Introduction To Micro Fossil

Micropaleontology is the study of microscopic fossils. Because it is based only on fossil size, the term unites groups that are otherwise unrelated and includes microscopic organisms and microscopic parts of macroorganisms. Many sediments contain microfossils and they are important biostratigraphic, paleoenvironmental, and paleoceanographic indicators. Microfossils are important in biostratigraphy due to their abundance, global distribution, and durability. Their sensitivity to environmental conditions makes them useful in paleoenvironmen-tal reconstructions.

The groups considered in this chapter are listed in Table 13.1. Protists are single-celled eukaryotic organisms. They can be divided into autotrophic (self-nourishing, like plants) and het-erotrophic (consumers, like animals) organisms. Multicelled, but small, organisms are represented by ostracodes. Microscopic parts of macroorganisms covered are conodonts (tooth-like elements of vertebrates) and spores and pollen (the reproductive parts of plants).

Table 13.1 The microfossil groups covered in this chapter and their applications.

Main groups of microfossils Fossil Description Size Composition Habitat Range

Table 13.1 The microfossil groups covered in this chapter and their applications.

Main groups of microfossils Fossil Description Size Composition Habitat Range

Autotrophic protists

Acritarchs

Hollow vesicles, probably algal cysts

<100 Mm

Organic

Marine

Proterozoic to Recent

Dinoflagellates

Algae with organic-walled cysts

5-150 Mm

Organic

Aquatic

Silurian to Recent

Coccolithophores

Algae with spherical shells formed by platelets

<50 Mm

Calcite

Marine

Triassic to Recent

Diatoms

Algae contained within a frustule comprised

<200 Mm

Silica

Aquatic

Jurassic to Recent

of two elongate or circular valves

Heterotrophic protists

Radiolaria

Protists with a delicate exoskeleton in the

0.03-1.5 mm

Silica

Marine

Cambrian to Recent

form of spherical or conical mesh

Foraminifera

Testate protists with single-chambered,

0.01-100 mm

Organic

Marine

Cambrian to Recent

flask-like or complex, multichambered tests

Agglutinated

Calcareous

Microinvertebrates

Ostracodes

Crustacean arthropods with bivalved carapace

1-10 mm

Calcareous

Aquatic

Cambrian to Recent

Microvertebrates

Conodonts

Tooth-like elements of jawless vertebrate

0.1-5 mm

Phosphatic

Marine

Cambrian to Triassic

Plants

Spores

Resistant part of plant

5 Mm to 4 mm

Organic

Terrestrial

Devonian to Recent

Pollen

Resistant part of plant

5-200 Mm

Organic

Terrestrial

Devonian to Recent

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