TESTING THE CONTROL OF MINERAL SUPPLY RATES ON CHEMICAL WEATHERING IN THE KLAMATH MOUNTAINS

Several decades of research have shown that the sensitivity of chemical erosion rates to mineral supply rates is at the center of many problems in Earth science, including how tightly Earth’s climate should be coupled to tectonics, how strongly nutrient supply to soils and streams depends on soil production, and how much lithology affects landscape evolution. Despite widespread interest in the subject, there remains no consensus on how closely coupled chemical erosion rates should be to mineral supply rates. To address this, we have established a network of field sites in the Klamath Mountains along a latitudinal transect that spans an expected gradient in mineral supply rates associated with the migration of the Mendocino Triple Junction. Previous studies suggest a balance between rock uplift rates and basin wide erosion rates, implying an equilibrium landscape in our study region. Our sites are comprised of a series of granodioritic ridgetops, where we have collected bedrock and regolith samples from the surface to the soil/saprolite interface. From these sites, measurements of the chemical depletion fraction (CDF) and mineral supply rates inferred from cosmogenically-produced ¹⁰Be will be used to test hypotheses of supply-limited and kinetically-limited chemical weathering. Our data will provide useful insight into the coupling between chemical weathering rates and those of mineral supply.