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Diamictite

From Wikipedia, the free encyclopedia
Type of sedimentary rock
Diamictite from Stolpe, eastern Germany
'Snowball Earth'-type diamictite from the Pocatello Formation,Idaho, United States
Boulder of diamictite of theMineral Fork Formation,Antelope Island,Utah, United States
Elatina Formation diamictite belowEdiacaranGSSP site in theFlinders Ranges NP, South Australia. A$1 coin for scale.

Diamictite (/ˈd.əmɪktt/; from Ancient Greekdia- (δια): 'through' andmeiktós (µεικτός): 'mixed') is a type of lithifiedsedimentary rock that consists of nonsorted to poorly sortedterrigenous sediment containing particles that range in size fromclay toboulders, suspended in amatrix ofmudstone orsandstone. The term was coined byRichard Foster Flint and others as a purely descriptive term, devoid of any reference to a particular origin.[1] Somegeologists restrict the usage to nonsorted or poorly sortedconglomerate orbreccia that consists of sparse,terrigenousgravel suspended in either a mud or sand matrix.[2]

Unlithified diamictite is referred to asdiamicton.

The term diamictite is often applied to nonsorted or poorly sorted, lithified glacial deposits such asglacial tillite andboulder clay, and diamictites are often mistakenly interpreted as having an essentiallyglacial origin (seeSnowball 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

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  1. ^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.
  2. ^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
  3. ^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)Archived 2007-11-28 at theWayback Machine
  4. ^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

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

External links

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Types of rocks
Igneous rock
Sedimentary rock
Metamorphic rock
Specific varieties
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