Active and potentially active faults in or near the Alaska Highway corridor, Dot Lake to Tetlin Junction, Alaska
Description
In 2005, the Alaska Division of Geological & Geophysical Surveys initiated a multi-year geologic field study focused on a corridor centered along the Alaska Highway between Delta Junction and the Canada border. The purpose of this project is to provide geologic information relevant to a proposed Alaska-Canada natural gas pipeline and other future development in the corridor. The scope of this project includes identification of active faults and characterization of seismic hazards. During the 2008 field season the active fault studies were focused on the central part of the corridor between Dot Lake and Tetlin Junction. Field studies included helicopter and fixed-wing air reconnaissance augmented by interpretation of stereo air photos, remotely sensed images, ground reconnaissance, and field mapping. Detailed investigations were conducted where the reconnaissance identified lineaments indicative of Holocene surface faulting. In addition, detailed field studies were conducted of several lineaments identified in the published literature as possible active faults. The detailed studies included field mapping, topographic profiling, trenching, and 14C dating of surficial sediments associated with lineaments exhibiting characteristics of active faults. Two faults and a large fault-related anticline were found to have generated late Pleistocene and Holocene surface deformation in the Dot Lake-Tetlin Junction section of the corridor. These structures, the eastern part of the Dot "T" Johnson fault, the Cathedral Rapids fault, and the Giant Moletrack anticline, are active structures in the eastern part of the NFFTB. Detailed investigation of the Mansfield and Dennison Fork lineaments, identified as candidate active faults in the literature, produced conclusive evidence that they are not active faults. Detailed study of a third suspect lineament, the Bear Creek lineament, was inconclusive.