W3: L10 = Palaeontology [The Big 5 MEs] (Prof. Benoit) Flashcards
The Big 5 definitions? (3)
- ME 1.
- ME 2.
- Mathematical definition.
ME 1?
= a fast, global, non-selective (affects all types of environments) increase in extinction rate (>50% of genera, >10% of families) over a short period o f time.
ME 2?
= based on the fossil record of hard-shelled marine invertebrates & protozoans.
The Big 5 mathematical definition?
= a series of mass extinctions so severe they stand out over the average extinction rate (background extinction noise).
The Big 5 mathematical definition attribute?
Extinction level is above the 95% confidence level on the regression of extinction intensity over …
Aspects touched on The Big 5? (3)
- Division of geological stages.
- Main causes of MEs.
- List of the Big 5.
Division of geological stages attributes? (3)
- Geological stages are defined based on extinctions/extinction events.
- MEs mark the limits between the most important intervals of the Phanerozoic.
- Extinction events are a tool for geologists as it helps them date rocks.
Geological stages? (2)
- Periods.
- Eras.
Geological stages attributes? (3)
- Defined based on extinction events.
- Have its own homogenous fauna.
- Based on faunal turnover.
Most important intervals of the Phanerozoic (old to recent)? (3)
- Palaeozoic.
- Mesozoic.
- Cenozoic.
Palaeozoic animals? (2)
- Conodonts.
- Trilobites.
Mesozoic animals? (2)
- Dinosaurs.
- Ammonites.
Cenozoic animals?
Mammals.
Main causes of MEs (the usual suspects)? (5)
- Changes in O2 levels.
- Eustatic variations.
- Volcanic activity.
- Meteorite impacts.
- Spontaneous collapse of the ecosystem.
Changes in O2 levels attributes? (4)
- Greenhouse effect.
- Usually coincides with anoxia (lower O2).
- Anoxia caused by algae.
- CO2 & O2 participate in a constant feedback loop.
Eustatic variations?
= variations in sea levels.
Eustatic variations attributes? (2)
- Reduction of coastal habitats (predicted using rocks).
- Caused by continental drift.
Volcanic activity attributes? (3)?
- Trapps.
- Release poisonous gas, ashes & dust (causes global cooling).
- Release lots of CO2 (causes global warming).
Meteorite impacts attributes? (3)
- Sizeable meteorites can cause a nuclear winter, which then causes a global fire & collapse of the food chain.
- Nuclear winter is the main cause for ME.
- Not a major cause.
Spontaneous collapse of the ecosystem attribute?
With no particular reason.
List of the Big 5?
1) End-Ordovician.
2) End-Devonian.
3) End-Permian.
4) End-Triassic.
5) End-Cretaceous.
End-Ordovician is AKA?
Ordovician-Silurian extinction.
End-Ordovician extinction attributes? (7)
- The oldest one (therefore, most difficult to study).
- Documented in SA via the Cape Supergroup (contains soom shale).
- 445 Mya.
- 2nd most important ME.
- Possible causes (2).
- Why is it extremely debated?
- Opens up to the Devonian.
Why was the End-Ordovician extinction the 2nd most ME? (5)
- 60% of genera.
- 27% of families.
- 86% of species loss (estimated).
- Affected mostly trilobites, orthocerid (replaced by fish), brachiopods, bivalves, echinoderms & corals.
- No higher rank taxon becomes completely extinct.
Affected animals in End-Ordovician extinction? (6)
- Trilobites.
- Orchocerid.
- Brachiopods.
- Bivalves.
- Echinoderms.
- Corals.
Possible causes of End-Ordovician extinction? (2)
- Hirnantian glaciation.
- Supernova causing a gamma ray burst.
Hirnantian glaciation?
= global cooling causes marine regression & anoxia.
Why is the End-Ordovician extinction extremely debated? (2)
- Does not meet what a ME is.
- Lagged for 8-10 million years (took a lot of time to happen, therefore did not meet the “fast” criterion of an extinction event).
Opens up to the Devonian attributes? (3)
- Fish diversified into jawless fish, cartilaginous fish, ray-finned fish & lobe-finned fish.
- Armoured fish are currently extinct but flourished after the ME & was part of the post-extinction recovery.
- The 1st amphibians existed.
Devonian?
= Age of fish & 1st amphibians.
Fish diversified into:…? (4)
1) Jaw-less fish.
2) Cartilaginous fish.
3) Ray-finned fish.
4) Lobe-finned fish.
Jaw-less fish is AKA?
Agnatha.
Cartilaginous fish is AKA?
Chondrichthyes.
Ray-finned fish is AKA?
Actinopterygii.
Lobe-finned fish is AKA?
Sarcopterigii.
Egs of 1st amphibians? (2)
- Tutusias.
- Umzantsia from Witpoort Formation (SA).
Thing to note about the Causes of MEs (usual suspects)?
The causes are not mutually exclusive.
End-Devonian extinction attributes? (5)
- 365 Mya.
- Frasnian-Famenian boundary.
- 3rd most important ME.
- Possible causes (3).
- Opens up to the Carboniferous-Permian.
End-Devonian extinction is AKA?
Frasnian-Famenian extinction.
Why was the End-Devonian the 3rd most important ME? (6)
- 57% genera extinct.
- 20% families extinct.
- 75% species loss (estimated).
- Affected mostly coastal, reef-building species (corals & sponges).
- 95% vertebrates (fish) become extinct.
- Armoured fish are replaced by cartilaginous fish (sharks).
Possible causes? (3)
- 2 anoxic events (2 layers of black shales).
- Pangaea & orogenesis: global cooling, massive glaciation & droughts.
- Rise of trees: increased erosion of silica, storage of CO2 & then glaciation.
Carboniferous-Permian?
= Age of Karoo (reptiles).
Orogenesis?
= build up of mountains.