Fossils and Fossilisation


Fossils are the recognisable remains or traces of activity of prehistoric life, typically defined as >10 000 years old. Pseudofossils are nonorganic objects that bear false resemblance to organism remains. The fossil record is strongly biased toward organisms with hard parts, such as mineralised skeletons of calcite, aragonite, phosphate, silica or refractory organic materials such as wood, that live in areas prone to pulses of sediment accumulation. Hence, preservation is not only particularly favoured in shallow offshore, storm‐affected and marine environments but also to a lesser extent, in the deep sea, lakes and river point bars. Occasionally, rapid burial in anoxic setting coupled with early mineralisation leads to extraordinarily preserved fossil Lagerstätten. The study of fossil preservation – taphonomy – is subdivided into biostratinomy and fossil diagenesis. Biostratinomic processes affect potential fossil remains between death and final burial, including decay of organic parts, disarticulation, fragmentation, abrasion, bioerosion and dissolution. Fossil diagenesis constitutes processes that affect organic remains subsequent to burial such as dissolution, compaction and early and late mineralisation. Taphonomy reveals biases of the fossil record and also provides insights into depositional rates and processes.

Key Concepts:

  • Fossils are prehistoric (>10 000 years), discrete remains or traces of behaviour of once‐living organisms.

  • Preservation in the fossil record is a rare event that generally requires organisms with ‘hard parts’ (mineralised or resistant organic skeletons) and entombment within sediments.

  • Extraordinary preservation of articulated skeletons and even soft parts requires very rapid burial, often associated with mass mortalities, in low oxygen sediments and various types of early diagenetic mineralisation.

  • A variety of settings may favour exceptional preservation, including storm‐influenced continental shelves, deeper marine environments and stagnant lagoons, freshwater lakes, including maars or volcanic lakes, caves, tar pits and permafrost.

  • The study of fossil preservation, taphonomy, is subdivided into biostratinomy and fossil diagenesis.

  • Biostratinomy comprises the study of all processes that affect potential fossils from the time of death, or production of a trace or sheddable structures (leaves, seed and exoskeletal parts), to final burial.

  • Biostratinomic processes include decay of soft parts, infilling by disarticulation of bivalved or multielement skeletons, breakage, bioerosion, abrasion, transport and chemical corrosion.

  • Fossil diagenesis includes compaction, early mineralisation of various sorts including infillings and/or replacements of pyrite, phosphate, and silica and late‐stage mineralisation including overgrowth of earlier‐formed minerals and major episodes of (sometimes selective) dissolution.

  • A combination of biostratinomic and diagenetic characteristics can aid in identifying taphonomically defined assemblages or taphofacies that may provide a ‘fingerprint’ of particular depositional environments.

Keywords: taphonomy; preservation; fossils; depositional environment; biostratinomy; burial; diagenesis; time‐averaging; palaeoecology

Figure 1.

Schematic showing the processes of fossilisation in a shallow marine seafloor environment. Living community occupies the water, sediment–water interface and the upper sediments. Burrowers, such as clams, churn the sediment and mix skeletal remains both downward and upward in the mixed layer. Once‐buried shells may be reworked (disinterred) and damaged or destroyed. Eventually, some remains become buried in the ‘historical layer’ (hist.) and may become part of the permanent geological record. Processes affecting organism remains up to the time of final burial fall in the realm of biostratinomy; geochemical processes occurring in the sediments including those long after burial are considered aspects of fossil diagenesis. Modified from Martin .

Figure 2.

Aspects of orientation of skeletal materials. (a) Shows response of shells to free settling. (b) Response to current flipping. (c) Wave or oscillatory currents orient elongate shells bimodally with the long axis parallel to wave propagation. (d) Unidirectional currents align conical or ellipsoidal objects parallel to the current and with the apex upcurrent; black silhouettes represent rose diagrams or circular histograms of compass orientations. (e) Various fabrics assumed by skeletons in response to currents (lower left) and waves; plan view of bedding surfaces; cross section shows fabrics of shells on the edges of beds of sediment. Adapted from Allen and Kidwell et al..

Figure 3.

