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

Carbon-14 (¹⁴C)

Answer

Uranium-Lead (U-Pb)

Answer

Rubidium-Strontium (Rb-Sr)

Question 2

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

Accepted Answer

Ordovician and Silurian

Answer

Devonian and Carboniferous

Answer

Jurassic and Cretaceous

Answer

Triassic and Permian

Question 3

The principle of faunal succession states that:

Accepted Answer

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

Answer

Older strata always contain more morphologically complex organisms

Answer

Marine fossils cannot occur in continental interior rock sequences

Answer

All fossils of the same species are found in identical stratigraphic positions globally

Question 4

A disconformity is a type of unconformity characterized by:

Accepted Answer

Missing strata between parallel beds with no angular discordance

Answer

Folded or tilted older beds overlain by flat-lying younger beds

Answer

Sedimentary rocks resting directly on igneous or metamorphic basement

Answer

A continuous and uninterrupted sequence of sedimentary strata

Question 5

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

Accepted Answer

Reptiles (including dinosaurs)

Answer

Fishes

Answer

Mammals

Answer

Marine invertebrates

Question 6

The Uranium-Lead (U-Pb) isotope system using zircon crystals is preferred for dating the oldest Earth rocks because:

Accepted Answer

Zircon incorporates uranium but rejects lead at crystallization, providing a reliable clock

Answer

Zircon has an extremely short half-life ideal for young rocks

Answer

Zircon is abundant in all sedimentary rock types

Answer

Lead does not diffuse out of zircon at any temperature

Question 7

Coccoliths are the calcite plates produced by which type of marine microorganism?

Accepted Answer

Coccolithophores (calcareous algae)

Answer

Diatoms (siliceous algae)

Answer

Foraminifera (calcareous protists)

Answer

Radiolaria (siliceous protists)