Earth’s climate history

Cenozoic cooling

CaCO3 is taken up by marine organisms

CoccolithophoridForaminifer

... as is SiO2

Diatom (SiO2) (50microns)Radiolarian (SiO2) (50 microns)

Carbon reservoirs today

Destination of atmospheric CO2

Inorganic carbon cycle

Carbon ends up here

Volcanic eruptions main source of CO2

BLAG model – spreading rates sometimes fast, sometimes slow

Pre-Quaternary atmospheric CO2 levels cannot yet be directly determined.

Can be modeled from the carbon isotope record?BLAG (Berner, Lasaga, Garrels) Model

Steady-State Flux Balance EquationFwc +Fmc + Fwg = Fbc + Fbgw: weatheringm: metamorphismb: burialc: carbonateg: organic

Ocean andatmosphere

C

CarbonateC Organic

C5000

1250

2.9

Fwc Fwg

FbgFbcFmc Fmg

Climate through Earth history

Cenozoic cooling

Spreading rates have decreased over last 65 million years

Silicate rock weathering

Weathering rates increase over Cenozoic

• Does the amount of high elevation terrain result in unusual physical weathering?

• Most likely given 10 fold increase of sediment to the Indian Ocean– Steep terrain along

southern Himalayan margin

– Presence of powerful South Asian monsoon

Tibetan plateau

Changes in amount of uplift of continental rockcould regulate amount of weathering

“Upliftweatheringhypothesis”

Uplift mainlywhen continentscollide

Climate through Earth history