Two examples of carbonate-beachrock formation have been studied in Tunisia and on the Bahamas. lt appears evident that cementation takes place under a cover of sediment where the carbonate grains are immobilized and where primary cements are precipitated in a marine or fresh-water, phreatic or vadose environment close to the water table. Oblique beach stratification and keystone vugs (typical for the swash zone) are thus preserved. Coastal erosion exposes this preferentially cemented layer, and marine cementation in the intertidal zone further indurates the rock. Wave action often washes away the underlying non-consolidated sediment. This causes the beachrock to break into blocks which (by gravity) may glide into the subtidal zone. Except for secondary marine vadose cements , all cements types found in beachrocks also occur in other environments. The identification of ancient beachrocks should therefore not be based on cementation criteria only, but also on sedimentary structures and on stratigraphie context.