GEOLOGIC AND GEOMORPHIC CHARACTERIZATION OF FROZEN DEBRIS LOBE CATCHMENTS ALONG THE DALTON HIGHWAY, SOUTHERN BROOKS RANGE, ALASKA

Frozen debris lobes (debris mass-movement features on permafrost slopes) are present along the Dalton Highway corridor in the southern Brooks Range, Alaska. Active downslope movement of these features presents potential hazards and geologic-engineering challenges to the highway as well as the adjacent Trans Alaska Pipeline System. To better characterize frozen debris lobes and assess their associated geologic hazards, we initiated a focused study along a 20-mile stretch of the Dalton Highway between Wiseman and Chandalar Shelf. Here we present observations of the bedrock geology and geomorphology of eight frozen debris lobe catchments, based on ArcGIS analysis of multi-date remotely sensed imagery and 2013 summer field work.

Preliminary results indicate that frozen debris lobes form in gullies, cored by less-competent material such as phyllite, slate, and chloritic schist and flanked by ridges of competent bedrock such as limestone, marble, metasandstone, and gneiss. Catchment areas are characterized by solifluction lobes, fractures, slumps, channels, standing water, permafrost, and minimal vegetative cover. Debris is contributed to the frozen debris lobes by a variety of slope processes, including solifluction, rockfall, slope failure, and runoff. Characterizing the geologic attributes of the overall catchment area is an important component to understanding the hazard potential of the frozen debris lobes. Our observations and results will provide new information useful for maintenance of current infrastructure and planning for future development in the corridor.