Lecture 19: Coccoliths run riot

Question 1

When did the Cretaceous start?

Answer 1

Around 145 million years ago

Question 2

When did the Cretaceous end?

Answer 2

Around 66 million years ago

Question 3

What was happening in the early cretaceous?

Answer 3

Pangea fragmenting
New ocean basins form
South Atlantic, Gulf of Mexico/ Caribbean Open
More extensive coastlines formed= vast shallow warm seas

Question 4

What happened to do with Plankton in the cretaceous?

Answer 4

Rapid radiation

Dramatic increase in diversity

Question 5

What happened to do with plants in the cretaceous?

Answer 5

New plants evolve- the plants the dominate the earth today.
Angiosperms- flowering plants
Complex reticulate pollen
Complex leaf venation
Rapid reproduction

Question 6

What is characteristic of wind pollination plants?

Answer 6

Inconspicuous flowers

Lots of small pollen grains

Question 7

What is characteristic of insect pollination plants?

Answer 7

Fewer large pollen grains
Showy flower and nectar
Rapid plant-insect co evolution

Question 8

Early cretaceous climate

Answer 8

Warm and dry
Periodic wildfires and flash floods
Seasonally cool temperatures
Cool at high latitudes

Question 9

Where can the evidence for the change in climate in the early cretaceous be found?

Answer 9

In the rocks

Question 10

Evidence for Mid Cretaceous temperature increase

Answer 10

Oxygen isotopes from calcareous fossils
Angiosperm lead shape
Distribution of fossil organisms

Question 11

Polar dinosaurs

Answer 11

Lived at poles where average annual temp around -5oC
Many probably insulated- feathers etc
Had to endure prolonged darkness around 3 months a year
Large eyes, optic lobes

Question 12

Mid cretaceous climate

Answer 12

Temperatures rise rapidly including tropical sea surface temperatures- 8 degrees hotter than today.

Question 13

What caused the temperature rise?

Answer 13

Massive increase in volcanic activity
Increased Co2 flux in atmosphere- 4-6x that of today
High sea level meant less land area = low relief = silicate weathering = less co2 removal

Question 14

What caused sea level rise?

Answer 14

No polar ice

Increased mid ocean ridge spreading pushed up sea level

Question 15

What was the different sort of ocean circulation?

Answer 15

In the mid and late cretaceous the poles were not cold.

Driven by deep water produced by sinking dense saline water from tropics?

Question 16

What did the less circulation in the ocean result in?

Answer 16

Less oxygen delivered to deep ocean
Less oxygen dissolves in warm water
Global scale deposition of organic carbon