| Title | The Skipjack Island fault zone - an active transcurrent structure within the upper plate of the Cascadia Subduction Complex |
| |
| Author | Greene, H G; Barrie, V; Todd, B J |
| Source | Geological Society of America, Abstracts With Programs vol. 49, no. 6, 241-5, 2017 p. 1, https://doi.org/10.1130/abs/2017AM-297426 |
| Image |  |
| Year | 2017 |
| Alt Series | Natural Resources Canada, Contribution Series 20170293 |
| Publisher | Geological Society of America |
| Meeting | Geological Society of America Annual Meeting 2017; Seattle, WA; US; October 22-25, 2017 |
| Document | Web site |
| Lang. | English |
| Media | on-line; digital |
| File format | html; pdf |
| Province | British Columbia; Western offshore region |
| NTS | 92B; 92G/01; 92G/02; 92G/03; 92G/04; 92G/05; 92G/06; 92G/07; 92G/08 |
| Area | Vancouver Island; Victoria; Vancouver; Fraser River Delta; Washington State; San Juan Archipelago; Orcas Island; Bellingham; Canada; United States of America |
| Lat/Long WENS | -124.0000 -122.0000 49.5000 48.0000 |
| Subjects | marine geology; tectonics; structural geology; surficial geology/geomorphology; geophysics; plate margins; plate motions; bedrock geology; structural features; faults, transcurrent; faults, thrust; fold
structures; structural analyses; tectonic evolution; deformation; marine sediments; displacement; geophysical surveys; seismic surveys, marine; seismic reflection surveys; seismic profiles; Cascadia Subduction Zone; Skipjack Island Fault Zone;
Devil's Mountain Fault Zone; Cascadia Forearc; Sierra Nevada Terrane; Phanerozoic; Cenozoic; Quaternary |
| Program | Public Safety
Geoscience Marine Geohazards |
| Released | 2017 10 01 |
| Abstract | The 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 and sediment coring. The character of the Skipjack Island fault zone is well defined locally
by the interpreted seismic profiles, which show active faults that displace sediments deposited since the Last Glacial Maximum. The central part of the fault zone, near Skipjack Island, appears as a near-vertical structure that has been subjected to
left-lateral motion as evidenced by a bedrock exposure on the seabed north of the island where folded strata bend eastward against the fault, the result of drag from 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 fault zones represent the longest continuous faults of the San Juan Archipelago, are generally oriented east-west, and are actively deforming the seafloor and producing a clockwise
rotation of the major islands within the Archipelago. The Skipjack Island fault zone may represent the northern boundary of the Cascadia forearc where the northward propagating Sierra Nevada tectonostratigraphic terrane is impinging upon stable North
America. |
| Summary | (Plain Language Summary, not published)
The Skipjack Island fault zone was mapped in the San Juan Islands between Vancouver Island, Canada, and the Washington State mainland, USA. The fault
zone¿s morphology and extent has been explored using geophysical and geological tools. The character of the Skipjack Island fault zone is indicated by active faults that displace sediments deposited since the last glacial period. 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 fault zones represent the longest continuous faults of the San Juan Archipelago, are
generally oriented east¿west, and are actively deforming the seafloor and producing a clockwise rotation of the major islands within the Archipelago. |
| GEOSCAN ID | 306309 |
|
|