Analysis of the diagenetic and metamorphic history of the Devonian limestones shows them to be a predominantly bioclastic series ranging from calcilutites to coarse biomicrites and biosparites in composition. Six main microfacies are recognized. Low-grade metamorphism has been responsible for the introduction of new fabrics, but has not completely obliterated the effects of diagenesis. The degree of recrystallization depended on the stress environment of the rock. The limestones are interpreted as clastic accumulations of skeletal material, rather than reef formations. They probably developed within areas of prolific growth of carbonate-secreting organisms that at no time formed a growth lattice with a topographic expression resembling that of modern reefs.