Klastiska

Klastiska is the Swedish term used in geology to describe sedimentary rocks composed predominantly of fragments, or clasts, derived from pre-existing rocks. The term is the Swedish equivalent of “clastic” and derives from Greek klastos, meaning broken. Klastiska rocks are formed when weathered and eroded fragments are transported, deposited, and lithified through compaction and cementation. Their texture and composition reflect their source material and transport history.

Klastiska rocks are typically categorized by grain size: fine-grained varieties such as shale and siltstone; medium-grained varieties such as sandstone; and coarse-grained varieties such as conglomerate and breccia. Their characteristics—sorting (uniformity of grain size), rounding (shape of grains), and the minerals that cement them (for example calcite, silica, or iron oxides)—influence properties like strength, porosity, and permeability.

Klastiska rocks contrast with chemical sedimentary rocks, which form from mineral precipitation, and organic sedimentary rocks, which originate from accumulated plant or animal remains. Common examples of klastiska rocks include sandstone, shale, siltstone, conglomerate, and breccia. Under a depositional framework, the presence and arrangement of clasts, bedding features, and sedimentary structures help interpret past environments and transport processes, such as rivers, deltas, beaches, or continental margins.

See also: sedimentary rocks, clastic vs non-clastic, lithification.