Micropalaeontology Questions and Answers

Q: Which of the following microfossils is commonly used in biostratigraphic correlation of Palaeozoic marine strata ?

The answer is Chitinozoans.Chitinozoans are flask-shaped, organic-walled marine microfossils of uncertain affinity that lived only from the Ordovician to the Devonian. They evolved quickly, are abundant in marine shales and resist acid processing, so they are a standard tool for zoning and correlating Lower Palaeozoic marine strata.The other groups are too young. Angiosperm pollen appears only in the Early Cretaceous, and is a land-plant fossil in any case. Diatoms are known from the Jurassic and become common in the Cretaceous and Cenozoic. Dinoflagellate cysts are important from the Triassic onwards, so all three are Mesozoic-Cenozoic tools.

Q: The chemical composition of the planktic foraminifera's shell/test is :

The test of planktic foraminifera is made of \(\mathrm{CaCO_{3}}\), calcium carbonate.Planktic foraminifera such as Globigerina build their chambered tests from calcite. Their accumulation on the seafloor forms globigerina ooze, and the oxygen and carbon isotopes in their calcite are a key archive of past ocean temperature and ice volume.Silica (SiO2) forms the skeletons of radiolarians and diatoms, not foraminifera. Magnesium sulphate and calcium phosphate are not used by foraminifera; phosphate builds vertebrate bone and the shells of some inarticulate brachiopods.

Q: Which foraminifera is used as an index fossil for the Eocene and Oligocene ?

The Eocene-Oligocene index foraminifer is Lepidocycilina (Lepidocyclina).Lepidocyclina is a large benthic foraminifer that appeared in the late Middle to Late Eocene and flourished through the Oligocene into the Miocene, making it a standard index fossil for those carbonate successions, including those of western India.Miogypsinids range from the Oligocene into the Miocene and are used mainly for the Miocene, Globotruncanella is a Late Cretaceous planktic form, and fusulinids are Carboniferous to Permian, so none of them indexes the Eocene and Oligocene.

Which of the following microfossils is commonly used in biostratigraphic correlation of Palaeozoic marine strata ?

A.Angiosperm Pollen
B.Diatoms
C.Chitinozoans
D.Dinoflagellates

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: C

The answer is Chitinozoans.

Chitinozoans are flask-shaped, organic-walled marine microfossils of uncertain affinity that lived only from the Ordovician to the Devonian. They evolved quickly, are abundant in marine shales and resist acid processing, so they are a standard tool for zoning and correlating Lower Palaeozoic marine strata.

The other groups are too young. Angiosperm pollen appears only in the Early Cretaceous, and is a land-plant fossil in any case. Diatoms are known from the Jurassic and become common in the Cretaceous and Cenozoic. Dinoflagellate cysts are important from the Triassic onwards, so all three are Mesozoic-Cenozoic tools.

Discuss in Forum

The chemical composition of the planktic foraminifera's shell/test is :

A.\(\mathrm{CaCO_{3}}\)
B.\(\mathrm{MgSO_{4}}\)
C.\(\mathrm{SiO_{2}}\)
D.\(\mathrm{Ca_{3}(PO)_{4}}\)

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: A

The test of planktic foraminifera is made of \(\mathrm{CaCO_{3}}\), calcium carbonate.

Planktic foraminifera such as Globigerina build their chambered tests from calcite. Their accumulation on the seafloor forms globigerina ooze, and the oxygen and carbon isotopes in their calcite are a key archive of past ocean temperature and ice volume.

Silica (SiO₂) forms the skeletons of radiolarians and diatoms, not foraminifera. Magnesium sulphate and calcium phosphate are not used by foraminifera; phosphate builds vertebrate bone and the shells of some inarticulate brachiopods.

Discuss in Forum

Which foraminifera is used as an index fossil for the Eocene and Oligocene ?

A.Miogypinid
B.Globotruncanella
C.Lepidocycilina
D.Fusulinid

Exam Year(s)

MH SET - 2024, SET Exam - 2024,

Answer: C

The Eocene-Oligocene index foraminifer is Lepidocycilina (Lepidocyclina).

Lepidocyclina is a large benthic foraminifer that appeared in the late Middle to Late Eocene and flourished through the Oligocene into the Miocene, making it a standard index fossil for those carbonate successions, including those of western India.

Miogypsinids range from the Oligocene into the Miocene and are used mainly for the Miocene, Globotruncanella is a Late Cretaceous planktic form, and fusulinids are Carboniferous to Permian, so none of them indexes the Eocene and Oligocene.

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