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[[file:applied-paleontology_fig17-1.png|300px|thumb|{{figure number|1}}Typical calcareous foraminifera.]]

[[file:applied-paleontology_fig17-1.png|300px|thumb|{{figure number|1}}Typical calcareous foraminifera.]]

Calcareous foraminifera are a group of unicellular organisms (protists) that secrete a rigid calcite or aragonite shell (or test). Fossils of these forms are found in sediments of brackish to marine origin from Silurian to Holocene in age. Most are benthic (bottom dwelling), but a significant group in the late Mesozoic and Cenozoic are planktonic (floating) forms.

Calcareous foraminifera are a group of unicellular organisms (protists) that secrete a rigid calcite or aragonite shell (or test). Fossils of these forms are found in sediments of brackish to marine origin from Silurian to [[Holocene]] in age. Most are benthic (bottom dwelling), but a significant group in the late Mesozoic and [[Cenozoic]] are planktonic (floating) forms.

Some stratigraphically important foraminifera developed complex internal structures and, frequently, large test size. Studied primarily in thin section, these include the fusulinids (Pennsylvanian to Permian) and several groups of so-called larger foraminifera (Triassic to Holocene). They occur primarily in carbonate or fine-grained clastic rocks and are excellent time markers.

Some stratigraphically important foraminifera developed complex internal structures and, frequently, large test size. Studied primarily in thin section, these include the fusulinids (Pennsylvanian to Permian) and several groups of so-called larger foraminifera (Triassic to Holocene). They occur primarily in carbonate or fine-grained clastic rocks and are excellent time markers.

[[file:applied-paleontology_fig17-2.png|300px|thumb|{{figure number|2}}Typical ostracods.]]

[[file:applied-paleontology_fig17-2.png|300px|thumb|{{figure number|2}}Typical ostracods.]]

Ostracods are microscopic crustaceans whose fossils are found in Cambrian to Holocene rocks. They occur in most marine and nonmarine depositional environments and are generally excellent environmental indicators. The paleontologic application of ostracods is limited because (1) they are rare in many sections and (2) many species are endemic to local basins, so their age and environmental ranges are poorly understood. Ostracods typically have rapid evolutionary rates and are useful biostratigraphic tools in some situations:

Ostracods are microscopic crustaceans whose fossils are found in [[Cambrian]] to Holocene rocks. They occur in most marine and nonmarine depositional environments and are generally excellent environmental indicators. The paleontologic application of ostracods is limited because (1) they are rare in many sections and (2) many species are endemic to local basins, so their age and environmental ranges are poorly understood. Ostracods typically have rapid evolutionary rates and are useful biostratigraphic tools in some situations:

* In Paleozoic sequences

* In Paleozoic sequences

==See also==

==See also==

 

* [[Microfossils in exploration]]

* [[Microfossils in exploration]]

* [[Agglutinated microfossils]]

* [[Agglutinated microfossils]]

* [[Siliceous microfossils]]

* [[Siliceous microfossils]]

* [[Phosphatic microfossils]]

* [[Phosphatic microfossils]]

* [[Organic-walled microfossils]]

* [[Palynomorphs (organic-walled microfossils)]]

==External links==

==External links==

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Predicting the occurrence of oil and gas traps]]  

[[Category:Applied paleontology]]

[[Category:Applied paleontology]]