ASBOG Paleontology and Geochronology 1 — Questions and Answers
Question 1: Which radiometric dating method relies on the decay of uranium-238 to lead-206?
- Carbon-14 dating
- Potassium-Argon dating
- Uranium-Lead dating (Correct answer)
- Rubidium-Strontium dating
Correct answer: Uranium-Lead dating
Uranium-Lead (U-Pb) dating uses the decay of ²³⁸U to ²⁰⁶Pb (half-life ~4.47 billion years), making it suitable for dating very old rocks and zircon minerals.
Question 2: The Cambrian Explosion is significant in paleontology because it marks:
- The first appearance of vascular land plants
- The mass extinction of the dinosaurs
- The rapid diversification of complex multicellular animal body plans (Correct answer)
- The formation of extensive coal-forming swamp forests
Correct answer: The rapid diversification of complex multicellular animal body plans
The Cambrian Explosion (~541 Ma) records the geologically rapid appearance of most major animal phyla, with diverse hard-shelled organisms appearing in the fossil record for the first time.
Question 3: Which group of fossils serves as the best index fossils for Cretaceous marine sediments?
- Trilobites
- Ammonites (Correct answer)
- Graptolites
- Fusulinids
Correct answer: Ammonites
Ammonites were abundant, rapidly evolving, and widespread in Mesozoic seas, making them excellent index fossils for correlating Cretaceous marine strata globally.
Question 4: The half-life of Carbon-14 (¹⁴C) used in radiocarbon dating is approximately:
- 704 million years
- 1.25 billion years
- 5,730 years (Correct answer)
- 48.8 billion years
Correct answer: 5,730 years
¹⁴C has a half-life of ~5,730 years, limiting its effective dating range to materials younger than ~50,000 years before atmospheric ¹⁴C becomes undetectable.
Question 5: Which geologic era spans from approximately 252 to 66 million years ago?
- Paleozoic Era
- Cenozoic Era
- Proterozoic Eon
- Mesozoic Era (Correct answer)
Correct answer: Mesozoic Era
The Mesozoic Era (252–66 Ma) is bounded by the Permian-Triassic extinction at its base and the Cretaceous-Paleogene extinction at its top, and encompasses the Triassic, Jurassic, and Cretaceous periods.
Question 6: Biostratigraphy correlates and dates rock units primarily by using:
- Geomagnetic polarity reversals
- Seismic wave velocities
- Fossil assemblages and their stratigraphic ranges (Correct answer)
- Absolute radiometric ages
Correct answer: Fossil assemblages and their stratigraphic ranges
Biostratigraphy establishes time-equivalent rock units (biozones) by tracking the first and last appearances of fossil taxa, allowing correlation across geographic distances.
Question 7: The end-Permian (Permian-Triassic) mass extinction is estimated to have eliminated approximately what percentage of marine species?
- 30%
- 50%
- 70%
- 96% (Correct answer)
Correct answer: 96%
The Permian-Triassic extinction (~252 Ma) was the most severe in Earth history, eliminating an estimated 96% of marine species and 70% of terrestrial vertebrate species.
ASBOG Paleontology and Geochronology 1
Which radiometric dating method relies on the decay of uranium-238 to lead-206?