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sedimentary geology Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of ...
, 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 b ...
s, most typically
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
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, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...
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 * Image texture, the spatial arrangement of color or intensities in an image * Surface texture, the smoothness, roughness, or bumpiness of the surface of an object * Texture (roads), road surface 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 substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
s and components (often
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
). 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
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
. 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 th ...
,
tourmaline Tourmaline ( ) is a crystalline silicate mineral, silicate mineral group in which boron is chemical compound, compounded with chemical element, elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a ...
, 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 vis ...
. 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.


See also

* Maturity (disambiguation)


References

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. {{Sedimentology-stub