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Shale is characterized by its tendency to split into thin layers less than one centimeter in thickness. This property is called fissility. [1] Shale is the most common sedimentary rock. [2] The term shale is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the narrower sense of clay-rich fissile mudrock. [3]
The effect of bioturbation has been documented well in shale cores sampled: past variable critical depths where burrowing organisms can no longer survive, shale fissility will become more pervasive and better defined. Fissility is used by some geologists as the defining characteristic which separates mudstone (no fissility) from shale (fissile ...
The argillites grade into shale when the fissile layering typical of shale is developed. Another name for poorly lithified argillites is mudstone . [ citation needed ] These rocks, although variable in composition, are typically high in aluminium and silica with variable alkali and alkaline earth cations .
Marcellus Shale, New York. Shale is a fine grained, hard, laminated mudrock, consisting of clay minerals, and quartz and feldspar silt. Shale is lithified and cleavable. It must have at least 50-percent of its particles measure less than 0.062 mm. This term is confined to argillaceous, or clay-bearing, rock.
Two recognized types of intraformational conglomerates are shale-pebble and flat-pebble conglomerates. [6] A shale-pebble conglomerate is a conglomerate that is composed largely of clasts of rounded mud chips and pebbles held together by clay minerals and created by erosion within environments such as within a river channel or along a lake ...
Red beds (or redbeds) are sedimentary rocks, typically consisting of sandstone, siltstone, and shale, that are predominantly red in color due to the presence of ferric oxides. Frequently, these red-colored sedimentary strata locally contain thin beds of conglomerate , marl , limestone , or some combination of these sedimentary rocks.
In geology, a mixture of both silt and clay is called mud. Rocks that possess large amounts of both clay and silt are called mudstones. In some cases the term shale is also used to refer to mudrocks and is still widely accepted by most. However, others have used the term shale to further divide mudrocks based on the percentage of clay constituents.
F=f(Sh, A, R, Sp, T) where f denotes a functional relationship between these terms and where Sh denotes the shape, Sp the sphericity and T the micro-scale surface texture. [ 2 ] An example of this practical use has been applied to the roundness of the grains in the Gulf of Mexico in order to observe the distance from the source rocks.