Wikipedia

Palynology

Palynologyis the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur insediments,sedimentary rocks,and even some metasedimentary rocks.Palynomorphsare the microscopic, acid-resistant organic remains and debris produced by a wide variety ofplants,animals,andProtistathat have existed since the lateProterozoic.[2][3]

Pinepollenunder the microscope
A lateSiluriansporangiumbearingtrilete spores.Such spores provide the earliest evidence of life on land.[1]Green:A spore tetrad.Blue:A spore bearing a trilete mark – the Y-shaped scar. The spores are about 30–35 μm across.

It is the science that studies contemporary and fossilpalynomorphs(paleopalynology), includingpollen,spores,orbicules,dinocysts,acritarchs,chitinozoansandscolecodonts,together withparticulate organic matter(POM) andkerogenfound insedimentaryrocks andsediments.Palynology does not includediatoms,foraminiferansor other organisms withsiliceousorcalcareoustests.The name of the science and organisms is derived from the Greek‹See Tfd›Greek:παλύνω,translit.palynō,"strew, sprinkle" and-logy) or of "particles that are strewn".[3][4]

Palynology is an interdisciplinary science that stands at the intersection ofearth science(geologyor geological science) andbiological science(biology), particularlyplant science(botany).Biostratigraphy,a branch ofpaleontologyandpaleobotany,involvesfossilpalynomorphs from thePrecambrianto theHolocenefor their usefulness in therelative datingand correlation of sedimentarystrata.Palynology is also used to date and understand the evolution of many kinds of plants and animals. Inpaleoclimatology,fossil palynomorphs are studied for their usefulness in understanding ancient Earth history in terms of reconstructingpaleoenvironmentsand paleoclimates.[3][4]

Palynology is quite useful in disciplines such asarcheology,in honey production, andcriminalandcivil law.[3][4]In archaeology, palynology is widely used to reconstruct ancient paleoenvironments and environmental shifts that significantly influenced past human societies and reconstruct the diet of prehistoric and historic humans.Melissopalynology,the study of pollen and other palynomorphs inhoney,identifies the sources of pollen in terms of geographical location(s) andgeneraof plants. This not only provides important information on theecologyof honey bees, it also an important tool in discovering and policing the criminal adultriation and mislabeling of honey and its products.Forensic palynologyuses palynomorphs as evidence in criminal and civil law to prove or disprove a physical link between objects, people, and places.[4][5]

Palynomorphs

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Palynomorphs are broadly defined as the study of organic remains, includingmicrofossils,and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and range in size between 5 and 500micrometres.They are extracted from soils,sedimentary rocksandsediment cores,and other materials by a combination of physical (ultrasonic treatment andwet sieving) and chemical (acid digestion) procedures to remove the non-organic fraction. Palynomorphs may be composed of organic material such aschitin,pseudochitinandsporopollenin.[6]

Palynomorphs form ageologicalrecord of importance in determining the type ofprehistoric lifethat existed at the time the sedimentarystratawas laid down. As a result, these microfossils give important clues to the prevailingclimatic conditionsof the time. Their paleontological utility derives from an abundance numbering in millions of palynomorphs per gram in organic marine deposits, even when such deposits are generally notfossiliferous.Palynomorphs, however, generally have been destroyed inmetamorphicor recrystallized rocks.[6]

Typical palynomorphs includedinoflagellate cysts,acritarchs,spores,pollen,plant tissue,fungi,scolecodonts(scleroprotein teeth, jaws, and associated features ofpolychaeteannelidworms),arthropodorgans (such asinsectmouthparts), andchitinozoans.Palynomorph microscopic structures that are abundant in most sediments are resistant to routine pollen extraction.[6]

Palynofacies

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Apalynofaciesis the complete assemblage oforganic matterandpalynomorphsin a fossil deposit. The term was introduced by the FrenchgeologistAndré Combaz[wikidata]in 1964. Palynofacies studies are often linked to investigations of the organicgeochemistryofsedimentary rocks.The study of the palynofacies of asedimentary depositional environmentcan be used to learn about the depositional palaeoenvironments of sedimentary rocks in exploration geology, often in conjunction with palynological analysis andvitrinitereflectance.[7][8][9]

Palynofacies can be used in two ways:

  • Organicpalynofacies considers all the acid insolubleparticulate organic matter(POM), includingkerogenandpalynomorphsin sediments and palynological preparations of sedimentary rocks. The sieved or unsieved preparations may be examined usingstrew mountson microscope slides that may be examined using a transmitted light biological microscope orultraviolet(UV) fluorescence microscope. The abundance, composition and preservation of the various components, together with the thermal alteration of the organic matter is considered.
  • Palynomorph palynofacies considers the abundance, composition and diversity of palynomorphs in a sieved palynological preparation of sediments or palynological preparation ofsedimentary rocks.The ratio ofmarinefossilphytoplankton(acritarchsanddinoflagellatecysts), together withchitinozoans,to terrestrial palynomorphs (pollenandspores) can be used to derive a terrestrial input index in marine sediments.

