Diagenesis
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Diagenesis is the process of physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and tempe
A form of diagenesis is permineralization, in which buried organisms are replaced by minerals. These trilobites (Lloydolithus) were replaced by pyrite during a specific type of permineralization called pyritization.
Originally calcitic crinoid stem (in cross-section) diagenetically replaced by marcasite in a siderite concretion; Lower Carboniferous.
Kerogen
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Kerogen is solid, insoluble organic matter in sedimentary rocks. It consists of a variety of organic materials, including dead plants, algae, and other microorganisms, that have been compressed and he
Kerogen can be found in oil shale
