Early cenozoic climate history

Question 1

What large scale geological events occurred in the Eocene?

Answer 1

Major volcanic activity with N Atlantic rifting
Alpine uplift
Drakes passage and Tasman gateway open (Antarctic circulation)
India - early collision with Asia

Question 2

What are the 3 main types of proxy?

Answer 2

Biotic
Geochemical
Sedimentary

Question 3

What are biotic proxies?

Answer 3

Based on environment-controlled distribution of species

Question 4

What is an example of biotic proxies?

Answer 4

Tropical and sub-tropical distribution of palms

Question 5

What are geochemical proxies?

Answer 5

Based on the environment-controlled chemistry of geological materials, including fossil shells, organic biomarkers, mineral deposits

Question 6

What are sedimentary deposits?

Answer 6

Based on environment-controlled deposition of sediments

Question 7

What are some examples of climate archives?

Answer 7

Marine sediments
Ice cores
Corals
Speleothems
Tree rings

Question 8

What is the primary proxy for ocean temperature and planetary ice volume?

Answer 8

Oxygen isotopes in foraminifera

Question 9

What is the abundance of O16 and O18 like?

Answer 9

O16 lighter and has higher abundance
O18 heavier and less abundant

Question 10

What are foraminifera?

Answer 10

heterotrophic amoeboid protozoa

Question 11

Where would you find foraminifera?

Answer 11

Free floating in the surface oceans (planktonic) and on/in sediment surface at the bottom of the seas / oceans (benthic)

Question 12

What have some foraminifera be able to produce?

Answer 12

Calcareous shell (calcite)

Question 13

What does a positive O18 value mean?

Answer 13

There is relatively more of isotope O18

Question 14

What do foraminifera host?

Answer 14

symbiotic algae

Question 15

What 2 factors can the variations of O18 recorded by foram CaCO3 be attributed to?

Answer 15

1) Temperature-dependent fractionation of isotopes between water (seawater) and calcite (foraminifera)

2) Changes in the oxygen isotopic composition of seawater

Question 16

What can change the composition of O18 ration in sea water and freshwater?

Answer 16

Warmer temp will led to higher O18 in ocean as lighter O16 preferred
Lower O18 in water vapour as its heavier and condenses easier

Question 17

WHat does a 1*c change do to the O18 value in foram shells?

Answer 17

increased by 0.25% per mil

Question 18

What is the effect of ice sheets on O18?

Answer 18

Ice sheets lock up O18 depleted water for Ka to Ma thus making oceans O18 +

Question 19

What has happened to O18 values over time?

Answer 19

Became more positive with a link to cooling deep oceans and glaciation around 30 Ma

Question 20

Why is the cenozoic important?

Answer 20

Provides one of the best records for the effect of higher co2 ppm with a max of 1900 ppm

Question 21

What is an indicator of how hot the Palaeogene greenhouse earth was?

Answer 21

Supported an boa 13m which would have needed mean temp of 35*c

Question 22

How can Antarctica be evidence for how warm Palaeogene greenhouse earth was?

Answer 22

Palm pollen
Biomolecular data show ~20*c warmer (sub-tropical)

Question 23

What is evidence of warmer Palaeogene in the Arctic?

Answer 23

Fern and duckweed linking to same as modern day black sea

Question 24

How were levels of organic carbon seasonally controlled?

Answer 24

6 months of darkness experienced due to the tilt of the poles

Question 25

What is the a balance between in the carbon cycle on a million year timescale?

Answer 25

CO2 input to atmosphere: volcanism related to rifting and spreading
CO2 removal from the atmosphere: chemical weathering of silicate rocks, organic carbon burial

Question 26

What was one of the main volcanic sources of carbon dioxide in the eocene?

Answer 26

North Atlantic LIP (Icelandic hotspot)

Question 27

What was a cause of a 200,000 year warming period in the Eocene?

Answer 27

Increased calcium carbonate in oceans as a result of it being eroded by carbonic acid

Question 28

What was the effect of warming on terrestrial ecosystems cenozoic?

Answer 28

Forest habitats expanding into high latitude and opening up migration routes for early primates to move from Eurasia to the Americas

Question 29

How far back is there evidence for ice rafted debris and thus glaciers?

Answer 29

Late Eocene

Question 30

What occurred in Greenland which is evidence for early glaciation?

Answer 30

Sporadic expansion of valley glaciers and calving of icebergs into Greenland sea

Question 31

What organic evidence is there for glaciation in the late Eocene?

Answer 31

Diatoms which are usually associated with sea ice

Question 32

What was the main driver of a cooler climate?

Answer 32

The east Antarctic ice sheet

Question 33

What was the development of the East Antarctic ice sheet driven by?

Answer 33

Ice sheets merge, buffer and ice-albedo feedbacks
Geologically rapid transition (10*5 years)

Question 34

When was the first major expansion of Antarctic ice sheets?

Answer 34

Eocene-Oligocene boundary (shown by switch in O18 value becoming more positive)

Question 35

How does deposition environment for limestone change as a result of glaciation?

Answer 35

Switch to deep marine as regression occurs