Examples of fossil assemblages recording variable amounts of time before burial, based on samples from middle Devonian shales of western New York State. (a) Very low rate of deposition; note corroded and phosphatised (black) fossil debris. (b) Slow deposition; trilobites and brachiopod shells are disarticulated to somewhat fragmented; small corals and bryozoans are fragmented to somewhat corroded. (c) Mass mortality and rapid burial beneath a thin mud layer; delicate fossils such as the crinoid (in middle) are partially articulated but somewhat scrambled by burrowers. (d) Mass mortality and rapid burial (obrution) beneath a thicker mud layer preserving delicate crinoid (upper left) and trilobites intact; brachiopods (far right) and bryozoans (lower left) are buried in life position. Adapted from Brett and Baird .

Figure 4.

Moult ensemble of the trilobite Phacops saberensis, Lower Devonian, Morocco, showing disarticulated cephalon and articulated thorax‐pygidium; such associated moult parts provide evidence for a lack of seafloor disturbance at the time of burial and thereby provide strong evidence for life activities in the environment. Reproduced from Brett et al.. Reprinted by permission of Society for Sedimentary Geology.

Figure 5.

Distribution of selected taphonomic features on crinoid plates from the Copan crinoid Lagerstätte (Pennsylvanian) of Oklahoma. Note that encrustation and breakage show increases in thinner units, indicating intervals of slow sedimentation where disarticulated crinoid skeletons remained exposed in an oxygenated setting, allowing other organisms to utilise this material as substrata, and where breakage through microbial degradation or scavenging was enhanced. Interestingly, these units are also characterised by an increase in articulated crinoid crowns, indicating that the intervals of slow sedimentation were episodically interrupted by rapid, but thin and subtle, sedimentation events. This exemplifies the utility of taphofacies analysis, as the entire depicted interval is fairly uniform in terms of sediment character and presence/absence lists of organisms. Reproduced from Thomka et al..



Allen JRL (1990) Transport hydrodynamics: shells. In: Briggs DEG and Crowther PR (eds) Palaeobiology: A Synthesis, pp. 227–230. Oxford: Blackwell Scientific.

Allison PA (1986) Soft‐bodied animals in the fossil record: the role of decay in fragmentation during transport. Geology 14: 979–981.

Allison PA (1988) Konservat‐Lagerstätten: cause and classification. Paleobiology 14: 331–344.

Allison PA and Briggs DEG (1991) Taphonomy of nonmineralized tissues. In: Allison PA and Briggs DEG (eds) Taphonomy: Releasing the Data Locked in the Fossil Record, pp. 25–70. New York: Plenum Press.

Berner RA (1968) Calcium carbonate concretions formed by the decomposition of organic matter. Science 159: 195–197.

Berner RA (1980) Early Diagenesis: A Theoretical Approach. Princeton: Princeton University Press.

Bottjer DJ, Etter W, Hagadorn JW and Tang CM (eds) (2002) Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life. New York: Columbia University Press.

Brandt DS (1989) Taphonomic grades as a classification for fossiliferous assemblages. Palaios 4: 303–309.

Brett CE and Baird GC (1986) Comparative taphonomy: a key to paleoenvironmental interpretation based on fossil preservation. Palaios 1: 207–227.

Brett CE and Baird GC (eds) (1997) Paleontological Events: Stratigraphic, Ecological, and Evolutionary Implications. New York: Columbia University Press.

Brett CE and Bordeaux YL (1990) Taphonomy of brachiopods from a Middle Devonian shell bed: implications for the genesis of skeletal accumulations. In: MacKinnon L and Campbell L (eds) Brachiopods Through Time, pp. 219–226. Dunedin, New Zealand: Balkema Press.

Brett CE, Zambito JJ IV, Hunda BR and Schindler E (2012) Mid‐Paleozoic trilobite Lagerstätten: models of diagenetically enhanced obrution deposits. Palaios 27: 326–353.

Briggs DEG (2003) The role of decay and mineralization in the preservation of soft‐bodied fossils. Annual Review of Earth and Planetary Sciences 31: 275–301.

Briggs DEG and Wilby PR (1996) The role of calcium carbonate‐calcium phosphate switch in the mineralization of soft‐bodied fossils. Journal of the Geological Society of London 153: 665–668.

