Summary of Results 1. Repeated vulcanicity is recognized in the Triassic of New Zealand. In Taringatura Survey District, Southland, andesite, dacite and rhyolite tuffs are present in large amount and at many horizons through a 28,000ft. section, inter-bedded with conglomerates, greywackes and indurated mudstones, mainly or entirely of marine deposition. 2. In the upper members of the Triassic succession fairly normal sedimentary diagenetic phenomena are observed, such as the formation of overgrowths on feldspars, cementation by quartz and chloritic minerals, and the replacement of volcanic glass by heulandite and analcime. These two types of zeolitization of tuffs are of regional importance in the Triassic of southern New Zealand. Heulauditization requires little chemical change except apparently a loss of soda, and in some cases a loss of silica, whereas analcimization, tinder the influence of saline waters, results in an increased soda content and decreased potash. A small proportion of the analcime crystallized in cross-cutting veinlets after consolidation. 3. In addition to connate waters trapped in the sediments, vast quantities of water were stored up in volcanic glass and in zeolites of early formation. As the temperature rose, perhaps to the order of 150–300° at the base of the pile, this stored-up water facilitated a special type of metamorphism, low-grade hydrothermal in its effect, although unrelated to igneous activity. 4. With increasing depth of burial, analcime gave way to quartz and feldspars, and in the lowest members it is represented only by pseudomorphs. At least a part of the interstitial authigenic albite of Upper Triassic sediments has formed directly from analcime. 5. With increasing depth also, a steadily increasing proportion of detrital plagioclase was albitized. This is not a simple metamorphic breakdown of lime-bearing plagioclase to albite and secondary lime-bearing minerals, although such a tendency was undoubtedly operative at the moderately elevated temperature at the base of the pile. In many cases the anorthite component was completely cleared from the crystal, apparently under the influence of soda released by the metamorphism of analcime, and the resulting pseudomorphs were purely albitic apart from sericite inclusions. 6. Albitized augite-andesite tuffs in the North Range have spilitic affinities. Their soda-rich nature may result from the early formation, and later destruction, of analcime. 7. In some cases the lime and alumina released during albitization crystallized within the same body of rock as laumontite, prehnite, pumpellyite, epidote, calcite, and sphene (by alteration of ilmenite). In other cases much of the lime was removed and concentrated elsewhere, especially in the altering beds of vitric tuff, where it was “fixed” as laumontite, which appears to replace earlier formed heulandite and even analcime. The albitized rocks also suffered a loss in potash. 8. Localized metasomatism occurred within a 450ft. bed of impure laumontitized tuff and resulted in the formation of quartz-albite-adularia-pumpellyite rocks, sometimes enriched in potash, sometimes in soda.