Strain localisation and incremental deformation within ice masses, Framnes Mountains, east Antarctica

Abstract

Mesoscale fracture analysis of brittle features has been used to identify zones of localised ductile deformation within an ice stream, moving at ~20 ma−1 in the Framnes Mountains, east Antarctica. Ground-based survey of three strain grids has been integrated with the detailed structural analysis to develop a model of temporal and spatial variation in strain localisation within large high strain zones. Modelled strain distributions are in good agreement with the occurrence and sense of movement across zones of high ductile strain which have been inferred from observed brittle features. The major zone of high strain is 3 km wide and 15 km long and deformed dextrally at a strain rate of 6.17 × 10−3 a−1 over the two year period of observation. Despite this constant annual strain rate the internal deformation was incremental, localised and temporal in nature resulting in the development of new zones of fracturing.