UNLOCKING OF THE HINES CREEK AND ASSOCIATED FAULTS, EASTERN ALASKA RANGE, ALASKA: EVIDENCE FOR CENOZOIC DISPLACEMENT

Geologic mapping of the Hines Creek fault and the adjacent Trident Glacier and McGinnis Glacier transcurrent faults to the north in the Eastern Alaska Range, Alaska reveals that these faults were active during the Cenozoic. Previously, the Hines Creek fault, which is considered to be part of the Denali strike-slip fault system, was interpreted to have been welded shut during the intrusion of the Late Cretaceous Buchanan Creek pluton in the northeast Healy quadrangle. Geologic mapping along the Hines Creek fault in the northeast Healy quadrangle and northwest Mount Hayes quadrangle reveals that: (1) the Buchanan Creek pluton is truncated by the Hines Creek fault; and (2) a tectonic collage of fault-bounded slices of various granitic plutons, metagabbro, meta basalt, and sedimentary rock of the Pingston terrane occurs south of the Hines Creek fault splay.

The Trident Glacier and McGinnis Glacier faults comprise two, but less-extensive faults that occur 1 to 5 km north of the Hines Creek fault and extend for about 60 km laterally in the northwest Mt. Hayes quadrangle. Geologic mapping along these faults reveals that the older bedrock of the mid- to late-Paleozoic Yukon-Tanana terrane is: (1) juxtaposed against late Pleistocene glacial moraines along thrust or strike-slip fault planes; and (2) juxtaposed against Oligocene-to-Pliocene sedimentary rocks along thrust or strike-slip fault planes. To the southeast, the Trident Glacier and McGinnis Glacier faults merge with the Hines Creek fault that in turn merges with the main strand of the Denali strike-slip fault in the area of the Delta River and Canwell Glacier.

Field relations for the Hines Creek and adjacent transcurrent faults to the north indicate the following: (1) the faults are major parts of the Alaska Range suture zone; (2) the faults have been active throughout most of the Cenozoic; and (3) the faults have exhibited young (Pleistocene) movement.