17. Iron-rich Sediments Cored during Leg 8 of the Deep Sea Drilling Project

A sequence of amorphous iron r>xide-rich sediments, interbedded with iron-free calcareous nannoplankton oozes, occurs in the basal zones of Sites 74 and 75 of the Deep Sea Drilling Project, immediately overlying basalt. These sediments have affinities with iron and manganeserich sediments previously described from the crest of the East Pacific Rise. It is considered most likely that this sediment association forms a basal iron and manganeserich facies over much of the central east Pacific Basin and that it was formed by precipitation from bottom waters which were enriched in metals by submarine hydrothermal exhalations associated with volcanism.