Reconnaissance studies using DSDP cores have shown, however, that the Leg 167 drilling region is highly sensitive to climate change and that new ODP drilling would collect a detailed record of this variability. Significant contrasts in sedimentary environments occur along the California Margin, including the unique tectonic and sedimentary environments of the basins in the California Borderland. Site selection exploited these opportunities, constructing latitudinal, longitudinal, and depth transects. The oldest sediments from the inshore sites are Pleistocene in age, and from the offshore sites, middle or late Miocene. Coastal upwelling processes at the margin will be reflected in the nearshore sites, whereas nutrient supply by California Current processes will be reflected in the deeper sites.
All sites are within Sites also constitute two depth transects.
This transect takes advantage of the different sill depths within the California Borderlands for detailed study of the shallow intermediate water column. The oldest sediments from sites with the shallower water depths are at least late Pleistocene in age, whereas basal sediments from the sites with deeper water depths are typically late Miocene. These depth transects will provide sediments to investigate hypotheses about water-depth control of sedimentation processes and water column structure and its evolution through time.