Early diagenesis in rapidly accumulating sediments on the Alboran slope, ODP site 976

The oxidation and reduction that occur during early diagenesis of sediments has been studied in the interstitial waters of a rapidly accumulating sedi mentary sequence from the Mediterranean margin of Spain. A series of reacti ons that are mediated by progressively lower free energy derived from oxida tion of organic matter is evident in the sedimentary sequence. Iron and man ganese are rapidly reduced. Phosphate and alkalinity maxima at a subbottom depth of 15 m indicate maximal organic matter degradation. Methane first ap pears at similar to 20 m subbottom after sulfate is depleted, and its conce ntrations quickly climb.