Small Scale Folding in NEEM Ice Core

• Main Author: Westhoff, Julien
• Format: Thesis
• Language: unknown
• Published: 2014
• Subjects: Greenland; Tilting; ice core
• Online Access: https://epic.awi.de/id/eprint/36396/; https://epic.awi.de/id/eprint/36396/1/BA-Westhoff.pdf; https://hdl.handle.net/10013/epic.44229; https://hdl.handle.net/10013/epic.44229.d001

NEEM is a drilling site in north western Greenland, from which a 2500 m long ice core has been derived. The ice has been analyzed with visual stratigraphy to make layering visible. This thesis analyzes the layering from top to bottom in terms of folding events. Small disturbances of layers start to appear around 1560 m depth and folding is visible at 1750 m depth from the surface. Below 2160 m there has been so much deformation that a qualitive description is not possible. From 1750 m to 2160 m there is an evolution of folding, where normal folds, then Z-folds and shear zones, and in greater depths many Z-folds in one layer appear. They are a result of increasing strain rate, leading to deformation, which in this depth is mainly ductile. Fold types with a brittle component are also visible in form of detachment folds. The dominant structures are Z-folds located at shear zones which were created by deformation, resulting in these diagonal shear zone in the core. These shear zones have also been analyzed with the fabric analyzer to find the main c-axis orientation within these zones. The main orientation is caused by a tilting of the grains during deformation and another part due to recrystalization processes. The orientation of these shear zones can be estimated by using the linescanner images which show the ice in different focus depths in the horizontal level of the core and reveal a general orientation to the top left of the images, caused by shear stress from the right in a small angle.