California margin

Leg 167 will investigate the evolution of oceanographic conditions in the north Pacific Ocean and will document changes in flow of the California Current system and associated changes in coastal upwelling. These data will be used to reconstruct north Pacific climate conditions through the Neogene, concentrating upon the time period since the advent of northern hemisphere glaciation, from -2.5 Ma to the present. Approximately one third of the proposed drill sites will also sample lower and middle Miocene sediments to reconstruct a Neogene history of the California Current. The results of Leg 167 drilling will also be used to understand better the links between climates of the north Pacific Ocean and western North America, particularly in terms of temperature change and changes in precipitation. Thirteen proposed sites and five alternates are organized into three transects across the California Current (Baja Transect, -30°N; Conception Transect, -35°N; and Gorda Transect, -40°N) and one coastal transect extending from northern Baja California to the California/Oregon border (30° to 42°N). Each of the three transects will compare deep-water sites near the core of the California Current to coastal upwelling sites near shore. The coastal transect will examine variations in upwelling and productivity along the California margin, and will also examine intermediate water properties in many of the basins of the California Continental Borderland. The proposed drill sites were chosen based upon two sites surveys (W9406 (R/V Wecoma) and EW9504 (R/V Ewing)). Much of the survey data (bathymetric swath maps, seismic profiles, and preliminary physical properties data from the sediment cores), for those sites that require it, can be obtained from the following WWW site: http://kihei.idbsu.edu/EW9504/camargin.html. SEG-Y versions of the seismic reflection data are also available from the National Geophysical Data Center (NGDC) where the digital data have been archived.