Historical Geology - The end-Cretaceous Extinction Event

Question 1

What happens in the end-Cretaceous Extinction Event (K/Pg) for plants?

Answer 1

• major extinction at the species level

- no major families go extinct

Question 2

What happens in the end-Cretaceous Extinction event (K/Pg) for marine invertebrate?

Answer 2

• all large ammonoids and belemnites
• All plesiosaurs and mosasaurs
• Rudist and inoceramid bivalves
• > 60% of scleractinian corals
• Relatively few bony fish or chondrichthyans went extinct
• turtle families survived

Question 3

What happens in the end-Cretaceous Extinction event (K/Pg) for crocodylians?

Answer 3

5/10 crocodylian families went extinct

Question 4

What happens in the end-Cretaceous Extinction event (K/Pg) for Pterosaurs and birds?

Answer 4

• all remaining pterosaurs go extinct

- most birds survive

Question 5

What happens in the end-Cretaceous Extinction event (K/Pg) for non-avian dinosaurs?

Answer 5

• all extinct

Question 6

What happens in the end-Cretaceous Extinction event (K/Pg) for mammals?

Answer 6

• All major groups survive

Question 7

What are the possible causes of the end-Cretaceous Extinction event?

Answer 7

Disease - no evidence in fossil record
Sea level change - yes but not enough
Climate change - yes but not abrupt
Volcanism - yes but extinction event is extremely rapid
Asteroid/comet impact - evidence found

Question 8

Breakdown the K/Pg impact events?

Answer 8

• Impact
• IR pulse
• Nuclear winter

Question 9

What did the IR pulse do in the end-Cretaceous Extinction event (K/Pg)?

Answer 9

Caused a heat pulse that killed individuals exposed
probably lasted 30 min at any given location
Probably NOT sufficient to cause global wildfires

Question 10

How did animals survive the heat pulse in the K/Pg event?

Answer 10

only sheltering taxa survive

burrow - swim - other shelters - minutes counted

Question 11

What happened following the K/Pg event?

Answer 11

– Nuclear winter caused by debris thrown into the atmosphere
– Collapse of remaining ecosystems due to lack of sunlight
– Disaster taxa (generalists) survive
– Individuals of non-sheltering taxa may have survived,
but the remnant population may not have been viable • Small populations are vulnerable to rapid extinction

Question 12

If heat pulse hypothesis is correct how long did the K/Pg event take?

Answer 12

Likely a matter of hours for the heat pulse followed by collapsing ecosystems during a nuclear winter