ASBOG Paleontology and Geochronology 2

Question 1

Which radiometric dating method is most appropriate for dating volcanic rocks that are 1–10 million years old?

Accepted Answer

Potassium-Argon (K-Ar)

Answer

Potassium-Argon dating (half-life of ⁴⁰K = 1.25 Ga) is well-suited for volcanic rocks in the 1–10 Ma range because argon gas is completely lost when lavas erupt, resetting the clock.

Question 2

Graptolites are most useful as index fossils for which geologic periods?

Accepted Answer

Ordovician and Silurian

Answer

Graptolites (colonial hemichordates) were abundant planktonic organisms from the Cambrian through Carboniferous, but are most widely used as zone fossils for Ordovician and Silurian correlations.

Question 3

The principle of faunal succession states that:

Accepted Answer

Fossil assemblages succeed one another vertically in a definite and determinable order

Answer

William Smith's principle of faunal succession establishes that different strata contain different characteristic fossil assemblages, and these assemblages appear in a consistent vertical sequence that can be recognized worldwide.

Question 4

A disconformity is a type of unconformity characterized by:

Accepted Answer

Missing strata between parallel beds with no angular discordance

Answer

A disconformity occurs where parallel sedimentary layers are separated by a surface of erosion or non-deposition, representing a time gap without angular discordance between the units.

Question 5

The Mesozoic Era is commonly referred to as the 'Age of' which organisms?

Accepted Answer

Reptiles (including dinosaurs)

Answer

The Mesozoic Era is called the 'Age of Reptiles' because dinosaurs, marine reptiles (plesiosaurs, mosasaurs), pterosaurs, and other reptilian groups dominated terrestrial and marine ecosystems.

ASBOG - Association of State Boards of Geology Practice Test

ASBOG - Association of State Boards of Geology Practice Test

ASBOG Paleontology and Geochronology 2