Geneza krzemieni górnego oksfordu w Krzemionkach Opatowskich

Early diagenetic concretionary flint nodules from the Upper Oxfordian oolitic and micritic limestones represent silicified crustacean burrows. Their occurence is confined to very shallow carbonate facies of barrier, lagoonal, and tidal flat origin. Fills of crustacean burrows commonly provided a nucleation centre for flint formation and thereby the template on which flint nodule beds were constructed. The reason for the special relationship between flint and crustacean burrows probably lie in the original texture (high permeability) of the burrow networks and also in the organic content (including the microbial assemblages) lowering the pH. Nodule horizons are developed more or less parallel to bedding, to form several widespread horizons of the regional correlative significance.