History

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Pollen coresampling, Fort Bragg, North Carolina

Early history

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The earliest reported observations of pollen under a microscope are likely to have been in the 1640s by the EnglishbotanistNehemiah Grew,[10]who described pollen and the stamen, and concluded that pollen is required for sexual reproduction in flowering plants.

By the late 1870s, as optical microscopes improved and the principles ofstratigraphywere worked out,Robert KidstonandP. Reinschwere able to examine the presence of fossil spores in the Devonian and Carboniferous coal seams and make comparisons between the living spores and the ancient fossil spores.[11]Early investigators includeChristian Gottfried Ehrenberg(radiolarians,diatomsanddinoflagellate cysts),Gideon Mantell(desmids) andHenry Hopley White(dinoflagellate cysts).

1890s to 1940s

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Quantitative analysis of pollen began withLennart von Post's published work.[12]Although he published in the Swedish language, his methodology gained a wide audience through his lectures. In particular, hisKristianialecture of 1916 was important in gaining a wider audience.[13]Because the early investigations were published in the Nordic languages (Scandinavian languages), the field of pollen analysis was confined to those countries.[14]The isolation ended with the German publication ofGunnar Erdtman's 1921 thesis. The methodology of pollen analysis became widespread throughoutEuropeandNorth Americaand revolutionizedQuaternaryvegetation andclimate changeresearch.[13][15]

Earlier pollen researchers include Früh (1885),[16]who enumerated many common tree pollen types, and a considerable number ofsporesandherbpollen grains. There is a study of pollen samples taken from sediments of Swedish lakes by Trybom (1888);[17]pineandsprucepollen was found in such profusion that he considered them to be serviceable as "index fossils".Georg F. L. Sarauwstudied fossil pollen of middle Pleistocene age (Cromerian) from the harbour ofCopenhagen.[18]Lagerheim (in Witte 1905) and C. A.Weber (in H. A. Weber 1918) appear to be among the first to undertake 'percentage frequency' calculations.

1940s to 1989

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The termpalynologywas introduced by Hyde and Williams in 1944, following correspondence with the SwedishgeologistErnst Antevs,in the pages of thePollen Analysis Circular(one of the first journals devoted to pollen analysis, produced byPaul Searsin North America). Hyde and Williams chosepalynologyon the basis of theGreekwordspalunomeaning 'to sprinkle' andpalemeaning 'dust' (and thus similar to theLatinwordpollen).[19]The archive-based background to the adoption of the termpalynologyand to alternative names (e.g.paepalology,pollenology) has been exhaustively explored.[20]It has been argued there that the word gained general acceptance once used by the influential Swedish palynologistGunnar Erdtman.

Pollen analysis in North America stemmed fromPhyllis Draper,an MS student under Sears at the University of Oklahoma. During her time as a student, she developed the first pollen diagram from a sample that depicted the percentage of several species at different depths at Curtis Bog. This was the introduction of pollen analysis in North America;[21]pollen diagrams today still often remain in the same format with depth on the y-axis and abundances of species on the x-axis.

1990s to the 21st century

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Pollen analysis advanced rapidly in this period due to advances in optics and computers. Much of the science was revised byJohannes IversenandKnut Fægriin their textbook on the subject.[22]

Methods of studying palynomorphs

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Chemical preparation

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Chemical digestion follows a number of steps.[23]Initially the only chemical treatment used by researchers was treatment withpotassium hydroxide(KOH) to removehumicsubstances; defloculation was accomplished through surface treatment or ultra-sonic treatment, although sonification may cause the pollen exine to rupture.[14]In 1924, the use ofhydrofluoric acid(HF) to digestsilicatemineralswas introduced by Assarson and Granlund, greatly reducing the amount of time required to scan slides for palynomorphs.[24]

Palynological studies using peats presented a particular challenge because of the presence of well-preserved organic material, including fine rootlets, moss leaflets and organic litter. This was the last major challenge in the chemical preparation of materials for palynological study.Acetolysiswas developed by Gunnar Erdtman and his brother to remove these fine cellulose materials by dissolving them.[25]In acetolysis the specimen is treated withacetic anhydrideandsulfuric acid,dissolvingcellulisticmaterials and thus providing better visibility for palynomorphs.[26]

Some steps of the chemical treatments require special care for safety reasons, in particular the use of HF which diffuses very fast through the skin and, causes severe chemical burns, and can be fatal.[27]

Another treatment includes kerosene flotation forchitinousmaterials.

