PII] S91532696"87#999904 Geologic processes of accretion in the Cascadia subduction zone west of Washington State

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 o} Washington [ Mul! tichannel seismic "MCS # re~ection data collected over the accretionary complex show that the morphologic transition is accompanied by signi_cant change in accretionary style] West of Oregon the direction of thrust vergence in the wedge toe ~ip!~ops between landward and seaward \ whereas o} 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 [ 0887 Elsevier Science Ltd [ All rights reserved[