Ordovician Glaciation/Extinction Roundup
I found a bunch of new and new-ish work on the end-Ordovician extinction
- First plants cooled the Ordovician
- An asteroid impact origin of the Hirnantian (end-Ordovician) glaciation and mass extinction
- Late Ordovician mass extinction caused by volcanism, warming, and anoxia, not cooling and glaciation
- Late Ordovician climate change and extinctions driven by elevated volcanic nutrient supply
- A Cenozoic-style scenario for the end-Ordovician glaciation
- The Magnitude and Duration of Late Ordovician–Early Silurian Glaciation
- Large mass-independent sulphur isotope anomalies link stratospheric volcanism to the Late Ordovician mass extinction
- Mercury spikes suggest volcanic driver of the Ordovician-Silurian mass extinction
- Mercury in marine Ordovician/Silurian boundary sections of South China is sulfide-hosted and non-volcanic in origin
- Climate change and the selective signature of the Late Ordovician mass extinction
- Was the Late Ordovician mass extinction truly exceptional?
- An extraterrestrial trigger for the mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body
- An earth system approach to understanding the end-Ordovician (Hirnantian) mass extinction
- Did a gamma-ray burst initiate the late Ordovician mass extinction?
- Ordovician–Silurian true polar wander as a mechanism for severe glaciation and mass extinction
Commentary, with a large bibliography.
Now we’re up to at least 6 potential causes:
- Evolution and expansion of land plants
- Asteroid impact
- Large scale volcanism
- Dust from L-chondrite parent body breakup
- Gamma ray burst
- “True Polar Wander”
Three putative causes are extra-terrestrial. The “True Polar Wander” cause is just weird.
True Polar Wander:
true polar wander (TPW) is the movement of the entire solid Earth (mantle and crust) relative to Earth’s spin axis in order to stabilize Earth rotation.
Since this is paleontology, automatic gainsaying of every theory occurs: the mass extinction might not have been so massive, and maybe was quite short. Maybe there was large scale volcanism, and maybe there wasn’t. Maybe the oceans were cool, and maybe they weren’t.
I don’t know about you, but I intend to keep following this drama.