Micropaleontology
Encyclopedia
Micropaleontology is the branch of paleontology
that studies microfossils.
. 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 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 paleontologist
s, rather than micropaleontologists, but many micropaleontologists also study bryozoa.
In another example, many fossil 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 geological record, from the Precambrian
to the Holocene
. They are most common in deposits of marine
environments, but also occur in brackish water, fresh water and terrestrial sedimentary deposits. While every kingdom
of 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.
, as in coccolith
s and foraminifera
, (b) phosphatic
, as in the study of some vertebrate
s, (c) siliceous
, as in diatom
s and radiolaria, or (d) 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 taxonomic or ecological distinctions. Most researchers in this field
, known as micropaleontologists, are typically specialists in one or more taxonomic group
s.
Calcareous
[CaCO3] microfossils include Coccolith
s, Foraminifera
, Calcareous dinoflagellate
s, and Ostracod
s (seed shrimp).
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").
microfossils include Diatoms, Radiolarians, Silicoflagellate
s, Ebridian
s, phytolith
s, some scolecodonts
("worm" jaws), and Sponge spicule
s.
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.
, 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
analysis. A typical microfossil study will involve identification of a few hundred specimens from each of ten to a hundred samples.
. 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, as well as having near-global distribution, making biostratigraphic 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-organisms sinking from surface waters provide the dominant source of sediment, and they continuously accumulate (typically at rates of 20-50 million per 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 determining the provenance of archaeological artefacts.
Micropaleontology is also a tool of Geoarchaeology
used in archaeological reconstruction of human habitation sites and environments. Changes in the microfossil population abundance in the stratigraphy of current and former water bodies reflect changes in environmental conditions. Naturally occurring Ostracods in freshwater bodies are impacted by changes in salinity and pH due to human activities. When correlated with other dating techniques, prehistoric environments can be reconstructed. Work on Lake Tanganyika
provided a profile of human induced environmental changes of a 4,000 year period.
Similar work in the arid American Southwest has provided information on irrigation canals used by prehistoric peoples from 2100 B.C. to 500 B.C. Other archaeological work in arid climates throughout the Americas has incorporated Micropaleontological analysis to build a more complete picture of prehistoric climate and human activity.
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
that studies microfossils.
Microfossils
Microfossils are fossils generally not larger than four millimeters, and commonly smaller than one millimeter, the study of which requires the use of light or electron microscopyMicroscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
. Fossils which can be studied with the naked eye or low-powered magnification, such as a hand lens, are referred to as macrofossil
Macrofossil
Macrofossils are preserved organic remains large enough to be visible without a microscope. Most fossils discussed in the article Fossil are macrofossils.-Macrofossil contrasted with Microfossil:...
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
Bryozoa
The Bryozoa, also known as Ectoprocta or commonly as moss animals, are a phylum of aquatic invertebrate animals. Typically about long, they are filter feeders that sieve food particles out of the water using a retractable lophophore, a "crown" of tentacles lined with cilia...
(especially the Cheilostomata
Cheilostomata
Cheilostomata, an order of Bryozoa in the class Gymnolaemata, are exclusively marine, colonial invertebrate animals. Cheilostome colonies are composed of calcium carbonate and grow on a variety of surfaces, including rocks, shells, seagrass and kelps. The colony shapes range from simple encrusting...
) have relatively large colonies
Colony (biology)
In biology, a colony reference to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defense or the ability to attack bigger prey. Some insects live only in 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 paleontologist
Invertebrate paleontology
Invertebrate paleontology is sometimes described as Invertebrate paleozoology or Invertebrate paleobiology....
s, rather than micropaleontologists, but many micropaleontologists also study bryozoa.
