There are two widely used limestone classifications, those of Dunham (1962) and Folk (1959, 1962). The simplest descriptive classification is that of Dunham, where rocks are assigned names according to their depositional texture (312). This is primarily related to the energy of the depositional environment. The boundstone category, embracing sediments such as stromatolites and reef rocks which are bound into solid masses as they grow, has been subdivided, but these divisions are best recognised by large-scale hand-specimen and outcrop-sized features and are not considered here. The problems with the Dunham classification lie in the timing of introduction and origin of carbonate mud in packstones and the distinction of grain-and matrixsupported textures, as discussed by Tucker & Wright (1990). The classification is based on depositional texture and it is often difficult, if not impossible, to determine whether carbonate mud in a packstone was introduced at the time of deposition or subsequently infiltrated a primary grainstone.