Dunham classification

Dunham classification A widely used limestone classification, proposed by Robert Dunham in 1962, which divides limestones on the basis of their texture and mud content. For limestones which retain their original, depositional texture, the main subdivisions are: lime mudstone (limestone with less than 10% grains in a mud-supported sediment); lime wackestone (limestone with more than 10% grains in a mud-supported sediment); lime packstone (grain-supported limestone with mud matrix between the grains); lime grainstone (grain-supported limestone with no mud matrix); and lime boundstone (limestone whose original components were bound together (e.g. by corals or algae) during deposition). For limestones in which the depositional texture has been destroyed by recrystallization, Dunham defines two types: crystalline limestone (recrystallized limestone with a fine texture); and sucrosic limestone (recrystallized limestone with a coarse texture). The original Dunham classification does not subdivide limestones with particles coarser than 2 mm, or differentiate between different types of organically bound limestone. These categories of limestone are defined by Embry and Clovan in their modifications to the Dunham classification. See EMBRY AND CLOVAN CLASSIFICATION.