Ice‐flow patterns and dispersal of erratics at the southwestern margin of the last Scandinavian Ice Sheet: signature of palaeo‐ice streams

Abstract

Richardt, N. 2003 (March): Ice-flow patterns and dispersal of erratics at the southwestern margin of the last Scandinavian Ice Sheet: signature of palaeo-ice streams. Boreas, Vol. 32, An extensive set of proxy-data was acquired from eastern and central Denmark in order to study the dynamic behaviour of the southwestern margin of the last Scandinavian Ice Sheet. We examine the last three glacier advances of the Late Weichselian: the Main advance from central Sweden, representing the maximum ice extent at this time (c. 21-20 ka BP), and the two succeeding Baltic advances (c. 18-15 ka BP). Directional properties from tills and glaciotectonic overprints are used to reveal large-scale flowline patterns. Together with the geomorphological outline of ice margins, flowlines were successively more fan-shaped, indicating that the dependence of the subglacial topography increases as ice advances become younger. It is suggested that while the ice thickness decreases, more lobate configurations of ice margins are created as a result. Clast-compositional data derived from the fine-gravel fraction in tills are used to reconstruct dispersal patterns of erratic material. The dispersal patterns during the three advances show a gradually diminishing influence of local Pre-Quaternary bedrocks and older glacial deposits, and progressively longer transport distances of far-travelled erratics. We speculate that the principal factor governing this development is a successively decreasing interaction between the ice and its bed, which influences the concentration of erratics, debris comminution processes and the basal ice velocity. We envisage the Main advance from central Sweden as a slow-flowing inter-stream ice body with high bed interaction compared to the succeeding Baltic advances, which we regard to have been rapid flowing ice streams with limited bed interaction.

Subglacial methanogenesis: A potential climatic amplifier?

“…[21] Our argument rests on the observation that subglacial tills in North America and Europe consist predominantly of local material, transported over just tens of kilometers [Shilts, 1984;Clark, 1987;Kjaer et al, 2003]. To quantify this effect, we use Boulton's [1984] model of till generation for a flow line running from the ice divide to the margin of the European ice sheet.…”

Unravelling the complex nature of the Upper Weichselian till section at Gdynia Babie Doły, northern Poland

“…This is due to the fact that in the area north and northwest of Babie Doły Quaternary deposits are isolated from the Cretaceous and Paleogene substrate by soft and/ or fine-grained Miocene and Pliocene sediments (Leszczyński, 2012). The Quaternary sediments, including the older glacial deposits, might have furnished additional protection, as documented by several authors (e.g., Kjaer et al, 2003;Czubla, 2006;Czubla et al, 2010Czubla et al, , 2013. In our view, the content of Neogene rocks in the fine gravel fraction (5-10 mm) of the upper subunit is negligible for other reasons.…”

Reconstructing flow paths of the Middle Pleistocene British Ice Sheet in central-eastern England: the application of regional soil geochemical data

“…However, the relative strength of the spatial geochemical trends within the dataset was unexpected. Kjaer et al (2003), for example, argued that the far-travelled lithological component of tills increases with height within a till profile -a function of reduced interaction of basal ice with local lithologies as substrate is progressively buried by till. Whilst we are not presenting vertical profile data within this study, the degraded and undulating surface of both till sheets should, following this theory, leave a more spatially variable and weaker geochemical trend reflecting different levels of outcropping till.…”