ABSTRACT: Geology along the Fairweather-Queen Charlotte Fault System off Southeast Alaska and British Columbia from GLORIA Images and Seismic-Reflection Data

Terry R. Bruns, Paul R. Carlson, Andrew J. Stevenson, Maxwell R. Dobson

GLORIA images collected in 1989 along southeast Alaska and British Columbia strikingly show the active trace of the Fairweather-Queen Charlotte transform fault system beneath the outer shelf and slope; seismic-reflection data are used to track the fault system across the continental shelf where GLORIA data are not available.

From Cross Sound to Chatham Strait, the fault system is comprised of two sets of subparallel fault traces separated by 3 to 6 km. The fault system crosses the shelf from Icy Point to south of Yakobi Valley, then follows the shelf edge to Chatham Strait. Between Chatham Strait and Dixon Entrance, a single, sharply defined active fault trace underlies the upper and middle slope. This fault segment is bounded on the seaward side by a high, midslope ridge and by lower slope Quaternary(?) anticlines up to 35 km wide. Southeast of Dixon Entrance, the active fault trace trends back onto the outer shelf until midway along the Queen Charlotte Islands, then cuts back to and stays at midslope to the Tuzo Wilson Knolls south of the Queen Charlotte Islands. The fault steps westward at Tuzo Wilson nolls, which are likely part of a spreading ridge segment.

Major deep-sea fans along southeast Alaska show a southeastward age progression from older to younger and record both point source deposition at Chatham Strait and Dixon Entrance and subsequent (Quaternary?) offset along the fault system. Subsidence of ocean plate now adjacent to the Chatham Strait-Dixon Entrance fault segment initiated development of both Mukluk and Horizon Channels.

AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990