Principle of faunal succession

Principle of faunal succession

The principle of faunal succession is based on the observation that sedimentary rock strata contain fossilised flora and fauna, and that these fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances. A fossilised Neanderthal bone will never be found in the same stratum as a fossilised Megalosaurus, for example, because the two species lived during different geological periods, separated by many millions of years. This allows for strata to be identified and dated by the fossils found within.

This principle, first identified in the early 1790s by the geologist William Smith, is of great importance in determining the relative age of rocks and strata. [As recounted in Simon Winchester, "The Map that Changed the World" (New York: HarperCollins, 2001), pp. 59-91.] The fossil content of rocks together with the law of superposition helps to determine the time sequence in which sedimentary rocks were laid down.

The theory of evolution powerfully explains the causal mechanism of the observed faunal and floral succession preserved in rocks. Archaic biological features and organisms are succeeded in the fossil record by more modern versions. For instance, paleontologists investigating the evolution of birds predicted that feathers would first be seen in primitive forms on flightless predecessor organisms such as feathered dinosaurs. This is precisely what has been discovered in the fossil record: simple feathers, incapable of supporting flight, are succeeded by increasingly large and complex feathers. [http://www.nature.com/nature/journal/v420/n6913/fig_tab/nature01196_F5.html Mingke Yu, et. alia,"The morphogenesis of feathers", "Nature" 420, (21 November 2002), pp. 308-312] .]

In practice, the most useful diagnostic species are those with the fastest rate of species turnover and the widest distribution; their study is termed biostratigraphy, the science of dating rocks by using the fossils contained within them. In Cenozoic strata, fossilized tests of foraminifera are often used to determine faunal succession on a refined scale, each biostratigraphic unit (biozone) being a geological stratum that is defined on the basis of its characteristic fossil taxa. An outline microfaunal zonal scheme based on both foraminifera and ostracoda was compiled by M. B. Hart (1972).

References

ee also

*Law of superposition
*Principle of original horizontality
*Principle of lateral continuity
*Principle of cross-cutting relationships


Wikimedia Foundation. 2010.

Игры ⚽ Нужна курсовая?

Look at other dictionaries:

  • Faunal assemblage — is the archaeological or paleontological term for a group of associated animal fossils found together in a given stratum. The principle of faunal succession is used in biostratigraphy to determine each biostratigraphic unit, or biozone. The… …   Wikipedia

  • Principle of original horizontality — A stratigraphic section of Ordovician rock exposed in central Tennessee, USA. The sediments composing these rocks were formed in an ocean and deposited in horizontal layers …   Wikipedia

  • geochronology — geochronologic /jee oh kron l oj ik/, geochronological, adj. geochronologist, n. /jee oh kreuh nol euh jee/, n. the chronology of the earth, as based on both absolute and relative methods of age determination. [1890 95; GEO + CHRONOLOGY] * * *… …   Universalium

  • dating — I In geology and archaeology, the process of determining an object s or event s place within a chronological scheme. Scientists may use either relative dating, in which items are sequenced on the basis of stratigraphic clues (see stratigraphy) or …   Universalium

  • Georges Cuvier — Born August 23, 1769(1769 08 …   Wikipedia

  • Law of superposition — The law of superposition (or the principle of superposition) is a key axiom based on observations of natural history that is a foundational principle of sedimentary stratigraphy and so of other geology dependent natural sciences: The principle… …   Wikipedia

  • Fossil — For other uses, see Fossil (disambiguation). Three small ammonite fossils, each approximately 1.5 cm across …   Wikipedia

  • Cross-cutting relationships — Cross cutting relations can be used to determine the relative ages of rock strata and other geological structures. Explanations: A folded rock strata cut by a thrust fault; B large intrusion (cutting through A); C erosional angular unconformity… …   Wikipedia

  • Geology — Oceanic crustContinental Crust] Geology (from Greek: γη, gê , earth ; and λόγος, logos , speech lit. to talk about the earth) is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the… …   Wikipedia

  • Stratigraphy — Stratigraphy, a branch of geology, studies rock layers and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy includes two related subfields: lithologic or lithostratigraphy and… …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”