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Arkose (/ ˈ ɑːr k oʊ s,-k oʊ z /) or arkosic sandstone [1] is a detrital sedimentary rock, specifically a type of sandstone containing at least 25% feldspar. [ 2 ] [ 3 ] Arkosic sand is sand that is similarly rich in feldspar, and thus the potential precursor of arkose.
If the abundances of quartz, feldspars and rock fragments indicate that the rock is an arkose, a subarkose or a lithic arkose, one must then normalize the abundance of feldspars to 100% and attempt to identify the relative abundances of K-feldspars to plagioclase in the sample. If there is more plagioclase than there is K-feldspar, the rock is ...
Since it refers to grain size rather than chemical composition, the term is used for example in the classification of clastic carbonatic limestones, as the granulometrically equivalent term sandstone is not appropriate for limestone. Other arenites include sandstones, arkoses, greensands, and greywackes.
Arkose is a sand or sandstone with considerable feldspar content, derived from weathering and erosion of a (usually nearby) granitic rock outcrop. Some sands contain magnetite, chlorite, glauconite, or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts and obsidian.
The Dawson Arkose is a geologic formation in the Denver Basin that underlies the Denver area in Colorado. It is characterized by alternating beds of arkosic sandstone and mudstone . [ 1 ] [ 3 ] The Dawson Arkose contains plant remains [ 4 ] and other nonmarine fossils , and hosts aquifers that are important sources of water for the area.
Grus sand and granitoid. Grus is an accumulation of angular, coarse-grained fragments (particles of sand and gravel) resulting from the granular disintegration by the processes of chemical and mechanical weathering of crystalline rocks (most notably granitoids) generally in an arid or semiarid region. [1]
The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
Uluru is dominantly composed of coarse-grained arkose (a type of sandstone characterised by an abundance of feldspar) and some conglomerate. [ 46 ] [ 51 ] Average composition is 50% feldspar, 25–35% quartz and up to 25% rock fragments; most feldspar is K-feldspar with only minor plagioclase as subrounded grains and highly altered inclusions ...