Diamictite

Diamictite ( /ˈd.əmɪktt/; from Ancient Greek δια (dia-): through and µεικτός (meiktós): mixed) is a type of lithified sedimentary rock that consists of nonsorted to poorly sorted terrigenous sediment containing particles that range in size from clay to boulders, suspended in a matrix of mudstone or sandstone. The term was coined by Richard Foster Flint and others as a purely descriptive term, devoid of any reference to a particular origin.[1] Some geologists restrict the usage to nonsorted or poorly sorted conglomerate or breccia that consists of sparse, terrigenous gravel suspended in either a mud or sand matrix.[2]

Diamictite from Stolpe, eastern Germany
'Snowball Earth'-type diamictite from the Pocatello Formation, Idaho, United States
Boulder of diamictite of the Mineral Fork Formation, Antelope Island, Utah, United States
Elatina Formation diamictite below Ediacaran GSSP site in the Flinders Ranges NP, South Australia. A$1 coin for scale.

Unlithified diamictite is referred to as diamicton.

The term diamictite is often applied to nonsorted or poorly sorted, lithified glacial deposits such as glacial tillite and boulder clay, and diamictites are often mistakenly interpreted as having an essentially glacial origin (see Snowball Earth). The most common origin for diamictites, however, is deposition by submarine mass flows like turbidites and olistostromes in tectonically active areas, and they can be produced in a wide range of other geological conditions. Possible origins include:[3][4]


References

Further reading

  • Deynoux, M., et al. (Editors) (2004) Earth's Glacial Record, Cambridge University Press, pp. 34–39 ISBN 0-521-54803-9
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