Paleontology and Geochronology Flashcards

Which radiometric dating method relies on the decay of uranium-238 to lead-206?

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.

The Cambrian Explosion is significant in paleontology because it marks:

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.

Which group of fossils serves as the best index fossils for Cretaceous marine sediments?

Answer: Ammonites

Ammonites were abundant, rapidly evolving, and widespread in Mesozoic seas, making them excellent index fossils for correlating Cretaceous marine strata globally.

The half-life of Carbon-14 (¹⁴C) used in radiocarbon dating is approximately:

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.

Which geologic era spans from approximately 252 to 66 million years ago?

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.

Biostratigraphy correlates and dates rock units primarily by using:

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.

The end-Permian (Permian-Triassic) mass extinction is estimated to have eliminated approximately what percentage of marine species?

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.