sedimentary geology ''Sedimentary Geology'' is a peer-reviewed scientific journal about sediments in a geological context published by Elsevier Elsevier () is a Dutch academic publishing company specializing in scientific, technical, and medical content. Its ...

, maturity describes the composition and texture of grains in

clastic rock Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

s, most typically

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s, resulting from different amounts of sediment transportation. A sediment is mature when the grains in a sediment become well-sorted and well-rounded due to

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

or abrasion of the grains during transport. There are two components to describe maturity, ''texture'' and ''composition''.

Texture Texture may refer to: Science and technology * Surface texture, the texture means smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface characteristics with waves shorter than road roughness * Texture (c ...

describes how rounded and sorted the sample is while composition describes how much the composition trends toward stable

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

s and components (often

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical fo ...

). A mature sediment is more uniform in appearance, for the sediment grains are well rounded, are of a similar size and exhibit little compositional variation. Conversely, an immature sediment contains more angular grains, diverse grain sizes, and is compositionally diverse. As the sediment is transported, the unstable minerals are abraded or dissolved to leave more stable minerals, such as

. Mature sediments, which contain stable minerals, generally have a smaller variety of minerals than immature sediments, which can contain both stable and unstable minerals. One measure of this maturity is the ZTR index which is a measure of the common resistant minerals found in ultra-weathered sediments:

zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of the ...

, tourmaline, and

rutile Rutile is an oxide mineral composed of titanium dioxide (TiO2), the most common natural form of TiO2. Rarer polymorphs of TiO2 are known, including anatase, akaogiite, and brookite. Rutile has one of the highest refractive indices at visibl ...

. A sediment sample from the lower (downstream) portions of a stream is likely to be more mature than one found upstream, since the original sediment has been subject to more abrasion as it travels downstream.

References

{{geology-stub Sedimentology https://pubs.geoscienceworld.org/sepm/jsedres/article-abstract/38/4/1326/96178 Basu, A. (1985). Reading provenance from detrital quartz. In Provenance of arenites (pp. 231-247). Springer, Dordrecht.

See also

References