(Table 1) Interstitial water chemistry at DSDP Leg 81 Holes

Interstitial water studies on samples obtained during Leg 81 have revealed substantial changes with depth in dissolved calcium, magnesium, strontium, potassium, and lithium. Calcium and magnesium concentration changes result from alteration reactions, primarily in the basalts and also in the volcanic sediments overlying the basalts. Similarly, depletions in potassium are the result of reactions in volcanic sections of the drill holes. Lithium has its main source in the volcanic sediments. On the other hand, strontium-concentration maxima occur at the ooze-chalk boundary and are the result of carbonate recrystallization reactions. Distinct correlations between calcium gradients and extents of concentration maxima in strontium with sedimentation rates suggest (1) build up of calcium concentrations below diffusion communication depth and (2) increased rates of recrystallization of carbonate with rate of sedimentation. The latter process is probably related to the more "corrosive" character of the sediments as the result of organic carbon diagenesis.