The Quaternary and Neogene paleoceanography of the California margin is poorly understood, primarily because the marine sedimentary record is poorly sampled for sediments older than about 50 ka. Typically, the high sedimentation rates along the margin limit the recovery to <130 ka for even the longest piston cores from standard oceanographic vessels. For this reason, the highest priority objective on Leg 167 was the collection of continuous high-resolution sediment records from the initiation of Northern Hemisphere glaciation (2.6 Ma) to the present. We also needed to collect more slowly deposited sediments from the seaward sites of the onshore-offshore transects for a longer Neogene perspective. These drill sites (Fig. 1; Sites 1010, 1016, and 1021) formed the anchors for the development of a new biostratigraphic framework tied to the paleomagnetic chronology (Cande and Kent, 1992, 1995). They have also given us major insight into oceanographic conditions along the California margin since the latest middle Miocene.
It has been hypothesized from the Santa Barbara Basin drilling (Site 893; Kennett and Ingram, 1995) that major changes have occurred in the upper intermediate waters along the southern California margin. In particular, they suggested that a more oxygenated source of intermediate waters appeared in glacial intervals, perhaps from the North Pacific. Sites 1011-1014 were drilled in the California Borderlands, and Site 1017 was drilled off Point Conception to better study the evolution of Pacific intermediate waters through the Pleistocene. The California Borderlands basins have sill depths that range from about 1500 to 450 m. The bottom waters of each basin are samples of discrete intermediate waters taken from the sill depth into that basin (Fig. 6). Ultimately the data from the different drill sites can be combined to study a water-column depth transect through much of the Pleistocene.
Along the central and northern California margin there is a general lack of long paleoceanographic records, and a high priority was to collect both intermediate- and deep-water records where submillennial paleoceanographic events could be documented. For this reason, we drilled Sites 1019 (980 m), 1018 (2476 m), and 1020 (3038 m), all of which have high average sedimentation rates (Table 1).
Because high-resolution continuous records were a priority, all sites were triple cored with the advanced piston core (APC), and a continuous splice of the sediment section was assembled aboard the JOIDES Resolution (Lyle, Koizumi, Richter, et al., 1997). The continuous records are being used for high-resolution sedimentological and paleoceanographic studies. Table 1 is a synopsis of the results of Leg 167 drilling. It contains the locations of the Leg 167 drill sites and pertinent information about the length and age of continuous sediment records. For the most part, the continuity is based upon shipboard correlations, but the ages incorporate new stratigraphic information generated since the cruise has ended (Fornaciari, Chap. 1, this volume; Kennett et al., Chap. 2, this volume; Maruyama, Chap. 3, this volume; Barron, Chap. 4, this volume; Hayashida et al., 1999). Because the California margin typically has high deposition of organic matter, we were also interested in diagenesis within the sediment column. We designed our sampling of interstitial waters to be of higher resolution than the average ODP sampling in the upper sediment column (one whole round per core for the first six cores followed by every third core thereafter; see "Explanatory Notes" chapter in Lyle, Koizumi, Richter, et al., 1997). Some sites had higher sampling (Site 1010 for oxygen isotope analysis, and Site 1019 to study gas hydrates).