The Effect of Late Cenozoic Glaciation and Tectonic Uplift on Silicate Weathering Rates and the Marine 87Sr/86Sr Record

Abstract

It is widely accepted that the consumption of atmospheric CO2 by silicate weathering provides a negative climate feedback mechanism, and that this mechanism has played an important role in moderating global climate over geological timescales (see e.g., Berner1). Extension of this concept to feedbacks between climate change and tectonic uplift, which are discussed in many chapters of this volume, is dependent on the assumption that glaciation and tectonic uplift lead to increased rates of chemical weathering and CO2 consumption. Both glaciation and rapid uplift are accompanied by rapid physical denudation, which exposes fresh bedrock minerals to the agents of chemical weathering. In addition, tectonic uplift may create mountain ranges capable of sustaining alpine glaciers and ice sheets, especially during glacial maxima, thus linking uplift and glaciation on geological timescales. While it is generally accepted that glaciation and uplift will lead to accelerated rates of chemical weathering as compared to regions of nonglaciated or stable topography, the magnitude of this effect has proven difficult to estimate. Taylor and Blum2 investigated the relation between soil age and silicate weathering rates and found a well-defined power law relation for young soils (≤ 138 thousand years old), suggesting that predictions could be made of the effect of glaciation and tectonic uplift on silicate weathering rates by considering the effect of these processes on average soil ages over large geographic areas.