HEMATITE BIOCONSTRUCTIONS IN THE DEVONIAN GRIOTTES (CENTRAL PYRENEES)

Two Famennian red ''griottes'' limestones of the Central Pyrenees have hematite bioconstructions in the matrices and cavities. They range fr om simple coatings to columnar complex microstromatolites. Similar bio constructions are known in the Frasnian red mud-mounds of Belgium and in a Carboniferous ''griotte'' of Asturias. A microbial origin for the hematite is therefore plausible acid is responsible for the pigmentat ion of these red carbonates.