Bromley RG (1992) Bioerosion: eating rocks for fun and profit. In: Maples CG and West RR (eds) Trace Fossils, pp. 121–129. Paleontological Society Short Courses in Paleontology 5. Boulder: Paleontological Society Press.

Canfield DE and Raiswell R (1991) Carbonate precipitation and dissolution: its relevance to fossil preservation. In: Allison PA and Briggs DEG (eds) Taphonomy: Releasing the Data Locked in the Fossil Record, pp. 411–463. New York: Plenum Press.

Danise S, Dominici S and Betocchi U (2009) Mollusk species at a Pleistocene shelf whale fall (Orciano Pisano, Tuscany). Palaios 25: 449–456.

Dodson TM, Bakker RT, Behrensmeyer AK and McIntosh JS (1980) Taphonomy and paleoecology of the dinosaur beds of the Jurassic Morrison Formation. Paleobiology 6: 208–232.

Donovan SK (ed.) (1991) The Processes of Fossilization. New York: Columbia University Press.

Efremov JA (1940) Taphonomy: a new branch of paleontology. Pan‐American Geologist 74: 81–93.

Farrimond P and Eglinton G (1990) The record of organic components and the nature of source rocks. In: Briggs DEG and Crowther PR (eds) Palaeobiology: A Synthesis, pp. 217–222. Oxford: Blackwell Scientific.

Guthrie RD (1990) Frozen Fauna of the Mammoth Steppe. Chicago: University of Chicago Press.

James NP and Bourque A‐P (1992) Reefs and mounds. In: Walker RG and James NP (eds) Facies Models: Response to Sea Level Change, pp. 323–347. St. John's, Newfoundland: Geological Association of Canada Press.

Jia‐yu R and Johnson ME (1995) A stepped karst unconformity as an Early Silurian rocky shoreline in Guizhou Province (South China). Palaeogeography, Palaeoclimatology, Palaeoecology 121: 115–129.

Kidwell SM (1993) Patterns of time‐averaging in the shallow marine fossil record. In: Kidwell SM and Behrensmeyer AK (eds) Taphonomic Approaches to Time Resolution in Fossil Assemblages, pp. 275–300. Denver: Paleontological Society Short Courses in Paleontology 6.

Kidwell SM, Fürisch FT and Aigner T (1986) Conceptual framework for analysis and classification of fossil concentrations. Palaios 1: 228–238.

Kolbe SE, Zambito JJ IV, Brett CE, Wise JL and Wilson RD (2011) Brachiopod shell discoloration as an indicator of taphonomic alteration in the deep‐time fossil record. Palaios 26: 682–692.

Kowalewski M, Goodfriend GA and Flessa KW (1998) High‐resolution estimates of temporal mixing within shell beds: the evils and virtues of time‐averaging. Paleobiology 24: 287–304.

Kurtén B (1986) How to Deep‐Freeze a Mammoth. New York: Columbia University Press.

de Leeuw JW, Frewin NL, Van Bergen PF, Sinninghe Damsté JS and Collinson ME (1995) Organic carbon as a palaeoenvironmental indicator in the marine realm. In: Bosence DWJ and Allison PA (eds) Marine Palaeoenvironmental Analysis from Fossils, pp. 43–71. London: Geological Society Special Publication 83.

Lescinsky HL, Ledesma‐Vásquez J and Johnson ME (1991) Dynamics of Late Cretaceous rocky shores (Rosario Formation) from Baja California, Mexico. Palaios 6: 126–141.

Martin RE (1999) Taphonomy: A Process Approach. Cambridge: Cambridge University Press.

Parsons‐Hubbard K, Walker SE and Brett CE (eds) (2011) The Shelf and Slope Experimental Taphonomy Initiative (SSETI): Thirteen years of taphonomic observations on carbonate and wood in the Bahamas and Gulf of Mexico. Palaeogeography, Palaeoclimatology, Palaeoecology 312: 195–379.

Poinar GO Jr (1992) Life in Amber. Stanford: Stanford University Press.

