detrital

Detrital, in geology, is an adjective used to describe material derived from the mechanical breakdown of preexisting rocks (detritus). It is commonly applied to sediments and sedimentary rocks that are made up of clastic fragments transported from elsewhere, rather than precipitated from solution or formed by biological processes.

Detrital sediments form by weathering of rocks, erosion and transport of fragments by water, air, or ice, followed by deposition and lithification into rocks such as sandstone, siltstone, shale, conglomerate, and breccia. Grain size, sorting, and rounding reflect transport history and distance from source, while mineral composition indicates source rocks. Mature detrital deposits tend to be well sorted and well rounded with a predominance of stable minerals like quartz; immature detrital deposits may contain unstable feldspars and lithic fragments and show range of grain sizes.

Detrital rocks are distinguished from chemical sediments, which form by precipitation of dissolved minerals, and from biogenic or carbonate sediments. In geology, detrital materials are also studied for provenance, using features such as grain shapes, mineralogy, and isotopic compositions, including detrital zircon ages. Detrital rock analysis informs interpretations of past climates, tectonics, and sediment transport pathways.