We could not obtain interstitial water samples at Sites 1100, 1102, and 1103 along the shelf transect because of the lithified nature of most material recovered, except for one sample from 2.95 mbsf in Hole 1100C (Table T3). The interstitial water chemistry of this diatom-bearing silty clay shows evidence of bacterial degradation of organic matter and silica dissolution comparable to that observed in the uppermost few meters of sediment at Sites 1095, 1096, and 1101 on the continental rise. The sulfate concentration (29 µM) does not differ significantly from seawater, so active sulfate reduction must occur at greater depths. The high concentration of manganese (29 µM), however, reflects dissolution of Mn oxides under suboxic conditions. Slightly increased alkalinity (3.56 mM), ammonium (77 µM), and phosphate (9.5 µM) relative to seawater also reflect moderate amounts of organic-matter decay. Dissolved fluoride (62 µM) has decreased slightly from its seawater concentration and suggests fluoride uptake by the sediment, whereas the high dissolved silica concentration (0.57 mM) indicates that biogenic opal begins dissolving above 3 mbsf. All other dissolved constituents (e.g., calcium, magnesium, potassium, and strontium) have concentrations similar to seawater and thus show no signs of either organic or inorganic diagenesis.