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Triassic-jurassic tetrapod extinctions: are they real?
Science (New York, N.Y.)
|September 2, 1977
Summary
Early Jurassic terrestrial vertebrate fossils from North America and Africa reveal new correlations. This finding challenges the idea of a major tetrapod extinction event at the Triassic-Jurassic boundary.
Area of Science:
- Paleontology
- Stratigraphy
- Vertebrate Evolution
Background:
- The Triassic-Jurassic boundary is traditionally considered a period of significant tetrapod extinction.
- Previous correlations of rock strata across continents have been used to define this boundary.
- The Newark Supergroup (eastern US), Glen Canyon Group (southwestern US), and Stormberg Group (southern Africa) are key fossil-bearing formations.
Purpose of the Study:
- To re-evaluate the age of key terrestrial vertebrate fossil assemblages from the Newark Supergroup, Glen Canyon Group, and Stormberg Group.
- To establish a more accurate chronostratigraphic correlation between these Southern Hemisphere and Northern Hemisphere formations.
- To test the hypothesis of a widespread tetrapod extinction event at the Triassic-Jurassic boundary.
Main Methods:
- Analysis of terrestrial vertebrate fossil occurrences within the specified geological groups.
- Biostratigraphic dating based on established fossil ranges.
- Correlation of geological strata across different continents using fossil evidence.
Main Results:
- Terrestrial vertebrate fossils indicate that parts of the Newark Supergroup and the entirety of the Glen Canyon Group are Early Jurassic in age.
- The Upper Stormberg Group of southern Africa is also confirmed as Early Jurassic.
- These findings establish a new chronostratigraphic framework for these rock units.
Conclusions:
- The previously inferred widespread tetrapod extinction at the Triassic-Jurassic boundary is an artifact of inaccurate correlation.
- The fossil record indicates a more gradual transition for terrestrial vertebrates across the Triassic-Jurassic boundary.
- This revised correlation provides a more robust understanding of vertebrate evolution during this critical period.
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