Under the

Dunham classification The Dunham classification system for carbonate sedimentary rocks Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentati ...

(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 th ...

, 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 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. Amer ...

. * Packstones with very small volumes of carbonate mud may be misclassified as

grainstone Under the Dunham classification (Dunham, 1962) system of limestones, a grainstone is defined as a grain-supported carbonate rock that contains less than 1% mud-grade material. This definition has recently been clarified as ''a carbonate-dominated ...

. * Incorrectly estimating the volume of the component grains >2 mm.

References

Limestone