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TitleThe Skipjack Island Fault Zone: a geohazard and benthic habitat-forming structure separating the San Juan Islands, Washington State, USA from British Columbia, Canada
AuthorTodd, B J; Barrie, J V; Greene, H G
SourceGEOHAB 2016 - Marine Geological and Biological Habitat Mapping: marine environment mapping and interpretation - from the coast to the deep ocean, abstract booklet; 2016 p. 58
Year2016
Alt SeriesEarth Sciences Sector, Contribution Series 20160010
PublisherGeoHab
MeetingGEOHAB 2016 - Marine Geological and Biological Habitat Mapping; Winchester; GB; 2-6 May 2016
Documentbook
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia; Western offshore region
NTS92B; 92G/01; 92G/02; 92G/03; 92G/04; 92G/05; 92G/06; 92G/07; 92G/08
AreaVancouver Island; Washington State; San Juan Islands; Canada; United States
Lat/Long WENS-124.0000 -122.0000 49.5000 48.0000
Subjectsmarine geology; tectonics; structural geology; surficial geology/geomorphology; Nature and Environment; geophysics; plate tectonics; plate margins; crustal movements; deformation; bedrock geology; structural features; fault zones; faults; faults, thrust; fold structures; marine organisms; benthos; geophysical surveys; seismic surveys, marine; seismic reflection surveys; seismic profiles, marine; marine sediments; marine sediment cores; photography; Skipjack Island Fault Zone; Devil's Mountain Fault Zone; geological hazards; marine biology; habitats; rockfish
ProgramMarine Geohazards, Public Safety Geoscience
AbstractThe Skipjack Island Fault Zone has been mapped in the San Juan Islands between Vancouver Island, Canada, and the Washington State mainland, USA. A decade ago, interpretation of multibeam sonar seafloor imagery revealed that Skipjack Island, an east-west striking sedimentary bedrock outcrop, was a fault-controlled structural feature. A major fault separates Skipjack Island from a deformed sedimentary bedrock outcrop on the seafloor to the north.
Recently the Skipjack Island Fault Zone's morphology and extent has been explored both to the west and east of the island using seismic reflection profiling, sediment coring, and seabed photography that is supported, in part, by the Non-Governmental Organization (NGO) Research Now. The character of the Skipjack Island Fault Zone is well defined locally by the interpreted seismic profiles, which show active faults that displace recently deposited sediments. The central part of the fault zone, near Skipjack Island, appears as a near-vertical structure that has been subjected to left-lateral motion; the evidence is bedrock exposure on the seabed north of the island where folded strata bend eastward against the fault, the result of drag from the fault motion. This structure has produced ideal habitat for various rockfish species that are endangered or listed. Interpretation of recent geophysical data suggests an extension of the Skipjack Island Fault Zone further to the east where it either cuts through or transitions into a thrust fault and fold belt. A blind thrust fault is tentatively identified north of Lummi Island, another area where rockfish inhabit the seafloor.
The Skipjack Island Fault Zone is interpreted to be the northern boundary of the San Juan Archipelago with the Devil's Mountain Fault Zone being the southern boundary. Both of these faults represent the longest continuous fault zones of the San Juan Archipelago and are generally oriented east-west and are actively deforming the seafloor. This deformation is continuing to alter and produce benthic habitats for rockfish.
Summary(Plain Language Summary, not published)
The Skipjack Island Fault Zone has been mapped in the San Juan Islands. Data show active faults that displace recently deposited sediments. The central part of the fault zone, near Skipjack Island, appears as a near-vertical structure that has been subjected to left-lateral motion; the evidence is bedrock exposure on the seabed north of the island where folded strata bend eastward against the fault, the result of drag from the fault motion. Interpretation of recent geophysical data suggests an extension of the Skipjack Island Fault Zone further to the east where it either cuts through or transitions into a thrust fault and fold belt. The Skipjack Island Fault Zone is interpreted to be the northern boundary of the San Juan Archipelago with the Devil's Mountain Fault Zone being the southern boundary. Both of these faults represent the longest continuous fault zones of the San Juan Archipelago and are generally oriented east¿west and are actively deforming the seafloor.
GEOSCAN ID297906