Micropaleontology 457977 190483112 2008-02-10T22:50:31Z Abyssal leviathin 611413 {{Nofootnotes|date=February 2008}} '''Micropaleontology''' (also sometimes spelled as '''micropalaeontology''') is that branch of [[paleontology]] which studies microfossils. '''Microfossils''' are [[fossils]] generally not larger than four [[millimeter]]s, and commonly smaller than one millimeter, the study of which requires the use of light or electron [[microscopy]]. Fossils which can be studied with the naked eye or low-powered magnification, such as a hand lens, are referred to as [[macrofossil]]s. Obviously, it can be hard to decide whether or not some organisms should be considered microfossils, and so there is no fixed size boundary. For example, some colonial organisms, such as [[bryozoa]] (especially the [[Cheilostomata]]) have relatively large [[colony (biology)|colonies]], but are classified on the basis of fine skeletal details of the tiny individuals of the colony. Most bryozoan specialists tend to consider themselves [[invertebrate paleontology|paleontologist]]s, rather than micropaleontologists, but many micropaleontologists also study bryozoa. In another example, many fossil [[genus|genera]] of [[Foraminifera]], which are protists, are known from shells (called "tests") that were as big as coins, such as the genus ''[[Nummulites]]''. '''Microfossils''' are a common feature of the [[geologic timescale|geological record]], from the [[Precambrian]] to the [[Holocene]]. They are most common in deposits of [[ocean|marine]] environments, but also occur in brackish water, fresh water and terrestrial [[sedimentary]] deposits. While every [[Kingdom (biology)|kingdom]] of [[prehistoric life|life]] is represented in the microfossil record, the most abundant forms are [[protist]] skeletons or cysts from the [[Chrysophyta]], [[Pyrrhophyta]], [[Sarcodina]], [[acritarch]]s and [[chitinozoa]]ns, together with [[pollen]] and [[spores]] from the [[vascular plant]]s. Micropaleontology can be roughly divided into four areas of study on the basis of microfossil composition: (a) [[calcareous]], as in [[coccolith]]s and [[foraminifera]], (b) [[phosphorus|phosphatic]], as in the study of some [[vertebrate]]s, (c) [[silicate|siliceous]], as in [[diatom]]s and [[radiolaria]], or (d) [[organic matter|organic]], as in the [[pollen]] and [[spores]] studied in [[palynology]]. This division reflects differences in the mineralogical and chemical composition of microfossil remains (and therefore in the methods of fossil recovery) rather than any strict [[scientific classification|taxonomic]] or [[ecological]] distinctions. Most researchers in this [[field research|field]], known as '''micropaleontologists''', are typically specialists in one or more [[taxonomy|taxonomic group]]s. == Calcareous microfossils == [[Calcareous]] [CaCO3] microfossils include [[Coccolith]]s, [[Foraminifera]], Calcareous [[dinoflagellate]]s, and [[Ostracod]]s (seed shrimp). == Phosphatic microfossils == [[Phosphorus compounds|Phosphatic]] microfossils include [[Conodont]]s (tiny oral structures of an extinct chordate group), some [[scolecodonts]] ("worm" jaws), [[Shark]] spines and teeth, and other [[Fish]] remains (collectively called "[[ichthyolith]]s"). == Siliceous microfossils == [[Silicate|Siliceous]] microfossils include [[Diatoms]], [[Radiolaria]], [[Silicoflagellate]]s, [[phytolith]]s, some [[scolecodonts]] ("worm" jaws), and [[spicule]]s. == Organic microfossils == The study of [[organic matter|organic]] microfossils is called [[palynology]]. Organic microfossils include [[pollen]], [[spores]], [[Chitinozoa]]ns (thought to be the egg cases of marine invertebrates), [[Scolecodonts]] ("worm" jaws), [[Acritarchs]], [[Dinoflagellate]] cysts, and [[fungal]] remains. == Methods == Sediment or rock samples are collected from either cores or outcrops, and the microfossils they contain extracted by a variety of physical and chemical laboratory techniques, including