Lack of a weathering signal with increased Cenozoic erosion?

Abstract

AbstractThe Late Cenozoic has been marked by large and rapid fluctuations in temperature. This cooling has been attributed to accelerated erosion, with concomitant increased chemical‐weathering rates and CO2 drawdown from the atmosphere. At the same time, much of the supporting evidence appears to be affected by a sampling bias, implying that global erosion and weathering have remained largely constant over the past millions of years. We suggest that sedimentary archives of geomorphic activity, such as grain size and the ratio of terrestrial to oceanic sedimentation, which show accelerated erosion are not subject to these biases. Furthermore, the active tectonic settings where these erosion increases were likely to have taken place are exactly those locations where chemical‐weathering signals are least likely to faithfully follow physical erosion rates. A lack of evidence for an increase in chemical weathering does not necessarily preclude an increase in physical erosion. In this contribution, we suggest an alternative interpretation in which erosion rates have increased in the Late Cenozoic but without significantly increased silicate weathering, which can explain the meagre response of chemical‐weathering proxies.