The California margin is marked by strong coastal upwelling and consequent development of intense oxygen-minimum zone (OMZ). The strength and width of OMZ is controlled not only by intensity of upwelling but by concentration of dissolved O2 and lateral advection of intermediate water. At present, upwelling is most intense between 33° and 44°N, the position and intensity of which is sensitive to the pattern of atmospheric circulation over the California margin. A significantly different situation almost certainly prevailed during the last glacial episode (Lyle et al., 1992). At present, warm, nutrient-rich, and O2-poor intermediate water (California Undercurrent) from the south continues as far north as Vancouver Island (~50°N) with the northernmost extent of this influence controlled by the position of the West Wind Drift (Hickey, 1979). But probable influence of North Pacific Intermediate Water (NPIW) at the depth of OMZ today is also suggested, and possible intensification of NPIW during the last glacial episode is widely discussed (van Green et al., 1996; Lund and Mix, 1998; Gardner et al., 1997; Keigwin, 1998). Thus, changes in both atmospheric circulation pattern and source and intensity of intermediate waters should have strong influence on the OMZ.
In their studies of Santa
Barbara Basin during the last glacial episode, Kennett and Ingram (1995) and
Behl and Kennett (1996) recognized changes of bottom-water oxygenation level in
association with millennial-scale climatic cycles known as Dansgaard-Oeschger
cycles (e.g., Dansgaard et al., 1993). They attributed these changes to
switching of the intermediate-water sources between the south and the north. If
true, this is a good evidence that the intermediate-water circulation cell,
independent of the deep-water conveyor belt driven by North Atlantic Deep Water,
was intensified and expanded in North Pacific during stadials of the last
glacial episode (Gonopolski et al., 1998). This further suggests that such
waxing and waning of NPIW occurred in association with Dansgaard-Oeschger
cycles. However, it has not yet been confirmed whether bottom-water conditions
of Santa Barbara Basin faithfully reflect those of the intermediate water
flowing along the California margin. To test this hypothesis, we planned a
cooperative high-resolution multiparameter study at Ocean Drilling Program (ODP)
Site 1017 located on the upper slope facing to open northeastern Pacific near
the entrance of Santa Barbara Basin. This paper reports a part of the result
from this cooperative study. Parameters examined in associated papers include 
18O
and 13C
of planktonic and benthic foraminifers, 13C
and 15N
of organic matter, redox-sensitive minor elements, and biomarkers (Kennett et
al., Chap. 21, this
volume; Irino and Pedersen, Chap.
23, this volume; Ishiwatari et al., Chap.
24, this volume; Behl et al., Chap.
22, this volume; Ostertag-Henning and Stax, Chap. 26, this volume). The
synthesis of these results will be presented elsewhere.
In this study, we aim to test the possibility of the changes in flow direction and intensity of the intermediate waters through examination of detrital provenance and sedimentary structures in conjunction with detrital grain size, respectively.