Raiswell R and Fisher QJ (2004) Rates of carbonate cementation associated with sulphate reduction in DSDP/ODP sediments: implications for the formation of concretions. Chemical Geology 211: 71–85.

Richter R (1928) Aktuopaläontologie un Paläobiologie, eine Abgrenzung. Senckenbergiana 10: 285–292.

Rudwick MJS (1976) The Meaning of Fossils: Episodes in the History of Palaeontology, 2nd edn. New York: Science History Publications.

Schaal S and Ziegler W (1992) Messel – An Insight into the History of Life and the Earth. Oxford: Clarendon Press.

Scott AC and Rex G (1985) The formation and significance of Carboniferous coal balls. Philosophical Transactions of the Royal Society B: Biological Sciences 311: 123–137.

Seilacher A (1973) Biostratinomy: the sedimentology of biologically standardized particles. In: Ginsburg RD (ed.) Evolving Concepts in Sedimentology, pp. 159–177. Baltimore: Johns Hopkins University Press.

Seilacher A, Reif WE and Westphal F (1985) Sedimentological, ecological, and temporal patterns of fossil Lagerstätten. Philosophical Transactions of the Royal Society B: Biological Sciences 311: 5–23.

Selden P and Nudds J (2004) Evolution of Fossil Ecosystems. Chicago: University of Chicago Press.

Shabica CW and Hay AA (eds) (1997) Richardson's Guide to the Fossil Fauna of Mazon Creek. Chicago: Northeastern Illinois University Press.

Shäfer W (1972) Ecology and Palaeoecology of Marine Environments. Chicago: University of Chicago Press.

Speyer SE and Brett CE (1986) Trilobite taphonomy and Middle Devonian taphofacies. Palaios 1: 312–327.

Speyer SE and Brett CE (1991) Taphofacies controls: background and episodic processes in fossil assemblage preservation. In: Allison PA and Briggs DEG (eds) Taphonomy: Releasing the Data Locked in the Fossil Record, pp. 502–541. New York: Plenum Press.

Stock C and Harris JM (1992) Rancho La Brea: a record of Pleistocene life in California. Natural History Museum of Los Angeles County, Science Series 37: 1–113.

Taylor PD (1990) Preservation of soft‐bodied and other organisms by bioimmuration – a review. Palaeontology 33: 1–13.

Thomka JR, Mosher D, Lewis RD and Pabian RK (2012) The utility of isolated crinoid ossicles and fragmentary crinoid remains in taphonomic and paleoenvironmental analysis: an example from the Upper Pennsylvanian of Oklahoma, United States. Palaios 27: 465–480.

Vermeij GJ (1983) Traces and trends of predation, with special reference to bivalved animals. Palaeontology 26: 455–465.

Walker KR and Bambach RK (1971) The significance of fossil assemblages from fine‐grained sediments: time‐averaged communities. Geological Society of America Abstracts with Programs 3: 783–784.

Weigelt J (1927) Rezente Wirbeltierleichen und ihre Paläobiologische Bedeutung. Leipzig: Verlag von Max Weg.

Further Reading

Allison PA and Bottjer DJ (eds) (2011) Taphonomy, Second Edition: Process and Bias Through Time. New York: Springer.

Briggs DEG and Crowther PR (eds) (2001) Palaeobiology II. Oxford: Blackwell Science.

Kidwell SM and Behrensmeyer AK (eds) (1993) Taphonomic Approaches to Time Resolution in Fossil Assemblages. Paleontological Society Short Courses in Paleontology 6. Boulder: Paleontological Society Press.

Nagle JS (1967) Wave and current orientation of shells. Journal of Sedimentary Petrology 37: 1124–1138.

Nudds JR and Selden PA (2008) Fossil Ecosystems of North America: A Guide to the Sites and their Extraordinary Biotas. Chicago: University of Chicago Press.

Speyer SE and Brett CE (1988) Taphofacies models for epeiric sea environments: Middle Paleozoic examples. Palaeogeography, Palaeoclimatology, Palaeoecology 63: 222–262.

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Brett, Carlton E, and Thomka, James R(Feb 2013) Fossils and Fossilisation. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001621.pub2]