Analyses of 82 samples collected from the surface of the continental shelf between the Oregon-California border and Eureka, Calif., indicate that the background gold content on this shelf is about 0.1 ppb (part per billion). Four anomalous tracts, which range in extent from 10 to 30 square kilometers, have gold values above 10 ppb, and the richest sample contains 300 ppb. The anomalous areas seem to lack a close correlation with water depth, but they are related to areas underlain by soft Cenozoic strata that contain small quantities of dispersed gold originally derived from lodes in the Klarnath Mountains. This relationship suggests that the offshore gold accumulations are lag concentrates produced from the Cenozoic deposits by wave erosion during the postglacial rise in sea level. Gold contents at the surface are too low for economic recovery, and drilling will be required to determine whether the anomalous areas are underlain by higher grade material.
Additional publication details
USGS Numbered Series
Gold distribution on the sea floor off the Klamath Mountains, California