Interpreting past environments

Question 1

What is temporal framework?

Answer 1

• A geologic time scale
• The statisfatic timescale
• Date ash beds with radiometric dating

Question 2

Spatial framework using remnant magnetism

Answer 2

• Rocks are deposited
• Metals within align to the poles
• Can plot where continents were located etc
• Plot out palaeogeography

Question 3

How has sea level and continental configuration changed over time?

Answer 3

• Both changed in the short and long term
• The extent of the shelf seas and epicontinental seas (shallow seas on the continents) has varied considerably
• Higher sea levels and more continenta shelf with higher biodiversity = more fossil preservation

Question 4

1/ The nature of sediments (relate to present day distribution).

Reconstructing past environments

Answer 4

• Sedimentologists can read rocks
• Know how rocks were deposited etc

Question 5

2/ The nature of fossil content (relate to present day distribution).

Reconstructing past environments

Answer 5

• Look at fossils and work out clues as to what the environment was.
• E.g. If echinoderms are present this is an indication of a marine environment.

Question 6

3/ The distribution of climatically sensitive sediments and fossils.

Reconstructing past environments

Answer 6

• By looking at the fossil and sediments in an area you can work out what the climate was like
• E.g. Palms and mangroves are only found in warm temperate regions

Question 7

4/ Environmentally discriminating isotopes.

Reconstructing past environments

Answer 7

• Carbon types etc.
• Look at isotopic values within fossil
• Discriminate between light and heavy boron depending on how acidic the environment was.
• Can work out how much CO2 was in the environment
• Therefore content within the atmosphere

Question 8

5/ Environmentally influenced characteristics of organisms.

Reconstructing past environments

Answer 8

• Tree growth rings
• No growth rings = tropical not seasonal
• Higher CO2 level the few stomata plants have
• Many examples of this.

Question 9

What was the configuration of the world like during the triassic when the dinosaurs evolved?

Answer 9

• Huge land mass: Pangea
• Small tethys ocean
• Huge Panthalassic ocan that covered most of the earth

Question 10

What was the configuration of the world like during the Jurassic?

Answer 10

• Early jurassic - minimal splitting
• Late jurassic - Many parts of the land splitting apart: North america split from gondwana
• Late cretaceous - Everything has split apart

Question 11

What was the configuration of the earth during the late cretaceous?

Answer 11

• Africa and south america split
• Shallow warm seas that had high diversity

Question 12

How did CO2 levels change over time?

Answer 12

Higher in triassic and gradually fall (still much higher than today’s levels)

Question 13

How have O2 levels changed?

Answer 13

• Less O2 than today
• Less forest fires
• Carboniferous - high O2 lots of forest fires

Question 14

When was the greenhouse world?

Answer 14

• Triassic, jurassic and cretaceous
• High CO2 levels

Question 15

What is a polar forest?

Case study: Polar dinosaurs

Answer 15

• Polar regions had no ice (greenhouse world)
• Warmer climates in the past had forests
• Forests at the poles
• Cool / temperate forests
• Forests thrived in summers (sun didn’t set)
• 6 months darkness (shed leaves)
• No such thing as a polar forest today
• High CO2 regimes of weird sunlight

Question 16

What is unusual about footprints being foung in the arctic circle?

Answer 16

• Why was a dinosaur in the arctic circle?
• Before plate techtonics
• Reptiles could not survive in arctic winters (need sunlight)

Question 17

What do the arctic footprints possibly show?

Answer 17

• Possible evidence of migration in the north pole but not possible in the south
• Possible hibernation? No evidence for LAGs in any dinosaur bones from the polar regions.
• Warm blooded? Possible that there were some warm blooded or intermediate blooded. Featherlike structures could have given protection from the cold.

Question 18

What does dinosaurs with large eyes tell us about their adaptations?

Answer 18

• Large eyes suggest they were active over the winter
• Large eyes suggest dinosaurs adapted for polar winters.
• Moved arounf by moonlight