Biostratinomy

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Conceptual relationships of biostratinomic processes (yellow) with paleoecology and necrology (green) and fossildiagenesis (orange). States of taphonomic preservation.svg
Conceptual relationships of biostratinomic processes (yellow) with paleoecology and necrology (green) and fossildiagenesis (orange).

Biostratinomy is the study of the processes that take place after an organism dies but before its final burial. It is considered to be a subsection of the science of taphonomy, along with necrology (the study of the death of an organism) and diagenesis (the changes that take place after final burial). These processes are largely destructive, and include physical, chemical and biological effects:

For the vast majority of organisms, biostratinomic destruction is total. However, if at least a few remnants of an organism make it to final burial, a fossil may eventually be formed unless destruction is completed by diagenesis. As the processes of biostratinomy are often dominated by sedimentological factors, analysis of the biostratinomy of a fossil can reveal important features about the physical environment it once lived in. The boundaries between the three disciplines within taphonomy are partly arbitrary. In particular, the role of microbes in sealing and preserving organisms, for example in a process called autolithification, is now recognised to be a very important and early event in the preservation of many exceptional fossils, often taking place before burial. Such mineralogical changes might equally be considered to be biostratinomic as diagenetic.

A school of investigation called aktuopaläontologie, subsisting largely in Germany, attempts to investigate biostratinomic effects by experimentation and observation on extant organisms. William Schäfer's book "Ecology and palaeoecology of marine environments" is a classic product of this sort of investigation. More recently, D.E.G. Briggs and colleagues have made detailed studies of decay with the prime aim of understanding the profound halt to these processes that is required by exceptional preservation in lagerstätten.

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Derek Ernest Gilmor Briggs is an Irish palaeontologist and taphonomist based at Yale University. Briggs is one of three palaeontologists, along with Harry Blackmore Whittington and Simon Conway Morris, who were key in the reinterpretation of the fossils of the Burgess Shale. He is the Yale University G. Evelyn Hutchinson Professor of Geology and Geophysics, Curator of Invertebrate Paleontology at Yale's Peabody Museum of Natural History, and former Director of the Peabody Museum.

The following outline is provided as an overview of and topical guide to ecology:

The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 40 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Additional sites with a similar form of preservation are known from the Ediacaran and Ordovician periods.

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Most fossils represent mineralized material such as bone or shells. However, biopolymers such as chitin and collagen can sometimes leave fossils – most famously in Burgess Shale type preservation and palynomorphs. The preservation of soft tissue is not as rare as sometimes thought.

Egg taphonomy Study of the decomposition and fossilization of eggs

Egg taphonomy is the study of the decomposition and fossilization of eggs. The processes of egg taphonomy begin when the egg either hatches or dies. Eggshell fragments are robust and can often travel great distances before burial. More complete egg specimens gradually begin to fill with sediment, which hardens as minerals precipitate out of water percolating through pores or cracks in the shell. Throughout the fossilization process the calcium carbonate composing the eggshell generally remains unchanged, allowing scientists to study its original structure. However, egg fossils buried under sediments at great depth can be subjected to heat, pressure and chemical processes that can alter the structure of its shell through a process called diagenesis.

References

  1. Fernández López, S.R. (2000). Temas de Tafonomía . Department of Paleontology, Complutense University of Madrid. 167 pages. (in Spanish)

Further reading