Keyword Definition

Clastic sedimentary rock consisting of less than 30 percent gravel-size (2 mm) particles and with a mud to sand ratio greater than 1.


Distinction of intrabasinal, diagenetic, or clastic genesis for very fine-grained carbonate minerals is interpretive in many cases. If there is uncertainty on the mudstone category based on intrabasinal vs epiclastic distinction required for clastic sedimentary rock-carbonate sedimentary rock categorization in this system, it is recommended to use the generic_mudstone category. Schnurrenberger, D., Russell, J. and Kelts, K., 2003, Classification of lacustrine sediments based on sedimentary components: Journal of Paleolimnology, v.29, p141-154.

This category is the union of the various fields labeled 'mudstone' with various qualifiers in Folk, 1954, Figure 1a, although Folk's (1954) category labeled 'mudstone' is a much more restricted category. The CGI category is equivalent to category labeled 'Mudrock' in SLTTs (2004), not to the category labeled 'Mudstone' adopted by that system from Folk (1954).

Pettijohn et al. 1987 referenced in Hallsworth & Knox 1999.

See Also: argillite

Parents: Clastic sedimentary rock (59); Generic mudstone (118)

Children: Claystone (61); Shale (236); Siltstone (241)

[Description taken from GeoSciML SimpleLithology201012.rdf]

Hierarchical classification

Sample >> Lithosphere >> Rock >> Whole >> Rock >> Sedimentary >> Generic mudstone >> Mudstone


Claystone | Shale | Siltstone

Category: Analysed material

The different kinds of sample material collected in the field have been classified hierarchically. Examples: “till”, “soil”, “vegetation”. Taken from the “Sample_Types_SHARED” database table.

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