Glossary

Diagenesis is the collective term for all physical, chemical, and biological changes that a sediment undergoes after its initial deposition and before the onset of metamorphism. Operating at temperatures generally below approximately 200 °C and pressures below roughly 300 MPa, diagenetic processes include compaction, cementation, dissolution, mineral replacement, recrystallization, and microbial activity. These processes reduce porosity, alter mineralogy, and ultimately transform unconsolidated sediment into lithified sedimentary rock—a transformation commonly termed lithification. In the context of taphonomy, diagenesis is of central importance because it governs how organic remains buried within sediment become chemically and structurally modified on the path to fossilization. Biological hard parts such as bone, teeth, and shells undergo diagenetic alteration through dissolution–recrystallization of their mineral phases, loss or replacement of organic components like collagen, and incorporation of extrinsic chemical elements from surrounding pore fluids. The nature and degree of diagenetic change are controlled by both intrinsic factors—such as the original composition, porosity, and microstructure of the buried material—and extrinsic factors including temperature, pore-fluid chemistry, pH, redox conditions, and burial depth. Understanding diagenesis is therefore essential for interpreting the fidelity of the fossil record, for geochemical and isotopic analyses of ancient organisms, and for evaluating reservoir quality in petroleum geology.

**Taphonomy** is the study of the processes by which organic remains pass from the biosphere into the lithosphere, encompassing all biological, chemical, and physical agents that preserve or destroy organic materials and affect information in the fossil record. The discipline was established in 1940 by Soviet paleontologist Ivan Efremov, who defined it as 'the study of the transition, in all its details, of animal remains from the biosphere into the lithosphere.' In 1985, Behrensmeyer and Kidwell broadened this definition to include all types of organic remains and traces—not only animal hard parts but also plants, microbes, biomolecules, trackways, and coprolites—and to recognize that both preservation and destruction of remains are legitimate objects of study. Taphonomy operates through three sequential but overlapping stages: necrology (early post-mortem decomposition and scavenging), biostratinomy (transport and burial), and diagenesis (post-burial chemical and physical alteration, including mineralization). Because these processes act as successive filters on biological information, taphonomic analysis is essential for identifying and correcting the preservation biases inherent in the fossil record—biases relating to body composition, habitat, organism size, and the time-averaging of assemblages. Beyond paleontology, taphonomy has become a profoundly interdisciplinary science with applications in archaeology, forensic anthropology, conservation paleobiology, ecology, and astrobiology, providing critical methodological frameworks for interpreting dead remains across all these fields.