| Summary: | A Ground Penetrating Radar (GPR) survey was conducted in April of 2008, collecting 27 km of radar profiles in Sandflugtdalen, a permafrosted glacio-fluvial bedrock valley in West Greenland. Due to low electric permittivity of frozen soil, GPR has good depth penetration of permafrost, up to 80 m using low-frequency (50 MHz) antennae. Resolution and visibility of reflections from subsurface structures are improved by gain application and frequency filtering. Migration reconstructs the radar image to make it look closer to the geological structure in the subsurface. Using the principles of radar stratigraphy, 5 types of radar facies are identified in the dataset - chaotic, chaotic with numerous hyperbolic reflections, parallel, oblique and reflection-free; the facies are interpreted respectively as glacial till, push moraine, stratified deposits in (fan) delta bottomsets or lake deposits, lacustrine delta foresets and bedrock. Average bedrock depth in Sandflugtdalen is 50 meters. Bedrock barriers, overlaid by push moraines, divide Sandflugtdalen in 3 subbasins. Radar packages of delta foresets, till and lacustrine deposits in each subbasin are interpreted to be genetically related, having been deposited in moraine-dammed lakes, that formed during progressive stages of glacial retreat, between 10.5 and 5 ka ago. A 3-D model of the bedrock surface is generated and based on the model the sediment volume in the mapped area is estimated as 0.37 km^3. Modeling the bedrock and mapping the sedimentary architecture in a filled glacial valley generates a base-case for model validation of short-term climate changes and effects on glacier and sedimentary system. Applied Geophysics and Petrophysics Geoscience & Engineering Civil Engineering and Geosciences
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