Insights into subglacial processes inferred from the micromorphological analyses of complex diamicton stratigraphy near Illmensee‐Lichtenegg,Höchsten,Germany |
| |
| Authors: | JOHN MENZIES DIETRICH ELLWANGER |
| |
| Institution: | 1. Department of Earth Sciences, Brock University, St Catharines, Ontario, Canada L2S 3A1;2. Landesamt für Geologie, Rohstoffe und Bergbau Baden‐Württemberg, Albertstrasse 5, D‐79104 Freiburg im Breisgau, Baden‐Württemberg, Germany |
| |
| Abstract: | Menzies, J. & Ellwanger, D. 2010: Insights into subglacial processes inferred from the micromorphological analyses of complex diamicton stratigraphy near Illmensee‐Lichtenegg, Höchsten, Germany. Boreas, 10.1111/j.1502‐3885.2010.00194.x. ISSN 0300‐9483. Investigations of a 30‐m‐high section of Pleistocene sediments at Illmensee‐Lichtenegg, Höchsten in Baden‐Württemberg provide detailed information on subglacial conditions beneath the Rhine Glacier outlet of the Alpine ice sheet in southern Germany. The sediment exposure extends from an upper cemented sand and gravel (Deckenschotter) into diamictic units that extend down to weathered Molasse bedrock. The exposure reveals sediments symptomatic of active syndepositional stress/strain processes ongoing beneath the ice sheet. Macrosedimentology reveals diamicton subfacies units and a strong uni‐direction of ice motion based on clast fabric analyses. At the microscale level, thin‐section analyses provide a substantially clearer picture of the dynamics of subglacial sediment deformation and till emplacement. Evidence based on detailed micromorphological analyses reveals microstructural strain and depositional markers that indicate a subglacial environment of ongoing soft bed deformation in which the diamictons can be readily identified as subglacial tills. Within this subglacial environment, distinct changes in pore‐water pressure and sediment rheology can be detected. These changes reveal fluctuating conditions of progressive, non‐pervasive deformation associated with rapid changes in effective stress and shear strain leading to till emplacement. This site, through the application of micromorphology, increases our understanding of localized subglacial conditions and till formation. |
| |
| Keywords: | |
|
|
