CONCLUSIONS

We analyzed the minor and trace element contents in a suite of 197 samples corresponding to the last 25 k.y. to examine with high resolution the provenance and upstream transport paths of sediments deposited at ODP Site 1017, as well as to define selected diagenetic enrichments. The following observations can be made:

1. Re, U, Mo, and As are diagenetically enriched within sediments, which implies perennial oxygen depletion at 1 km depth on the south-central California margin for at least the last 25 k.y.
2. The depth profiles of these elements imply that higher export production from the middle to early MIS 1 fostered severe O₂ depletion in near-interface pore waters. The relative independence of the C_org and Mo profiles on the millennial scale during MIS 2 suggests that intermediate-water hydrography was more important than the vertical settling flux of C_org in controlling the relative oxygen deficit.
3. Sr variations are largely controlled by the input of biogenic carbonate.
4. Q-mode factor analysis of a minor element assemblage associated with terrigenous detritus suggests that compositional variations are the result of a textural control (variable mixtures of sand- and silt-sized detritus) and a provenance control (variable inputs of mafic and felsic finer grained detritus).
5. Temporal variations in composition indicate that the contribution of the mafic end-member was higher during MIS 2 than during MIS 1. This can best be explained as the result of enhanced delivery to Site 1017 during MIS 2 of detritus derived from north-central California.