Bedrock erodibility governs transient erosion and CO2 release in alpine landscapes.

Differences in lithology within alpine watersheds lead to strong contrasts in bedrock erodibility, which modulate climatic and tectonic influences on erosion, chemical weathering, and carbon dioxide exchange. However, the difficulty of measuring denudation rates in fine-grained rocks has limited our ability to quantify the magnitude of erodibility differences between weak sedimentary and strong igneous rocks. Here, we combine newly developed cosmogenic beryllium-10 measurements in shale with conventional beryllium-10 measurements in intrusive rocks, topographic analysis, solute data, and landscape evolution modeling in the East River watershed, Colorado. Shale-dominated catchments denude three times faster than adjacent intrusive catchments despite having gentler topography. Hydrochemical data and modeling indicate that elevated shale denudation enhances solute generation and net inorganic weathering-driven carbon dioxide release during prolonged landscape adjustment over million-year timescales. These results show that spatial variability in rock type alone can substantially alter the carbon dioxide balance of alpine landscapes by hiding the fastest erosion rates in relatively gentle terrain.