Surface uplift of Tibet and Cenozoic global cooling

Abstract

Continental weathering on a global scale infl uences ocean chemistry and imposes a net drawdown of atmospheric CO 2 that modulates global climate (Walker et al., 1981; Berner et al., 1983). This observation, in addition to seawater Sr records that suggest an increase in continental weathering after ca. 40 Ma, led researchers to suggest that the uplift and erosion of the Himalayan-Tibetan orogen over the past 40 m.y. has drawn down atmospheric CO 2 and cooled the globe, leading to the glacial climate that persists today (e.g., Raymo and Ruddiman, 1992; Edmond, 1992). Modeling of tectonic-climate feedbacks associated with increased weathering of the Himalaya and Tibet suggests that two primary biogeochemical processes , silicate weathering and organic carbon burial, can account for the lowering of atmospheric CO 2 necessary to force global cooling (Raymo et al., 1988; Zachos and Kump, 2005). At the time of these inferences, accurate records of both atmospheric pCO 2 and the surface uplift history of the Himalaya and Tibet were lacking. Now, in light of a growing body of atmospheric pCO 2 reconstructions and paleoelevation records, we can test the theory that increased weathering associated with growing mountain belts leads to the drawdown of atmospheric CO 2 and global cooling. The Eocene-Oligocene transition (EOT) at ca. 34 Ma marks the fi rst major decline in Cenozoic global temperatures and the initiation of Antarctic glaciation. Critical to the argument that continental weathering has caused the drawdown of atmospheric CO 2 is documentation of the temporal relationship between the surface uplift of the Himalayan-Tibetan