Geochemistry of sediments at DSDP Sites 579, 580, and 581

The elemental composition of sediments from Sites 579 (38°38'N, 153°50'E) and 580 (41°37'N, 153°59'E) is dominated by contributions from terrigenous detritus (including numerous thin ash beds) and opal-rich biogenic debris, with the terrigenous component increasing in dominance in the youngest sediments as the flux of Pleistocene eolian debris associated with Northern Hemisphere glaciation has increased. Diagenesis related to redox-sensitive reactions in near-surface sediments has had a marked impact on the distributions of Mn and S. At Site 581 (43°56'N, 159°48'E), the reduced biosiliceous clays corresponding to the sections at Sites 579 and 580 are underlain by a normal oxidized North Pacific "red clay" sequence.

As at other North Pacific sites, the concentrations of Mn and Fe (as oxyhydroxides), Ba (as barite), and P (as fish debris) vary inversely with the accumulation rates of the clays. The cherts underlying the clays at Site 581 are noteworthy for their high P contents (comparable to values for biosiliceous clays) and high Fe and Mn relative to Ti and Al, suggestive of derivation from well-oxidized pelagic sediments.