Dolomite and dedolomitization in Danian bryozoan limestone from Fakse, Denmark

Abstract

The carbonate rock complex of Fakse Quarry includes small intraformational bodies of dolomite that occur in three different ways: 1) completely dolomitized bryozoan limestones; 2) partially dolomitized bryozoan limestones in which the larger skeletons have resisted total dolomitization, and 3) concretionary dolomite. Scattered secondary rhombohedral porosity is observed in bryozoan limestones indicating former occurrences of dolomite. The carbon isotopes suggest that dolomitization took place in a zone of methanogenesis, an early diagenetic event. Dedolomitization is most pronounced in the dolomite concretions and to a lesser extent in the dolomitized bryozoan limestone beds. Dedolomitization appears to be governed by the access of meteoric water along cleavage traces spreading to the entire dolomite crystals. -from Authors