Editing Shale (section)

==As hydrocarbon source rock==
Shale is the most common [[source rock]] for hydrocarbons ([[natural gas]] and [[petroleum]]).<ref name=":0" /> The lack of coarse sediments in most shale beds reflects the absence of strong currents in the waters of the depositional basin. These might have oxygenated the waters and destroyed organic matter before it could accumulate. The absence of carbonate rock in shale beds reflects the absence of organisms that might have secreted carbonate skeletons, also likely due to an anoxic environment. As a result, about 95% of organic matter in sedimentary rocks is found in shales and other mudrocks. Individual shale beds typically have an organic matter content of about 1%, but the richest source rocks may contain as much as 40% organic matter.{{sfn|Blatt|Middleton|Murray|1980|pp=396-397}}

The organic matter in shale is converted over time from the original proteins, [[Polysaccharide|polysaccharides]], [[Lipid|lipids]], and other organic molecules to [[kerogen]], which at the higher temperatures found at greater depths of burial is further converted to [[graphite]] and petroleum.{{sfn|Blatt|Middleton|Murray|1980|pp=397}}