Earths climate history Cenozoic cooling Ca CO 3

Earth’s climate history

Cenozoic cooling

Ca. CO 3 is taken up by marine organisms Coccolithophorid Foraminifer

. . . as is Si. O 2 Diatom (Si. O 2) (50 microns) Radiolarian (Si. O 2) (50 microns)

Destination of atmospheric CO 2 Carbon reservoirs today

Inorganic carbon cycle Carbon ends up here

Volcanic eruptions main source of CO 2

BLAG model – spreading rates sometimes fast, sometimes slow

Pre-Quaternary atmospheric CO 2 levels cannot yet be directly determined. Can be modeled from the carbon isotope record? BLAG (Berner, Lasaga, Garrels) Model Steady-State Flux Balance Equation Fwc +Fmc + Fwg = Fbc + Fbg w: weathering m: metamorphism b: burial c: carbonate g: organic

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 rock could regulate amount of weathering “Uplift weathering hypothesis” Uplift mainly when continents collide

Climate through Earth history