Klastogeneesi

Klastogeneesi, also known as clastogenesis, is the process by which rock fragments, or clasts, are generated from preexisting rock. It encompasses the mechanical breakup and chemical degradation that release fragments of various sizes from larger lithic sources, followed by their transport and deposition as clastic material. The primary mechanism is weathering, including physical processes such as freeze-thaw fragmentation, thermal expansion, abrasion, and biological activity, often complemented by chemical weathering that weakens rock integrity. The result is clasts ranging from boulders to grains.

Klastogeneesi is a central concept in sedimentology and stratigraphy because the characteristics of clasts—size, shape, roundness, sorting, and mineral composition—control the properties of clastic sediments and sedimentary rocks like conglomerates and sandstones. Clast formation occurs in source areas (weathering zones) and during transport; subsequent processes (sorting, rounding) modify clasts before final deposition.

Analytical methods include grain-size analysis, petrographic examination, and morphometric assessments of shape and rounding. Field indicators such as quarrying, outcrop fragmentation, and clast distributions help distinguish primary clast production from in-situ fragmentation during deposition.

Etymology: from Greek klastos “broken” and genesis “origin.” Klastogeneesi is distinct from lithogenesis (origin of rocks) and diagenesis (post-depositional changes) though it interacts with these processes in the development of sedimentary records.