Growth and diagenesis of cryptalgal-bryozoan buildups within a Mid-Visean (Dinantian) cyclic sequence, Belgium

Cryptalgal-bryozoan carbonate buildups are reported from the Middle Visean (Upper Dinantian) near Namur, Belgium. They occur in a 20 m-thick, upward-shallowing, carbonate rhythm - the thickest in a succession of such rhythms.The rhythm comprises three phases; from bottom to top: (1) packstones-grainstones with rich and diverse biota, indicating open, shallow marine conditions; grading to (2) wackestones, with a poorer and more restricted biota, passing upwards to cryptalgal boundstones; and(3) mudstones with highly restricted and reduced biota.Small- to medium- sized mounds (2-11 m thick) occu... Mehr ...