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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 .
The new thought is that these ocean currents were slowed by blooms of microscopic marine primary producers, which allowed for the settlement of organic-rich sediments at the seafloor, producing many of the economically productive black shale beds that are present today. To this day it remains an intensely researched subject by scholars and ...
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 ...
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.
The Rockwell Formation was described at its type section at Rockwell Run in West Virginia as soft arkosic sandstone, fine hard conglomerate, and buff hackly shale. [3]The formation was originally described in West Virginia by Stose and Swartz (1912). [3]
Source rocks are classified from the types of kerogen that they contain, which in turn governs the type of hydrocarbons that will be generated: [1]. Type I source rocks are formed from algal remains deposited under anoxic conditions in deep lakes: they tend to generate waxy crude oils when submitted to thermal stress during deep burial.