Map of the central and northern Oregon continental shelf and slope. Positions of seismic reflection datasets, seafloor samples, and exploratory wells used to produce the structure contour map of the late Miocene unconformity are shown. Farther seaward, the non-angular reflectors may represent a disconformity or a correlative conformity. The unconformity was found to be continuously traceable on much of the northern and central Oregon margin, with correlation to the north into Washington and south into southern Oregon more complex. The unconformity was digitized to produce an xyz file of unconformity position, with z initially in seconds two-way time, and later converted to depth using appropriate velocities from seismic refraction surveys and sonic logs.
Depths shown here are below current sea level.
The resulting xyz data were used to construct structure contours of the unconformity. Multichannel migrated seismic reflection profile on the central Oregon inner shelf, due west of Cape Foulweather. Thick sequences of basinal strata of Eocene to late Miocene age are seen below the unconformity and increasing thicknesses above the unconformity to the west. The unconformity is angular throughout much of the inner and middle shelf and is presumed to have been eroded subaerially. Multichannel migrated seismic reflection profile across the central Oregon shelf, west of Yaquina and Alsea Bays.