Paleosols and volcanic rocks weathering: Insights into climate and CO2 consumption during interglacial peaks
Paleosols are exceptional paleoenvironmental archives, yet they remain underutilized in geoscience research. Unlike marine or ice cores, they often lack temporal continuity. However, their direct formation at the atmosphere–lithosphere interface makes them particularly sensitive to terrestrial paleoclimatic signals and local responses to global changes.
Over the past five years, our team has investigated paleosols formed through the weathering of volcanic rocks in the Azores volcanic archipelago. By combining geochemical analyses of these weathering profiles with geochronology of the over- and underlying volcanic units (K-Ar, 40Ar/39Ar), we have reconstructed regional paleoclimate (past temperature and precipitation) and quantified rates of soil formation and elemental loss. As weathering consumes atmospheric CO2, our work brings new insights into the long-term carbon cycle and climate dynamics.
Our results reveal intense soil formation during interglacial peaks, with weathering rates and CO2 uptake comparable to tropical settings, despite the Azores' temperate modern climate. These weathering pulses likely reflect climatic conditions, driven by a weakened or southward-shifted Azores High, affecting not only local hydrology but possibly climate over Europe and NW Africa. The associated bursts of volcanic weathering and carbon drawdown may have played a larger role than previously thought in promoting transitions into glacial periods.
Currently, we are applying uranium-series disequilibria to directly date weathering profiles (in ITES). A preliminary comparison with rates obtained from the geochronology of bracketing volcanic units shows promising results, and a recent field campaign aims to refine this approach, potentially establishing U-series as a novel tool for paleosol research.
By extending this research to other volcanic regions, such as the Andes or additional Atlantic islands, we aim to improve our understanding of Earth's carbon cycle and weathering–climate feedbacks over Quaternary timescales. Paleosols also hold further paleoenvironmental potential, including isotopic analyses of pedogenic carbonates for reconstructing paleoprecipitation and atmospheric pCO2.