya-Dvina areas.According to the new data, the Scandinavian ice-sheet boundary would have extended further south than previously modeled (Larsen et al., 2006, Boreas), which agrees with a previously described diamicton at Tolokonka section (Dvina valley). LGM ice-dammed lakes are thus reduced in volume compared to what was previously modeled. Sedimentary sequences from both Severnaya and Dvina valleys have been studied during the last decade and largely confirm our new model of LGM ice sheet extent in the area. Further investigations are being made to validate our hypothesis concerning ice dammed lakes extent and their thresholds. Based on the sampling of river-outcropped sections, we study the paleolacustrine archives and characterize sedimentation in terms of nature and processes. Characteristic rhythmites are observed and counted; thickness evolution of the couplets is also discussed as well as the spacial distribution of lacustrine facies. Preliminary results exhibit rapid processes with both laminated offshore sedimentation and proximal deltaic sandy deposits. Sedimentary evidences concerning potential lake level fluctuations are finally discussed.