Under the Dunham classification (Dunham, 1962Dunham, R.J., 1962. Classification of carbonate rocks according to depositional texture. In: W.E. Ham (Ed.), Classification of Carbonate Rocks. American Association of Petroleum Geologists Memoir. American Association of Petroleum Geologists, Tulsa, Oklahoma, pp. 108–121.) system of limestones, a wackestone is defined as a mud-supported carbonate rock that contains greater than 10% grains. Most recently, this definition has been clarified as a carbonate-dominated rock in which the carbonate mud (<63 μm) component supports a fabric comprising 10% or more very fine-sand grade (63 μm) or larger grains but where less than 10% of the rock is formed of grains larger than sand grade (>2 mm).
The identification of wackestone
A study of the adoption and use of carbonate classification systems by Lokier and Al Junaibi (2016) highlighted that the most common problem encountered when describing a wackestone is to incorrectly estimate the volume of 'grains' in the sample – in consequence, misidentifying wackestone as mudstone or vice versa. The original Dunham classification (1962) defined the matrix as clay and fine-silt size sediment <20 μm in diameter. This definition was redefined by Embry & Klovan (1971)Embry, A.F. and Klovan, J.E., 1971. A Late Devonian reef tract on Northeastern Banks Island, NWT. Bulletin of Canadian Petroleum Geology, 19(4)), 730–781. to a grain size of less than or equal to 30 μm. Wright (1992)Wright, V.P., 1992. A revised classification of limestones. Sedimentary Geology, 76(3–4), 177–185. proposed a further increase to the upper limit for the matrix size in order to bring it into line with the upper limit for silt (62 μm).
See also Wacke
References
External links http://strata.geol.sc.edu/thinsections/Carbonate-glossary.html