Surficial geology interpretive map from the inner continental shelf off the northern Oregon and southern Washington coast based on sidescan-sonar imagery and sediment samples

Two 21-day field operations were conducted in 1997 and 1998 in the estuaries and on the inner continental shelf off the northern Oregon and southern Washington coast. These cruises aboard the R/V Corliss were run in order to generate reconnaissance maps of the seafloor geology and the shallow subsurface stratigraphy using sidescan-sonar and seismic-reflection mapping techniques. The 1998 cruise also collected sediment grab samples, bottom photographs, and video images to verify the sidescan-sonar imagery and to document the seafloor geology. The combination of these data with previously collected sediment sample data (Robert, 1974; Nittrouer, 1978; and Smith et. al., 1980) has been used to define the extent and lithology of shelf sediments associated with the Columbia River littoral cell. This work is one component of a larger project studying the erosion of the Washington Oregon coasts and is being coordinated by the U.S. Geological Survey and the Washington State Department of Ecology. The reasons for collecting these data are to provide a regional synthesis of the offshore geology for this project and to support a wide variety of management decisions and to provide a basis for further process-oriented investigations.