In another example, many fossil genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of Foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
, 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 geological record, from the Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
to the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
. They are most common in deposits of marine
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...
environments, but also occur in brackish water, fresh water and terrestrial sedimentary deposits. While every kingdom
Kingdom (biology)
In biology, kingdom is a taxonomic rank, which is either the highest rank or in the more recent three-domain system, the rank below domain. Kingdoms are divided into smaller groups called phyla or divisions in botany...
of life is represented in the microfossil record, the most abundant forms are protist
Protist
Protists are a diverse group of eukaryotic microorganisms. Historically, protists were treated as the kingdom Protista, which includes mostly unicellular organisms that do not fit into the other kingdoms, but this group is contested in modern taxonomy...
skeletons or cysts from the Chrysophyta
Chrysophyta
Chrysophyta is a term used to refer to certain heterokonts.It can be used to refer to:* golden algae* golden algae and diatoms together....
, Pyrrhophyta, Sarcodina, acritarch
Acritarch
Acritarchs are small organic fossils, present from approximately to the present. Their diversity reflects major ecological events such as the appearance of predation and the Cambrian explosion.-Definition:In general, any small, non-acid soluble Acritarchs are small organic fossils, present from...
s and chitinozoa
Chitinozoa
Chitinozoa are a taxon of flask-shaped, organic walled marine microfossils produced by an as yet unknown animal. Common from the Ordovician to Devonian periods , the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe...
ns, together with pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
and spores from the vascular plant
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s.
Areas of study
Micropaleontology can be roughly divided into four areas of study on the basis of microfossil composition: (a) calcareousCalcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
, as in coccolith
Coccolith
Coccoliths are individual plates of calcium carbonate formed by coccolithophores which are arranged around them in a coccosphere.- Formation and composition :...
s and foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
, (b) phosphatic
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, as in the study of some vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
s, (c) siliceous
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
, as in diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s and radiolaria, or (d) organic
Organic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
, as in the pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
and spores studied in palynology
Palynology
Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...
.
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 taxonomic or ecological distinctions. Most researchers in this field
Field research
Field research is the collection of raw data in natural settings. It helps to reveal the habits and habitats of various organisms present in their natural surroundings...
, known as micropaleontologists, are typically specialists in one or more taxonomic group
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...
s.
Calcareous microfossils
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
[CaCO3] microfossils include Coccolith
Coccolith
Coccoliths are individual plates of calcium carbonate formed by coccolithophores which are arranged around them in a coccosphere.- Formation and composition :...
s, Foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
, Calcareous dinoflagellate
Dinoflagellate
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...
s, and Ostracod
Ostracod
Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....
s (seed shrimp).
Phosphatic microfossils
PhosphaticPhosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
microfossils include Conodont
Conodont
Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. Knowledge about soft tissues remains relatively sparse to this day...
s (tiny oral structures of an extinct chordate group), some scolecodonts
Scolecodonts
A scolecodont is the jaw of a polychaete annelid, a common type of fossil-producing segmented worm useful in invertebrate paleontology. Scolecodonts are common and diverse microfossils, which range from the Cambrian period to the present...
("worm" jaws), Shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
spines and teeth, and other Fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
remains (collectively called "ichthyolith
Ichthyolith
An ichthyolith is any disarticulated remains of a fish found in the fossil record, most often a scale, denticle or tooth....
s").
Siliceous microfossils
SiliceousSilicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
microfossils include Diatoms, Radiolarians, Silicoflagellate
Silicoflagellate
Dictyochales are a small group of unicellular heterokont algae, found in marine environments.-Characteristics:In one stage of their life cycle, they produce a siliceous skeleton, composed of a network of bars and spikes arranged to form an internal basket...
s, Ebridian
Ebriid
The Ebridea is a group of phagotrophic flagellate protist present in marine coastal plankton communities worldwide. Ebria tripartita is one of two described extant species in the Ebridea....
s, phytolith
Phytolith
Some plants can take up silica in the soil, whereupon it is deposited within different intracellular and extracellular structures of the plant. After these plants decay, silica is redeposited in the soil in the form of phytoliths , which are rigid, microscopic structures of varying sizes and shapes...
s, some scolecodonts
Scolecodonts
A scolecodont is the jaw of a polychaete annelid, a common type of fossil-producing segmented worm useful in invertebrate paleontology. Scolecodonts are common and diverse microfossils, which range from the Cambrian period to the present...
