packstone
Under the Dunham classification (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, a packstone is defined as a grain-supported carbonate rock 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.