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Geologic processes of accretion in the Cascadia subduction zone west of Washington State

January 1, 1999

The continental margin west of Oregon and Washington undergoes a northward transition in morphology, from a relatively narrow, steep slope west of Oregon to a broad, midslope terrace off Washington. Multichannel seismic (MCS) reflection data collected over the accretionary complex show that the morphologic transition is accompanied by significant change in accretionary style: West of Oregon the direction of thrust vergence in the wedge toe flip-flops between landward and seaward, whereas off Washington, thrust faults in the toe verge consistently landward, except near the mouth of the Columbia River where detachment folding of accreted sediment is evident. Furthermore, rocks under the broad midslope terrace west of Washington appear to be intruded by diapirs. The combination of detachment folding, diapirs, and landward-vergent thrust faults all suggest that nearly as far landward as the shelf break, coupling along the interplate decollement is, or has been, low, as suggested by other lines of evidence.

Citation Information

Publication Year 1999
Title Geologic processes of accretion in the Cascadia subduction zone west of Washington State
DOI 10.1016/S0264-3707(98)00001-5
Authors M. A. Fisher, E.R. Flueh, D. W. Scholl, T. Parsons, R. E. Wells, A. Tréhu, Uri S. ten Brink, C. S. Weaver
Publication Type Article
Publication Subtype Journal Article
Series Title Journal of Geodynamics
Series Number
Index ID 70021885
Record Source USGS Publications Warehouse
USGS Organization