Palynology is the study of microorganisms and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and occur in , , and even some metasedimentary rocks. Palynomorphs are the microscopic, acid-resistant organic remains and debris produced by a wide variety of , , and Protista that have existed since the late Proterozoic.[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. ]
It is the science that studies contemporary and fossil palynomorphs (paleopalynology), including pollen, spores, , dinocysts, acritarchs, and Scolecodonts, together with particulate organic matter (POM) and kerogen found in sedimentary rocks and . Palynology does not include diatoms, foraminiferans or other organisms with siliceous or calcareous tests. The name of the science and organisms is derived from the Greek , "strew, sprinkle" and -logy) or of "particles that are strewn".[Williams, 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.][Kneller, 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.]
Palynology is an interdisciplinary science that stands at the intersection of earth science (geology or geological science) and biological science (biology), particularly plant science (botany). Biostratigraphy, a branch of paleontology and paleobotany, involves fossil palynomorphs from the Precambrian to the Holocene for their usefulness in the relative dating and correlation of sedimentary strata. Palynology is also used to date and understand the evolution of many kinds of plants and animals. In paleoclimatology, fossil palynomorphs are studied for their usefulness in understanding ancient Earth history in terms of reconstructing paleoecology and paleoclimates.
Palynology is quite useful in disciplines such as archeology, in honey production, and Criminal law and civil law.[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.]
Palynomorphs
Palynomorphs are broadly defined as organic remains, including
, and microscopic fragments of mega-organisms that are composed of acid-resistant organic material and range in size between 5 and 500
. They are extracted from soils,
and
pollen core, and other materials by a combination of physical (ultrasonic treatment and
sieve analysis) and chemical (acid digestion) procedures to remove the non-organic fraction. Palynomorphs may be composed of organic material such as
chitin,
pseudochitin and
sporopollenin.
[Traverse, A., 2007, Paleopalynology (2nd ed.). Amsterdam, the Netherlands, Springer-Dordrecht. 813 pp. ]
Palynomorphs form a geological record of importance in determining the type of prehistoric life that existed at the time the sedimentary strata was laid down. As a result, these microfossils give important clues to the prevailing paleogeography of 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 not fossiliferous. Palynomorphs, however, generally have been destroyed in Metamorphic rock or recrystallized rocks.
Typical palynomorphs include dinoflagellate cysts, , , pollen, plant tissue, fungi, scolecodonts (scleroprotein teeth, jaws, and associated features of polychaeta annelid worms), arthropod organs (such as insect mouthparts), and . Palynomorph microscopic structures that are abundant in most sediments are resistant to routine pollen extraction.
Palynofacies
A
palynofacies is the complete assemblage of
organic matter and palynomorphs in a fossil deposit. The term was introduced by the French
geologist in 1964. Palynofacies studies are often linked to investigations of the organic
geochemistry of
. The study of the palynofacies of a sedimentary depositional environment can be used to learn about the depositional palaeoenvironments of sedimentary rocks in exploration geology, often in conjunction with palynological analysis and
vitrinite reflectance.
Palynofacies can be used in two ways:
-
Organic matter palynofacies considers all the acid insoluble particulate organic matter (POM), including kerogen and palynomorphs in sediments and palynological preparations of sedimentary rocks. The sieved or unsieved preparations may be examined using on microscope slides that may be examined using a transmitted light biological microscope or ultraviolet (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 of . The ratio of ocean fossil phytoplankton (acritarchs and dinoflagellate cysts), together with , to terrestrial palynomorphs (pollen and spores) can be used to derive a terrestrial input index in marine sediments.
History
Early history
The earliest reported observations of pollen under a microscope are likely to have been in the 1640s by the English
botanist Nehemiah Grew,
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 of stratigraphy were worked out, Robert Kidston and P. Reinsch were 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.
1890s to 1940s
Quantitative analysis of pollen began with Lennart von Post's published work.
[Traverse, Alfred and Sullivan, Herbert J. "The Background, Origin, and Early History of the American Association of Stratigraphic Palynologists" Palynology 7: 7-18 (1983)] Although he published in the Swedish language, his methodology gained a wide audience through his lectures. In particular, his
Kristiania lecture of 1916 was important in gaining a wider audience.
Because the early investigations were published in the Nordic languages (Scandinavian languages), the field of pollen analysis was confined to those countries.
The isolation ended with the German publication of
Gunnar Erdtman's 1921 thesis. The methodology of pollen analysis became widespread throughout
Europe and
North America and revolutionized
Quaternary vegetation and climate change research.
[von Post, L (1918) "Skogsträdpollen i sydsvenska torvmosslagerföljder", Forhandlinger ved de Skandinaviske naturforskeres 16. møte i Kristiania 1916: p. 433]
Earlier pollen researchers include Früh (1885),[Früh, J (1885) "Kritische Beiträge zur Kenntnis des Torfes", Jahrb.k.k.Geol.Reichsanstalt 35] who enumerated many common tree pollen types, and a considerable number of and herb pollen grains. There is a study of pollen samples taken from sediments of Swedish lakes by Trybom (1888);[Trybom, F (1888) "Bottenprof fran svenska insjöar", Geol.Foren.Forhandl.10] Pinus and Picea pollen was found in such profusion that he considered them to be serviceable as "index fossils". Georg F. L. Sarauw studied fossil pollen of middle Pleistocene age (Cromerian) from the harbour of Copenhagen.
