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Earth history and life - 29202 > Early cenozoic climate history > Flashcards

Early cenozoic climate history Flashcards

1
Q

What large scale geological events occurred in the Eocene?

A

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

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2
Q

What are the 3 main types of proxy?

A

Biotic
Geochemical
Sedimentary

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3
Q

What are biotic proxies?

A

Based on environment-controlled distribution of species

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4
Q

What is an example of biotic proxies?

A

Tropical and sub-tropical distribution of palms

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5
Q

What are geochemical proxies?

A

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

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6
Q

What are sedimentary deposits?

A

Based on environment-controlled deposition of sediments

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7
Q

What are some examples of climate archives?

A

Marine sediments
Ice cores
Corals
Speleothems
Tree rings

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8
Q

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

A

Oxygen isotopes in foraminifera

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9
Q

What is the abundance of O16 and O18 like?

A

O16 lighter and has higher abundance
O18 heavier and less abundant

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10
Q

What are foraminifera?

A

heterotrophic amoeboid protozoa

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11
Q

Where would you find foraminifera?

A

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

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12
Q

What have some foraminifera be able to produce?

A

Calcareous shell (calcite)

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13
Q

What does a positive O18 value mean?

A

There is relatively more of isotope O18

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14
Q

What do foraminifera host?

A

symbiotic algae

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15
Q

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

A

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

2) Changes in the oxygen isotopic composition of seawater

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16
Q

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

A

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

17
Q

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

A

increased by 0.25% per mil

18
Q

What is the effect of ice sheets on O18?

A

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

19
Q

What has happened to O18 values over time?

A

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

20
Q

Why is the cenozoic important?

A

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

21
Q

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

A

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

22
Q

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

A

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

23
Q

What is evidence of warmer Palaeogene in the Arctic?

A

Fern and duckweed linking to same as modern day black sea

24
Q

How were levels of organic carbon seasonally controlled?

A

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

25
Q

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

A

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

26
Q

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

A

North Atlantic LIP (Icelandic hotspot)

27
Q

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

A

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

28
Q

What was the effect of warming on terrestrial ecosystems cenozoic?

A

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

29
Q

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

A

Late Eocene

30
Q

What occurred in Greenland which is evidence for early glaciation?

A

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

31
Q

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

A

Diatoms which are usually associated with sea ice

32
Q

What was the main driver of a cooler climate?

A

The east Antarctic ice sheet

33
Q

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

A

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

34
Q

When was the first major expansion of Antarctic ice sheets?

A

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

35
Q

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

A

Switch to deep marine as regression occurs

Earth history and life - 29202 (29 decks)

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