Dr. Peter Clift (University College London)

Mountain Building, Erosion, and Chemical Weathering as Triggers of Cenozoic Global Cooling

Abstract: Climate is controlled to a large extent by atmospheric CO2 levels over geological time scales. CO2 concentrations reflect a balance between mantle outgassing during volcanism and chemical weathering of silicate rocks and subduction of C-bearing sediments back into the mantle. Global subduction budgets point to long-term net subduction of carbon during the Cenozoic removing carbon from the surface. Silicate weathering has also been linked to mountain building and especially the uplift and erosion of the Himalayas and Tibetan Plateau. Following a campaign of drilling Asian marginal seas it is now practical to estimate weathering and organic carbon burial fluxes in South and East Asia at least during the Neogene. These indicate a sharp rise since the Pliocene but much less impact earlier in the Miocene calling into question the role of India-Asia collision as a climate influence since ~24 Ma. Instead the role of weathering in low latitude arcs and ophiolite belts of the Maritime Continent may have been more important. Estimates from New Guinea imply that this was more impactful to global CO2 level than the Himalayas starting in the Late Miocene. Furthermore, enhanced weathering of extensive tropical continental shelves, especially Sunda Shelf, is now revealed as a crucial modulator of glacial cycles, enhancing cycle amplitude since the subsidence of Sunderland since the Mid Pleistocene Transition.

Invited by: Alex Webb