MINERALS/Glauconites 547 temperature decrease, whereas all other factors for glauconitization remained favourable Indeed, the presence of the appropriate bacteria (which may be temperature-controlled) for organic matter degradation and iron reduction, plus faecal pellets (which are most abundant on the continental shelf in water 20 C; hence it is only known from the tropics Verdine preferentially forms where the water depth is 20–60 m (but