Classical theory of the genesis of Natargids (solonetz) involves the upward movement of sodium from a water table. Examination of 24 pedons representing four Soil Series developed in glacial till on the Northern Great Plains (Montana) suggests that Natrargids (solonetz and solodized‐solonetz) and Haplargids (soloth) can develop in the absence of a water table. The four soils occur as a complex on “panspot” rangeland with the soloth and solodized‐solonetz on microknolls and the solonetz in microdepressions. The panspot soils have significantly (p = 0.01) greater B horizon clay contents than associated non‐panspot soils. X‐ray diffraction analyses indicate decomposition of smectite inherited from the parent material in the sola of all soils. Solonization of the panspots is driven by reduced infiltration and subsurface water movement in response to matric and osmotic potential gradients. Panspots occur over high points in the till‐shale boundary where the wetting front penetrates into the salty, calcareous till. Movement of sodium upwards from the shale contact results in dispersion of the panspot B horizon. Natric horizon development causes reduced infiltration and subsurface interpedon translocation of water, salts, and amorphous materials.

During Leg 66, a transect was drilled across the Middle America Trench off Mexico. In this report, interstitial water analyses for Sites 487 (on oceanic crust), 490, 491, and 492 (continental slope apron), and 493 (upper continental slope) are presented. All sites are characterized by high sedimentation rates, and as a result sulfate reduction and methane generation processes are very important. At Sites 490 through 492 decreases in chlorinity are evidence of the presence of gas hydrates. At Site 493 a sharp increase in dissolved calcium and the complete depletion of dissolved magnesium just above basement indicate that weathering of continental crust is still an ongoing process.

Interstitial water studies from sites drilled during a transect of the Walvis Ridge indicate that concentration increases in calcium and decreases in magnesium toward and into the basement. These trends can be understood principally in terms of reactions taking place in Layer 2 of the oceanic crust. At Site 525, however, some removal of magnesium occurs within the sediment column. Concentration maxima of dissolved strontium clearly indicate that carbonate recrystallization occurs throughout the carbonate sediments, and studies of the Sr/Ca ratio in carbonates indicate that in chalks and limestones recrystallization is essentially complete. Predictions of dissolved strontium maxima generally fail; this can be understood as removal of strontium in basal sediments and/or basalts.

Interstitial water profiles obtained at Sites 530 and 532 of DSDP Leg 75 indicate complex concentration depth profiles resulting from diagenetic reactions taking place in the sediments. At both sites, large depletions in dissolved sulfate, resulting from bacterial sulfate reduction reactions, are accompanied by increased alkalinity values and also by increased dissolved ammonia concentrations. At Site 530, high sedimentation rates in the upper 200 m of the sediment column have led to a minimum in dissolved sulfate. Deep-seated reactions in basal sediments and/or basalts at this site cause downhole increases in dissolved calcium and decreases in dissolved magnesium. At Site 532, phosphate liberated by sulfate reduction has led to reaction with calcium ions to form authigenic Ca-phosphate minerals.