Analysis

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Once samples have been prepared chemically, they are mounted onmicroscopeslides using silicon oil, glycerol or glycerol-jelly and examined using lightmicroscopyor mounted on a stub forscanning electron microscopy.

Researchers will often study either modern samples from a number of unique sites within a given area, or samples from a single site with a record through time, such as samples obtained frompeator lake sediments. More recent studies have used the modern analog technique in which paleo-samples are compared to modern samples for which the parent vegetation is known.[28]

When the slides are observed under a microscope, the researcher counts the number of grains of each pollen taxon. This record is next used to produce apollen diagram.These data can be used to detectanthropogeniceffects, such as logging,[29]traditional patterns of land use[30]or long term changes in regional climate[31]

Applications

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Palynology can be applied to problems in many scientific disciplines includinggeology,botany,paleontology,archaeology,pedology (soil study),andphysical geography:

See also

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  • Aperture (botany)– Areas on the walls of a pollen grain, where the wall is thinner and/or softer
  • Aeroplankton– Tiny lifeforms floating and drifting in the air, carried by the wind

References

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  1. ^Gray, J.; Chaloner, W. G.; Westoll, T. S. (1985). "The Microfossil Record of Early Land Plants: Advances in Understanding of Early Terrestrialization, 1970–1984".Philosophical Transactions of the Royal Society B.309(1138): 167–195.Bibcode:1985RSPTB.309..167G.doi:10.1098/rstb.1985.0077.JSTOR2396358.
  2. ^Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds., 2005,Glossary of Geology(5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp.ISBN0-922152-76-4
  3. ^abcdWilliams, G., Fensome, R.A., Miller, M. and Bujak, J., 2020.Microfossils: palynology.In Sorkhabi, R., ed., 15 pp.,Encyclopedia of Petroleum Geoscience.Geneva, Switzerland, Springer Nature. 1000 pp.
  4. ^abcdKneller, M., and Fowell, F., 2009.Palynology.In Gornitz, V., ed., pp. 766-768.,Encyclopedia of Paleoclimatology and Ancient Environments.Geneva, Switzerland, Springer Dordrecht. 1049 pp.
  5. ^Laurence, A.R., and Bryant, V.M., 2009.Forensic Palynology.In Bruinsma, G., and Weisburd, D., ed., pp. 1471-1754.,Encyclopedia of Criminology and Criminal Justice.New York, New York, Springer Science+Business Media. 5632 pp.
  6. ^abcTraverse, A., 2007,Paleopalynology(2nd ed.). Amsterdam, the Netherlands, Springer-Dordrecht. 813 pp.ISBN978-1-4020-5609-3
  7. ^Fonseca, Carolina; Mendonça Filho, João Graciano; Lézin, Carine; de Oliveira, António Donizeti; Duarte, Luís V. (December 2019)."Organic matter deposition and paleoenvironmental implications across the Cenomanian-Turonian boundary of the Subalpine Basin (SE France): Local and global controls".International Journal of Coal Geology.218:103364.doi:10.1016/j.coal.2019.103364.
  8. ^Fonseca, Carolina; Mendonça Filho, João Graciano; Lézin, Carine; Duarte, Luís V.; Fauré, Phillipe (April 2018). "Organic facies variability during the Toarcian Oceanic Anoxic Event record of the Grands Causses and Quercy basins (southern France)".International Journal of Coal Geology.190:218–235.Bibcode:2018IJCG..190..218F.doi:10.1016/j.coal.2017.10.006.
  9. ^Fonseca, Carolina; Oliveira Mendonça, Joalice; Mendonça Filho, João Graciano; Lézin, Carine; Duarte, Luís V. (March 2018). "Thermal maturity assessment study of the late Pliensbachian-early Toarcian organic-rich sediments in southern France: Grands Causses, Quercy and Pyrenean basins".Marine and Petroleum Geology.91:338–349.Bibcode:2018MarPG..91..338F.doi:10.1016/j.marpetgeo.2018.01.017.
  10. ^Bradbury, S. (1967).The Evolution of the Microscope.New York: Pergamon Press. pp. 375 p.
  11. ^Jansonius, J.; D.C. McGregor (1996)."Introduction, Palynology: Principles and Applications".AASP Foundation.1:1–10. Archived fromthe originalon 2007-07-09.
