Under the Dunham classification (Dunham, 1962) 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) to a grain size of less than or equal to 30 μm. Wright (1992) 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).
- Dunham, 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.
- Lokier, Stephen W.; Al Junaibi, Mariam (2016-12-01). "The petrographic description of carbonate facies: are we all speaking the same language?". Sedimentology. 63 (7): 1843–1885. doi:10.1111/sed.12293. ISSN 1365-3091.
- 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.
- Wright, V.P., 1992. A revised classification of limestones. Sedimentary Geology, 76(3–4), 177–185.