Deep-burial diagenesis of the siliciclastic Ordovician Natal Group, South Africa

摘要: Abstract The siliciclastic Ordovician Natal Group, distributed along the east coast of South Africa, is a predominantly fluvial sequence deposited by braided streams. Although strata are not metamorphosed, they have been strongly affected deep burial diagenesis that left many diagenetic textures and structures. Well-preserved pressure solution pits overcompaction fractures on pebbles cobbles found in conglomeratic units near base succession, whereas convex–concave sutured grain-contacts, fractured arenaceous grains, deformed detrital mica, concertina-shaped muscovite, deep-burial albite calcite cements ubiquitous higher sequence. In addition, pressure-shadows stylolites, illitization clay minerals, recrystallization quartz cement also common. These structures demonstrate Group had environment. Thickness data overlying fluid-inclusion temperatures show depths for probably ranged between 4800 7200 m. This conclusion supported high crystallinity indices illite taken from succession.