Diamictite ( /ˈdaɪ.əmɪktaɪt/; from Greek δια (dia-): through and µεικτός (meiktós): mixed) is a classification of sedimentary rock distinguished by a high consistency of stones, gravel size or larger, up to 25%, so thouroughly mixed and various in form that they can only be classified into the unsortable group. Diamictite is compressed diamicton which simply means naturally occuring sediment, with a high content of stones, but of various rock types mixed together.
In geology, this may be termed a poorly or non-sorted conglomerate or breccia with a wide range of clasts,[1] up to 25% of them gravel sized (greater than 2 cm). Diamictites are composed of coarse, angular to well rounded sedimentary clastic fragments, or other type of fragments (igneous and metamorphic rocks) supported by a typically argillaceous (clay sized) matrix.
The term was coined in 1960 by Flint and others as a purely descriptive term for poorly sorted and laminated rocks, avoiding any reference to a particular origin.[2]
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:[3][4]