Diamictite

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

Diamictite (/ˈdaɪ.əmɪktaɪt/; from Greek δια (dia-): through and µεικτός (meiktós): mixed) is a type of sedimentary rock that consists of a wide range of lithified, nonsorted to poorly sorted, terrigenous sediment, i.e. sand or larger size particles that are suspended in a mud matrix. Although the term diamictite is often used for poorly sorted, lithified glacial deposits, this term is applied to this type of sedimentary rock of any origin.[1][2] This term was coined in 1960 by Flint and others as a purely descriptive term for poorly sorted sedimentary rocks that contain a wide range of particle sizes and avoids any reference to a particular origin.[3] Some Earth scientists restrict the usage of this term to poorly or non-sorted conglomerate or breccia, which consists of sparse, terrigenous gravel suspended in either a mud or sand matrix.[4] The unlithified equivalent of a diamictite is known either as a diamicton or diamict.[2][4]

Diamictites are often interpreted mistakenly as having an essentially glacial origin (see Snowball Earth), but the most common origin of diamictites 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 formation conditions. Possible origins include:[5][6]


References

  1. ↑ Jackson, J.A., J. Mehl, and K. Neuendorf (2005) Glossary of Geology American Geological Institute, Alexandria, Virginia. 800 pp. ISBN 0-922152-76-4
  2. ↑ 2.0 2.1 Bennett, M.R., and N.F. Glasser (2009) Glacial Geology: Ice Sheets and Landforms, 2nd Ed. John Wiley & Sons, Ltd., New York, New York. 400 pp. ISBN 978-0-470-51691-1
  3. ↑ Flint, R.F., J.E. Sanders, and J. Rodgers (1960) Diamictite, a substitute term for symmictite Geological Society of America Bulletin. 71(12):1809–1810.
  4. ↑ 4.0 4.1 Tucker, M.E. (2003) Sedimentary Rocks in the Field John Wiley & Sons, Ltd., New York, New York. 244 pp. ISBN 978-0-470-85123-4
  5. ↑ Eyles, N.; Januszczak, N. (2004). "’Zipper-rift’: A tectonic model for Neoproterozoic glaciations during the breakup of Rodinia after 750 Ma". Earth-Science Reviews 65 (1-2): 1-73. (pdf 4 Mb)
  6. ↑ Huber, H., Koeberl, C., McDonald, I., Reimold, W.U.: Geochemistry and petrology of Witwatersrand and Dwyka diamictites from South Africa: Search for an extraterrestrial component. Geochimica et Cosmochimica Acta, Vol. 65, No. 12, pp. 2007–2016, 2001. (pdf 470 Kb)

Further reading

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

External links

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