{{short description|Mud-supported carbonate rock that contains greater than 10% grains}} thumb|Fragmented bioclastic wackestone thumb|A Wackestone in thin section (width of image is 10 mm) Under the Dunham classification (Dunham, 1962<ref name=":0">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.</ref>) 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)''.<ref name=":1">{{Cite journal|last=Lokier|first=Stephen W.|last2=Al Junaibi|first2=Mariam|date=2016-12-01|title=The petrographic description of carbonate facies: are we all speaking the same language?|journal=Sedimentology|language=en|volume=63|issue=7|pages=1843–1885|doi=10.1111/sed.12293|issn=1365-3091|doi-access=free}}</ref>

== The identification of wackestone ==

[[File:Wackestone.svg|thumb|350px|Schematic wackestone as seen in thin section under the petrographic microscope.

Type of carbonaceous rock according to the depositional texture:

Alloctonous carbonates – Original components not bound at the deposition time. Less than 10% of components larger than sand size (> 2&nbsp;mm) Contains carbonate mud (micrite, silt/clay size <63 μm) Fabric supported by carbonate mud (micrite, <63 μm) 10% or more composed of 63 μm or greater grains

Legend:

Dotted background: micritic matrix. Curved blue particles: bioclasts (indeterminate fossils, e.g. bivalve fragments). Blue cones: bioclasts (e.g. fossils of gastropods) Black spheroids: bioclasts (pellets). ]]

A study of the adoption and use of carbonate classification systems by Lokier and Al Junaibi (2016)<ref name=":1" /> 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)<ref name=":0" /> defined the matrix as clay and fine-silt size sediment <20 μm in diameter. This definition was redefined by Embry & Klovan (1971)<ref>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.</ref> to a grain size of less than or equal to 30 μm. Wright (1992)<ref>Wright, V.P., 1992. A revised classification of limestones. Sedimentary Geology, 76(3–4), 177–185.</ref> 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== <references />

==External links== * http://strata.geol.sc.edu/thinsections/Carbonate-glossary.html {{Webarchive|url=https://web.archive.org/web/20070707215642/http://strata.geol.sc.edu/thinsections/Carbonate-glossary.html |date=2007-07-07 }}

{{Dunham classification rocks}} {{Rock type}}

Category:Limestone

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