Week 17

Question 1

Mesozoic recap

Answer 1

Pangaea break up

= massive flood basalts

Rapid seafloor spreading = mantle-derived CO2–>atmosphere and increase in MOR size

High SL = continental flooding

T +10-20’C
= forests were now tundra/ice
= no polar ice caps

Question 2

Who formed Cenozoic epochs and what are they?

Answer 2

Charles Lyell 1983

TERTIARY:
Pliocene
Miocene
Oligocene
Eocene
Palaeocene

QUATERNARY
Holocene
Pleistocene

Question 3

Eocene palaeogeography

Answer 3

India separated moving N

Austria + Antarctica

N/S America separate

Question 4

General cenozoic climate trend

Answer 4

Cooling starting with K/T event

• isotope record = ocean T/ice vol
• seismic stratigraphic studies = eustatic record

BUT PETM

Question 5

Palaeocene Eocene Thermal Maximum

Answer 5

5-8’C warming all latitudes, surface and deep oceans

Arctic surface water 18–>23’C

Question 6

Explanations for PETM

Answer 6

1. Clathrate Gun Hypothesis
   (CH4 = v low 13C signature)
   - stability due to bottom/intermediate water T
   - disassociation T driven
2. Thermostat
   - long term reduction in strength of -ve silicate weathering FB
   - flat continents/low weatherability

Question 7

Advective fluxes

Answer 7

Mass movement of energy e.g. ocean currents/atmosphere

Question 8

What happened to the Cenozoic climate after PETM?

Answer 8

Cenozoic Global Surface Cooling

Question 9

Cenozoic Global Surface Cooling facts

Answer 9

NZ brachiopod isotopes showed T 8—>13’C near Eocene/Oligocene boundary

38Ma = Antarctic sea ice

Greenhouse –> icehouse

Question 10

Explanations for Cenozoic Global Surface Cooling

Answer 10

BLAG

• seafloor spreading rates
• reduced 55-15Ma :)
• increased 15Ma-today :(

UPLIFT/SILICATE WEATHERING

• req high elevation, active mountain building, high erosion evidence in sedimentary record
• shown in 87Sr/86Sr BUT can also be formed by weathering of radiogenic rock type/decrease in hydrothermal seafloor spreading sources
• :) India+Asia ~50Ma = Tibetan-Himalayan complex (increase rainfall/sedimentary load = CO2 drawdown) :) timing

SUBTLE CONTINENTAL DRIFT + SL CHANGES = ALTER OCEAN CIRCULATION + THEREFORE POLAR HEAT TRANSPORT

Question 11

Reasons for Oi-1

Answer 11

1. Antarctic isolation
2. Critical atmospheric CO2 threshold
3. Orbital ice-climate feedbacks

Question 12

Effect of opening/closing critical gateways

Answer 12

They link major ocean basins –> change heat/salt balance

N.B. Conflicting poleward flow effect on glaciations = complex FB w/ altitude/albedo

Question 13

Drake Passage

Answer 13

B/w S America and Antarctica

Opened 25-20Ma

= Antarctica Circumpolar Current

Stopped previous warm flow from N
= accelerated G

EAIS 35Ma and WAIS 13Ma :/

Question 14

Isthmus of Panama

Answer 14

B/w N/S America

Closed 4Ma = W flowing warm Caribbean saline water now N flowing w/ Gulf Stream

Increases ocean evaporation/precipitation on land
(Less sea ice = more moisture = G)

Arctic G 2.7Ma :)

Question 15

Organic burial - factors that affect

Answer 15

PRODUCTION RATES
- nutrient supply (upwelling/delivery from land)

PRESERVATION MODES
- bottom water oxygenation

Question 16

Organic burial as a driver for climate change

Answer 16

FOR
13Ma Cali coast C-rich beds
Max organic C burial 3Ma after max cooling
= ‘Monterey Hypothesis’ = strong winds = upwelling

AGAINST
- weathering organic rich rocks?
(G = accelerates rock C oxidation; -ve FB = cooling/warming)

Question 17

How much of the Earth’s surface covered in glaciers during Plio-Pleistocene glaciation?

Answer 17

30%

Once ice caps formed, controlled by Croll-Milankovitch cycles

Question 18

N America glaciers

Answer 18

Laurentide Ice Sheet

Cordilleron Ice Sheet

(N.B. Not in Alaska/Siberia due to less moisture - supports Isthmus theory)

Question 19

Europe glaciers

Answer 19

Fennoscandian Ice Sheet

British Ice Sheet

Alpine Ice Sheet