The interstitial water chemistry at ODP sites drilled along the southwest African margin is dominated by chemical processes involved in the degradation of organic matter and the dissolution and reprecipitation of carbonate phases. These processes are best considered as being related, with the alkalinity being generated by organic remineralization fueling carbonate diagenesis. In concert with a general north-to-south gradient of increasing sedimentary CaCO3 concentrations, therefore, variations in organic supply and preservation also intimately affect carbonate precipitation. In turn, carbonate diagenesis regulates distributions of dissolved Ca2+, Mg2+, and Sr2+, in addition to forming rigid dolomite layers and horizons in the sediment column. Analogously, PO43– released from organic matter during remineralization in the uppermost sediments serves as a source for the deeper precipitation of authigenic apatite phases. Downhole distributions of dissolved H4SiO4 appear to be influenced by diatom dissolution (source) and authigenic clay formation (sink). Finally, superimposed on these relatively long-term processes are perhaps diffusional signals of glacial-aged seawater variations in dissolved Cl–. These preliminary observations and hypotheses will be amplified upon and tested by postcruise research of a variety of dissolved constituents, including a suite of additional trace metal and isotopic measurements.