("worm" jaws), and Sponge spicule
Sponge spicule
Spicules are structural elements found in most sponges. They provide structural support and deter predators. Large spicules, visible to the naked eye are referred to as megascleres, while smaller, microscopic ones are termed microscleres.- Structure :...
s.
Organic microfossils
The study of organicOrganic matter
Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...
microfossils is called palynology
Palynology
Palynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...
. Organic microfossils include pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
, spores, Chitinozoa
Chitinozoa
Chitinozoa are a taxon of flask-shaped, organic walled marine microfossils produced by an as yet unknown animal. Common from the Ordovician to Devonian periods , the millimetre-scale organisms are abundant in almost all types of marine sediment across the globe...
ns (thought to be the egg cases of marine invertebrates), Scolecodonts
Scolecodonts
A scolecodont is the jaw of a polychaete annelid, a common type of fossil-producing segmented worm useful in invertebrate paleontology. Scolecodonts are common and diverse microfossils, which range from the Cambrian period to the present...
("worm" jaws), Acritarchs, Dinoflagellate
Dinoflagellate
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...
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 centrifugeCentrifuge
A centrifuge is a piece of equipment, generally driven by an electric motor , that puts an object in rotation around a fixed axis, applying a force perpendicular to the axis...
, 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
Multivariate statistics
Multivariate statistics is a form of statistics encompassing the simultaneous observation and analysis of more than one statistical variable. The application of multivariate statistics is multivariate analysis...
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 biostratigraphyBiostratigraphy
Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them. Usually the aim is correlation, demonstrating that a particular horizon in one geological section represents the same period...
. 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
Facies
In geology, facies are a body of rock with specified characteristics. Ideally, a facies is a distinctive rock unit that forms under certain conditions of sedimentation, reflecting a particular process or environment....
or paleoenvironments, as well as having near-global distribution, making biostratigraphic 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-organisms sinking from surface waters provide the dominant source of sediment, and they continuously accumulate (typically at rates of 20-50 million per 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
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
-body dating and for paleoenvironmental reconstruction – heavily used in both petroleum
Petroleum
Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
and paleoceanography
Paleoceanography
Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation.- Source of information :...
– micropaleontology has also found a number of less orthodox applications, such as its growing role in forensic police investigation or in determining the provenance of archaeological artefacts.
Micropaleontology is also a tool of Geoarchaeology
Geoarchaeology
Geoarchaeology is a multi-disciplinary approach which uses the techniques and subject matter of geography, geology and other Earth sciences to examine topics which inform archaeological knowledge and thought...
used in archaeological reconstruction of human habitation sites and environments. Changes in the microfossil population abundance in the stratigraphy of current and former water bodies reflect changes in environmental conditions. Naturally occurring Ostracods in freshwater bodies are impacted by changes in salinity and pH due to human activities. When correlated with other dating techniques, prehistoric environments can be reconstructed. Work on Lake Tanganyika
Lake Tanganyika
Lake Tanganyika is an African Great Lake. It is estimated to be the second largest freshwater lake in the world by volume, and the second deepest, after Lake Baikal in Siberia; it is also the world's longest freshwater lake...
provided a profile of human induced environmental changes of a 4,000 year period.
Similar work in the arid American Southwest has provided information on irrigation canals used by prehistoric peoples from 2100 B.C. to 500 B.C. Other archaeological work in arid climates throughout the Americas has incorporated Micropaleontological analysis to build a more complete picture of prehistoric climate and human activity.
External links
- The Micropalaeontological Society
- Centre for Palynology, University of Sheffield, UK
- The American Association of Stratigraphic Palynologists (AASP)
- Commission Internationale de Microflore du Paléozoique (CIMP), international commission for Palaeozoic palynology.
- The International Nannoplankton Association
- CIMP Subcommission on Acritarchs
- CIMP Chitinozoan Subcommission
- Micropaleontology Press, a division of the Micropaleontology Project, a nonprofit organization with the mission of promoting the science of micropaleontology.
- University of California, Berkeley, microfossil collections.
- The Ocean Drilling Programme (ODP) Micropaleontological reference centres.
- University College, London, Micropalaeontology Unit, including the MIRACLE microfossil image database.
- 2500+ images of Foraminifera with a searchable database