FIRST DIGITAL GEOLOGICAL MAP DATASET OF MARIE BYRD LAND: A PRODUCT OF THE SCAR GEOMAP PROJECT

Due to the presence of extensive sheet, bedrock exposures in Marie Byrd Land (MBL) are relatively sparse. However, they provide important constraints on the geological evolution and glacial history of West Antarctica. The most extensive area of outcrops is found in the Ford Ranges and Edward VII Peninsula, bordering the Ross Ice Shelf. We used ground-based geological observations to develop the first digital geological map for Marie Byrd Land, as a component of the new SCAR GeoMap project (http://www.scar.org /geomap). Feature attribution uses the international GeoSciML data format. The map covers a coastal area of 135 000 km² between 140°E to 160°E, from 75°S to 80°S, at around 1:250 000 scale. Exposed rock is delimited by 911 polygons, occupying 250 km² that comprises 0.2% of the total area. There are 119 mapped till deposit polygons (11.2 km²), 58 supraglacial tills (5.7 km²) and 69 seasonal water features (21.5 km²) that provide a baseline for past and future glaciological change. Rendered in Esri© ArcMap, the GIS will be made publicly available as an ArcGIS map service and Google Earth files.

Using the new GIS, an interpretive map of sub-glacial bedrock geology has been generated for the region, drawing upon archival airborne geophysical data (magnetics, gravity, ice thickness, and sub-ice topography) recorded at 5.3 and 10.6 km line spacing over the Ford Ranges (Luyendyk et al., 2003), augmented by marine bathymetry (e.g. Luyendyk et al., 2001; Sorlien et al., 2006). Polygon features correspond to geological formations, and line features to inferred crustal faults at regional scale. Pliocene and younger volcanism, and glacial deposits were mapped with extreme care due to their potential consequences for ice sheet stability. The current configuration is rendered upon BEDMAP2 subglacial topography. The re-examination of archival data is timely within ongoing geophysical exploration and dataset compilation for Antarctica, such as SCAR ADMAP, NASA Icebridge, and POLEnet. The new subglacial framework of bedrock structure in MBL is used to test existing hypotheses about the tectonic evolution and identify factors that may affect ice sheet stability. It provides a geological context for the eastern boundary of the Ross Ice Shelf region being mapped by the 2015-2018 USAP ROSETTA-Ice airborne geophysical investigation.