Fossil record

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By analyzing the fossil record, u. a. the biodiversity of past geological ages (palaeobiodiversity) and thus extinction events can be reconstructed. The diagram shows the paleobiodiversity of marine life throughout the Phanerozoic .

The fossil record is the sum of all scientifically documented (i.e. described in publications ) occurrences of fossils in their stratigraphic context. The fossil record is the essential source of information on the development of life on earth. The summary study of the fossil record is the subject of analytical paleobiology , which is a branch of paleontology .

Since fossils are almost exclusively preserved in loose sediments and sedimentary rocks and the transmission of these deposits decreases exponentially with age due to weathering and erosion , the quality of the fossil record depends heavily on geological age . In general, the older the worse. In addition, there are fluctuations in the completeness of the geological tradition, because weathering, erosion and sedimentation are primarily controlled by tectonic activity (including mountain formation ) and sea ​​level fluctuations , which in turn are subject to cycles ( glacial eustasia as an expression of climate cycles , supercontinent cycles ). Furthermore, high tectonic activity in the affected sedimentary rocks, u. a. as a result of accompanying magmatic processes , to an intensification of diagenesis up to metamorphosis , which can result in the complete destruction of the fossil content. Older rocks also lie in undeformed, active and fossil sedimentary basins, often several 1000 meters underground, where they are difficult to access for research.

The fossil record on Earth begins about 3.5 billion years ago in the Archean with the first documented microfossils in Chert rock . But life can have arisen much earlier. Macrofossils are known from the most recent Neoproterozoic ( Ediacarian ). In the Cambrian , the so-called Cambrian Explosion began worldwide, a largely complete macrofossil tradition.

See also

literature

  • Michael J. Benton, David AT Harper: Introduction to Paleobiology and the Fossil Record. Wiley-Blackwell, Chichester Oxford 2009, ISBN 978-1-4051-8646-9 .
  • Ricard V. Solé, Mark Newman: Extinctions and Biodiversity in the Fossil Record. Pp. 297-301 in: Harold A. Mooney, Josep G. Canadell (Eds.): Encyclopedia of Global Environmental Change. Volume 2 - The Earth system: biological and ecological dimensions of global environmental change. John Wiley & Sons, Chichester 2002, ISBN 978-0-470-85361-0 .

Web links

  • The Paleobiology Database - Online database for the systematic recording of the fossil record
  • Fossilworks - Tools for statistical data analysis and downloading data from the Paleobiology Database