SCIENTIFIC OBJECTIVES AND METHODOLOGY
Summary of Primary Objectives
- To understand how a major eastern boundary current system and associated
upwelling centers respond to growth of northern-hemisphere glaciers (all
- To assess feedbacks between continental and oceanic climates in the
north Pacific and North America (all sites).
- To obtain depth transects suitable to study variations in north Pacific deep
water properties and carbonate deposition (North Site CA1-1033 m; Site CA2-1951 m; Site CA3-2731 m; Site CA4-3075 m; Site CA6-3316 m; Site CA5-4242 m. South Site CA15-1182 m; Site CAM2-2047 m; Site CA8-2508 m; Site CA14-3495 m; Site CA11-3873 m).
- To understand variations in the production, preservation, and burial of organic carbon in a well-studied, highly productive continental margin setting (all sites).
- To sample gas hydrates (Site CA1).
Summary of Secondary Objectives
- To study tectonic development of the active continental margin of western North America (all sites).
- To investigate the deformation of the Gorda Plate (Sites CA3 and CA4).
- To test the response of continental margin sedimentation to Cordilleran uplift (all sites).
- The acquisition of Franciscan and Gorda Plate basement where possible without compromising primary sedimentary objectives (Sites CA2, CA3, CA4, CA5, CA6, CA11, CA14, and CAM2 ).
The tectonic objectives, although of secondary importance, are also necessary for paleoceanographic reconstruction, because many of the sites have moved hundreds of kilometers with respect to North America during the Neogene. The continental basement underneath Site CA-2, for example, is now located just south of the Mendocino triple junction but may have been separated from the rest of North America as far south as northern Baja California (Bohannon and Parsons, 1995).
Highest priority on Leg 167 will be given to the sampling of upper Neogene sediments (Pliocene and younger), but five of the proposed drill sites will sample middle and lower Miocene sediments. The older sedimentary sections will be instrumental to understanding the Neogene paleoceanographic evolution of the north Pacific climate.
To 167 Drilling Strategy
167 Table of Contents