(Table 1) Depth and revised depth from ODP Sites 169-1033 and 169-1034

The Holocene section in Saanich Inlet, Vancouver Island, British Columbia, is 50-70 m thick. Cores from Saanich Inlet obtained during Leg 169S of the Ocean Drilling Program afford an excellent opportunity to obtain an ultrahigh-resolution paleomagnetic and environmental magnetic record for the Holocene and Late Pleistocene of western Canada. We have used an automated, long-core cryogenic magnetometer to study over 380 m of continuous u-channel samples from ODP Sites 1033 and 1034, the two sites that constitute Leg 169S. Holocene records of paleomagnetic inclination and intensity show excellent intra-site correlation and can be used to fine-tune the lithologic correlation among cores from each site. The Late Pleistocene magnetic records provide a means of intra-site correlation of the otherwise featureless marine clay. Near the Holocene/Late Pleistocene boundary, both sites contain a magnetic intensity feature that is interpreted as a Missoula-type flood event on the Fraser River. The composite Holocene inclination records from the two sites are quite similar and provide a means of comparing current age-models that are based on radiocarbon dating of material from each site. This comparison shows only minor differences in the available age-models. It also provides strong evidence that the sediments of Saanich Inlet represent a reliable record of geomagnetic field behavior.

Granulometry, mineralogy and geochemistry of sediments from ODP Hole 169-1037B and Site 169-1038

Central Hill is in the northern part of the Escanaba Trough, which is a sediment-filled rift of southern Gorda Ridge. Central Hill is oriented north-south and is associated with extensive sulfide deposits. Hydrothermal alteration of sediment from Site 1038 was studied through analyses of mineralogy and the chemistry and oxygen isotopic compositions of one nearly pure clay sample. In addition, Site 1037 was drilled to establish the character of the unaltered sedimentary sequence away from the hydrothermal centers of the Northern Escanaba Trough Study Area (NESCA). Mineralogy of the clay-size fraction of turbiditic and hemipelagic sediments of Hole 1037B are predominantly quartz, feldspar, pyroxene, illite, chlorite, and smectite, representing continental-derived material. Cores from Hole 1038I, located within the area of Central Hill but away from known active vent areas, recovered minor amounts of chlorite/smectite mixed-layer clay in the fine fraction, indicating a low-temperature hydrothermal alteration. The 137.4-m-thick sediment section of Hole 1038G is located in an area of low-temperature venting. The uppermost sample is classified as chlorite/smectite mixed layer, which is underlain by chlorite as the dominant mineral. The lowermost deposits of Hole 1038G are also characterized by chlorite/smectite mixed-layer clay. In comparison to Hole 1038I, the mineralogic sequence of Hole 1038G reflects increased chloritization. Intensely altered sediment is almost completely replaced by hydrothermal chlorite in subsurface sediments of Hole 1038H. Alteration to chlorite is characterized by depletion in Na, K, Ti, Ca, Sr, Cs, and Tl and enrichment in Ba. Further, Eu depletion reflects a high-temperature plagioclase alteration. A chlorite 18O value of 2.6 indicates formation at a temperature of ~190°C. It is concluded that the authigenic chlorite in Hole 1038H formed by an active high-temperature fluid flow in the shallow subsurface.