1940s to 1989
The term
palynology was introduced by Hyde and Williams in 1944, following correspondence with the Swedish
geologist Ernst Antevs, in the pages of the
Pollen Analysis Circular (one of the first journals devoted to pollen analysis, produced by
Paul Sears in North America). Hyde and Williams chose
palynology on the basis of the
Ancient Greek words
paluno meaning 'to sprinkle' and
pale meaning 'dust' (and thus similar to the
Latin word
pollen).
The archive-based background to the adoption of the term
palynology and to alternative names (e.g.
paepalology,
pollenology) has been exhaustively explored.
It has been argued there that the word gained general acceptance once used by the influential Swedish palynologist
Gunnar Erdtman.
Pollen analysis in North America stemmed from Phyllis 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;
1990s to the 21st century
Pollen analysis advanced rapidly in this period due to advances in optics and computers. Much of the science was revised by
Johannes Iversen and Knut Fægri in their textbook on the subject.
[Fægri, K. & Iversen, J. (1989) Textbook of pollen analysis. 4th ed. John Wiley & Sons, Chichester. 328 p.]
Methods of studying palynomorphs
Chemical preparation
Chemical digestion follows a number of steps.
[
] Initially the only chemical treatment used by researchers was treatment with potassium hydroxide (KOH) to remove
Humic acid substances; defloculation was accomplished through surface treatment or ultra-sonic treatment, although sonification may cause the pollen exine to rupture.
In 1924, the use of hydrofluoric acid (HF) to digest
silicate was introduced by Assarson and Granlund, greatly reducing the amount of time required to scan slides for palynomorphs.
[
]
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. Acetolysis was developed by Gunnar Erdtman and his brother to remove these fine cellulose materials by dissolving them.
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.[
]
Another treatment includes kerosene flotation for materials.
Analysis
Once samples have been prepared chemically, they are mounted on
microscope slides using silicon oil, glycerol or glycerol-jelly and examined using light
microscopy or mounted on a stub for scanning 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 from peat or 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.
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 a pollen diagram. These data can be used to detect anthropogenic effects, such as logging,[
] traditional patterns of land use[
] or long term changes in regional climate
Applications
Palynology can be applied to problems in many scientific disciplines including
geology,
botany,
paleontology,
archaeology, pedology (soil study), and physical geography:
-
Biostratigraphy and geochronology. Geologists use palynological studies in biostratigraphy to correlate stratum and determine the relative age of a given bed, horizon, formation or stratigraphy sequence. Because the distribution of acritarchs, , dinoflagellate cysts, pollen and provides evidence of stratigraphy through biostratigraphy and palaeoenvironmental reconstruction, one common and lucrative application of palynology is in petroleum and Natural gas exploration.
-
Paleoecology and climate change. Palynology can be used to reconstruct past vegetation (land plants) and ocean and Freshwater phytoplankton communities, and so infer past environmental (paleoenvironment) and paleoclimatology conditions in an area thousands or millions of years ago, a fundamental part of research into climate change.
-
Organic palynofacies studies, which examine the preservation of the particulate organic matter and palynomorphs provides information on the depositional environment of sediments and depositional palaeoenvironments of sedimentary.
-
Geothermal alteration studies examine the color of palynomorphs extracted from rocks to give the thermal alteration and hydrocarbon of sedimentary sequences, which provides estimates of maximum palaeotemperatures.
-
Limnology studies. Freshwater palynomorphs and animal and plant fragments, including the and () can be used to study past lake levels and long term climate change.
-
Taxonomy and evolution. Involving the use of pollen morphological characters as source of taxonomic data to delimit plant species under same family or genus. Pollen apertural status is frequently used for differential sorting or finding similarities between species of the same taxa. This is also called Palynotaxonomy.
-
Forensic palynology: the study of pollen and other palynomorphs for evidence at a crime scene.
-
Allergy studies and pollen counting. Studies of the geographic distribution and seasonal production of pollen, can be used to forecast pollen conditions, helping sufferers of allergies such as hay fever.
-
Melissopalynology: the study of pollen and spores found in honey.
-
Archaeological palynology examines human uses of plants in the past. This can help determine seasonality of site occupation, presence or absence of agricultural practices or products, and 'plant-related activity areas' within an archaeological context. Bonfire Shelter is one such example of this application.
See also
Sources
-
Moore, P.D., et al. (1991), Pollen Analysis (Second Edition). Blackwell Scientific Publications.
-
Traverse, A. (1988), Paleopalynology. Unwin Hyman.
-
Roberts, N. (1998), The Holocene an environmental history, Blackwell Publishing.
External links
-
The AASP - The Palynological Society
-
International Federation of Palynological Societies
-
Palynology Laboratory, French Institute of Pondicherry, India
-
The Palynology Unit, Kew Gardens, UK
-
PalDat, palynological database hosted by the University of Vienna, Austria
-
The Micropalaeontological Society
-
Commission Internationale de Microflore du Paléozoique (CIMP), International Commission for Palaeozoic Palynology
-
Centre for Palynology, University of Sheffield, UK
-
Linnean Society Palynology Specialist Group (LSPSG)
-
Canadian Association of Palynologists
-
Pollen and Spore Identification Literature
-
Palynologische Kring, The Netherlands and Belgium
-
Palynofacies, an annotated link directory.
-
Acosta et al., 2018. Climate change and peopling of the Neotropics during the Pleistocene-Holocene transition. Boletín de la Sociedad Geológica Mexicana. http://boletinsgm.igeolcu.unam.mx/bsgm/index.php/component/content/article/368-sitio/articulos/cuarta-epoca/7001/1857-7001-1-Acosta
