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Under the
Dunham classification The Dunham classification system for carbonate sedimentary rocks was originally devised by Robert J. Dunham in 1962, and subsequently modified by Embry and Klovan in 1971 to include coarse-grained limestones and sediments that had been organical ...
(Dunham, 1962Dunham, R.J. (1962) Classification of carbonate rocks according to depositional texture. In: Classification of Carbonate Rocks (Ed. W.E. Ham), Am. Assoc. Pet. Geol. Mem., 1, 108–121.) system of
limestones Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms when t ...
, a packstone is defined as a grain-supported
carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as dolosto ...
that contains 1% or more mud-grade fraction. This definition has been clarified by Lokier and Al Junaibi (2016){{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 as ''a carbonate-dominated lithology containing carbonate mud (<63 μm) in a fabric supported by a sand grade (63 μm to 2 mm) grain-size fraction and where less than 10% of the volume consists of grains >2 mm''.


The identification of packstone

A study of the adoption and use of carbonate classification systems by Lokier and Al Junaibi (2016) identified three common problems encountered when describing a packstone: * Failure to identify the fabric as supported by the sand grade grain-size fraction - resulting in misidentification as wackestone. * Packstones with very small volumes of carbonate mud may be misclassified as grainstone. * Incorrectly estimating the volume of the component grains >2 mm.


References

Limestone