  12. ^Traverse, Alfred and Sullivan, Herbert J. "The Background, Origin, and Early History of the American Association of Stratigraphic Palynologists" Palynology 7: 7-18 (1983)
  13. ^abFægri, Knut;Johs. Iversen(1964).Textbook of Pollen Analysis.Oxford:Blackwell Scientific Publications.Archived fromthe originalon 2010-04-03.
  14. ^abFaegri, Knut (1973). "In memoriam O. Gunnar E. Erdtman".Pollen et Spores.15:5–12.
  15. ^von Post, L (1918) "Skogsträdpollen i sydsvenska torvmosslagerföljder", Forhandlinger ved de Skandinaviske naturforskeres 16. møte i Kristiania 1916: p. 433
  16. ^Früh, J (1885) "Kritische Beiträge zur Kenntnis des Torfes", Jahrb.k.k.Geol.Reichsanstalt 35
  17. ^Trybom, F (1888) "Bottenprof fran svenska insjöar", Geol.Foren.Forhandl.10
  18. ^Sarauw, G. F. L. (1897)."Cromer-skovlaget i Frihavnen og trælevningerne i de ravførende sandlag ved København"[The Cromer Forest layer in the Free Harbour and Wood Remains in the Amber containing strata near Copenhagen](PDF).Meddelelser Fra Dansk Geologisk Forening / Bulletin of the Geological Society of Denmark(in Danish).1(4): 17–44.
  19. ^Hyde, H.A.; D.A. Williams (1944)."The Right Word".Pollen Analysis Circular.8:6. Archived fromthe originalon 2007-06-18.
  20. ^Edwards, Kevin J.; Pardoe, Heather S. (2018-01-02)."How palynology could have been paepalology: the naming of a discipline".Palynology.42(1): 4–19.Bibcode:2018Paly...42....4E.doi:10.1080/01916122.2017.1393020.hdl:2164/11661.ISSN0191-6122.
  21. ^Draper, P. (1928)."A demonstration of the technique of pollen analysis".Proceedings of the Oklahoma Academy of Science.8:63–64.
  22. ^Fægri, K. & Iversen, J. (1989)Textbook of pollen analysis.4th ed. John Wiley & Sons, Chichester. 328 p.
  23. ^Bennett, K.D.; Willis, K.J. (2001). "Pollen". In Smol, John P.; Birks, H. John B.; Last, William M. (eds.).Tracking Environmental Change Using Lake Sediments. Volume 3: Terrestrial, algal, and siliceous indicators.Dordrecht: Kluwer Academic Publishers. pp. 5–32.
  24. ^Assarson, G. och E.; Granlund, E. (1924). "En metod for pollenanalys av minerogena jordarter".Geologiska Föreningen i Stockholm Förhandlingar.46(1–2): 76–82.doi:10.1080/11035892409444879.
  25. ^Birks, H. J. B; Berglund, B. (2018). "One hundred years of Quaternary pollen analysis 1916–2016".Vegetation History and Archaeobotany.27(2): 271–390.Bibcode:2018VegHA..27..271B.doi:10.1007/s00334-017-0630-2.
  26. ^Erdtman, G. (1934). "Uber die Verwendung von Essigsaureanhydrid bei Pollenuntersuchungen".Sven. Bot. Tidskr.(in German).28:354–358.
  27. ^"Hydrofluoric acid fatality in Perth - hazard alert".1995-03-06.Retrieved2011-12-18.
  28. ^Overpeck, J. T.; T. Webb; I. C. Prentice (1985). "Quantitative interpretation of fossil pollen spectra: Dissimilarity coefficients and the method of modern analogs".Quaternary Research.23(1): 87–108.Bibcode:1985QuRes..23...87O.doi:10.1016/0033-5894(85)90074-2.S2CID129797797.
  29. ^ Niklasson, Mats; Matts Lindbladh; Leif Björkman (2002). "A long-term record ofQuercusdecline, logging and fires in a southern SwedishFagus-Piceaforest ".Journal of Vegetation Science.13(6): 765–774.Bibcode:2002JVegS..13..765N.doi:10.1111/j.1654-1103.2002.tb02106.x.JSTOR3236922.S2CID84934798.
  30. ^ Hebda, R.J.; R.W. Mathewes (1984). "Holocene history of cedar and native cultures on the North American Pacific Coast".Science.225(4663): 711–713.Bibcode:1984Sci...225..711H.doi:10.1126/science.225.4663.711.PMID17810290.S2CID39998080.
  31. ^Heusser, Calvin J.; L.E. Heusser; D.M. Peteet (1985). "Late-Quaternary climatic change on the American North Pacific coast".Nature.315(6019): 485–487.Bibcode:1985Natur.315..485H.doi:10.1038/315485a0.S2CID4345551.

Sources

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  • Moore, P.D., et al. (1991),Pollen Analysis(Second Edition). Blackwell Scientific Publications.ISBN0-632-02176-4
  • Traverse, A. (1988),Paleopalynology.Unwin Hyman.ISBN0-04-561001-0
  • Roberts, N. (1998),The Holocene an environmental history,Blackwell Publishing.ISBN0-631-18638-7
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