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Diamictite



Diamictite (pronounced /ˌdaɪəˈmɪktaɪt/) is a non-sorted conglomerate with a wide range of clasts with up to 25% gravel sized (greater than 2 mm). Diamictites are composed of coarse, poorly sorted, angular to well rounded sedimentary clastic fragments, or other type of fragments (igneous and metamorphic rocks) supported by a typically argillaceous (clay sized) matrix.

Additional recommended knowledge

Diamictites are usually interpreted as having a glacial or ice sheet origin. The deposits are interpreted as originating as either unsorted end moraine glacial till or ice rafted sediments carried into marine environments and deposited by rapidly disintegrating ice sheets. The main characteristics of diamictite is the matrix that supporting the fragment, a phenomenon that only can be deposited by glacial or ice sheet origin.

There are two Neoproterozoic diamictite layers in Namibia, the Chuos and Ghaub formations, which have been extensively studied in support of the snowball earth hypothesis. The Chuos diamictite is marked the Sturtian glaciation around 710 Mya, while the Ghaub is the result of Marinoan glaciation (630 Mya). Both diamictites are deposited within continuous carbonate formations that imply a tropical marine environment. It is postulated that thick ice-sheets were developed during two phases in the Neoproterozoic that covered almost the entire Earth, including the tropical seas.[citation needed]

References

  • Deynoux, M., et al (Editors) (2004) Earth's Glacial Record, Cambridge University Press, pp. 34-39 ISBN 0-521-54803-9
  • British Geological Survey PDF
  • Illustration and definition


 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Diamictite". A list of authors is available in Wikipedia.
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