3D MAPPING OF SHEAR ZONES AND MELT FLOW NETWORKS IN THE FOSDICK MOUNTAINS GNEISS DOME OF WEST ANTARCTICA, USING SATELLITE IMAGERY UPON A HIGH RESOLUTION DEM

The Fosdick Mountains gneiss dome, an exposure of middle to deep crust exhumed during development of the West Antarctic rift system, contains four generations of Cretaceous anatectic granite that are distinguishable on the basis of U Pb zircon age, Hf and O isotopes in zircon, and field relationships. Near-vertical exposures of the north margin of the recently deglaciated range show continuous and discontinuous granite networks that are vestiges of pathways of former melt (e.g. McFadden et al. 2010, doi:10.1029/2009TC002492) that contributed to the flow of crust within the back arc region of the Cretaceous Phoenix-Gondwana plate boundary. To advance our understanding of flow trajectories and the lateral continuity of structures that promoted or inhibited melt movement as a mechanism of crustal flow, we use DigitalGlobe WV-2 satellite imagery draped upon a digital elevation model computed from a stereographic pair of high resolution panchromatic images (sequential scenes acquired 45 s apart). DEMs were computed using ERDAS Imagine™ LPS eATE, refined by MATLAB-based interpolation scripts to remove artifacts in the terrain model according to procedures developed by the Polar Geospatial Center at U. Minnesota. Global Mapper™ was used to render in 3D the imagery draped upon the DEMs. The 0.5 m resolution Worldview scenes provide access to upper cliff elevations and rock exposures that could not be reached due to glacier hazards or remote location. Rock unit identification relies upon ground truth established from previous work in 2005-2011 or prior, augmented by spectral analysis of the 8-band imagery using ESRI ArcGIS™ 10.1. A primary aim of the ongoing research is the creation of a 3D geological map that offers the means to examine the geometrical and geospatial relationships between high strain zones, nappe-scale folds, and sequential granite phases produced from differing sources, in order to understand patterns of crustal scale flow induced by a change in plate boundary conditions along the Cretaceous active margin of Gondwana. The 3D perspective views reveal structural and geological features that are not apparent from ground observation, DEM nor satellite imagery alone. The methods that we employ are broadly applicable for 3D bedrock mapping in other remote or inaccessible localities that lack vegetation cover.