clastklaste

Clastklaste is a geological term used to describe a fragment of pre-existing rock that has been incorporated into a sediment or into another rock. The concept underpins clastic geology, where rocks are built up from pieces of older rocks that have been broken, transported, and deposited. The word reflects a general idea of a broken piece, with the root from Greek klastos meaning broken.

In clastic rocks, clasts are the principal constituents. They can be quartz-rich grains, feldspar-rich fragments, or lithic fragments made of various rock types. Clasts occur in a range of sizes from fine gravel to large boulders and may be angular or rounded depending on the extent of transport and abrasion. The composition and texture of clasts offer information about the source region (provenance), transport pathways, and depositional conditions.

Clasts are often categorized by their origin within a sediment. Extraclasts are clasts that originated outside the depositional body and were brought in by transport processes. Intraclasts are derived from within the same sedimentary unit, formed by weathering or dissolution of surrounding material during diagenesis. Lithoclasts refer to clasts whose lithology is significant for interpreting the rock’s history, while mineral-specific clasts (such as quartz clasts) point to particular source terrains.

Studying clasts involves measuring their size distribution, roundness, and mineralogy. Such analyses help reconstruct paleoenvironments, transport energy, weathering intensity, and diagenetic histories. Clast characteristics also aid in classifying clastic rocks and in determining provenance, tectonic setting, and sedimentary processes.

See also: clastic rock, sandstone, conglomerate, provenance, lithology.