sieving, density separation by [[centrifuge]], and chemical digestion of the unwanted fraction. The resulting concentrated sample of microfossils is then mounted on a slide for analysis, usually by light microscope. Taxa are then identified and counted. The very large numbers of microfossils that a small sediment sample can often yield allows the collection of statistically robust datasets which can be subjected to [[multivariate statistics|multivariate]] analysis. A typical microfossil study will involve identification of a few hundred specimens from each of ten to a hundred samples. == Applications of Micropaleontology == Microfossils are especially noteworthy for their importance in [[biostratigraphy]]. Since microfossils are often extremely abundant, widespread, and quick to appear and disappear from the stratigraphic record, they constitute ideal [[index fossils]] from a biostratigraphic perspective. In addition, the [[planktonic]] and [[nektonic]] habits of some microfossils gives them the added bonus of appearing across a wide range of [[facies]] or paleoenvironments, and having near-global distribution making bio[[stratigraphic correlation]] even more powerful and effective. Microfossils also provide some of the most important records of global environmental change on long-timescales, particularly from deep-sea sediments. Across vast areas of the ocean floor the shells of planktonic micro-ogranisms sinking from surface waters provide the dominant source of sediment and they continuously accumulate (typically at rates of 20-50m/million years). Study of changes in assemblages of microfossils and of changes in their shell chemistry (e.g oxygen isotope composition) are fundamental to research on climate change in the geological past. In addition to providing an excellent tool for [[sedimentary rock]]-body dating and for paleoenvironmental reconstruction – heavily used in both [[petroleum]] [[geology]] and [[paleoceanography]] – micropaleontology has also found a number of less orthodox applications, such as its growing role in [[forensic]] police investigation or in provenancing archaeological artefacts. == References == * Brasier, M.D. (1980), ''Microfossils''. Chapman and Hall publishers. ISBN 0-412-44570-0 * Traverse, A. (1988), ''Paleopalynology''. Unwin Hyman ISBN 0-04-561001-0 == External links == * [http://www.nhm.ac.uk/hosted_sites/tms/ The Micropalaeontological Society] * [http://www.shef.ac.uk/uni/academic/N-Q/palysc/index.html Centre for Palynology, University of Sheffield, UK] * [http://www.palynology.org/ The American Association of Stratigraphic Palynologists (AASP)] * [http://www.shef.ac.uk/~cidmdp/ Commission Internationale de Microflore du Paléozoique (CIMP)], international commission for Palaeozoic palynology. * [http://www.nhm.ac.uk/hosted_sites/ina/ The International Nannoplankton Association] * [http://www.shef.ac.uk/~cidmdp/cimpsuba.html CIMP Subcommission on Acritarchs] * [http://www.shef.ac.uk/~cidmdp/cimpsubc.html CIMP Chitinozoan Subcommission] * [http://micropress.org/ Micropaleontology Press, a division of the Micropaleontology Project, a nonprofit organization with the mission of promoting the science of micropaleontology.] * [http://www.ucmp.berkeley.edu/collections/microhold.html University of California, Berkeley, microfossil collections.] * [http://www-odp.tamu.edu/mrc/mrcpage.HTML The Ocean Drilling Programme (ODP) Micropaleontological reference centres.] * [http://www.ucl.ac.uk/GeolSci/micropal/ University College, London, Micropalaeontology Unit, including the ''MIRACLE'' microfossil image database.] [[Category:Subfields of paleontology]] [[Category:Branches of botany]] [[Category:Archaeological sub-disciplines]] [[Category:Fossils]] [[de:Mikropaläontologie]] [[eu:Mikropaleontologia]] [[fr:Micropaléontologie]] [[hr:Mikropalentologija]] [[id:Mikropaleontologi]] [[it:Micropaleontologia]] [[nl:Micropaleontologie]] [[ja:微化石]] [[pl:Mikropaleontologia]] [[sk:Mikropaleontológia]]