Weathering pulses during glacial-interglacial transitions: Insights from well-dated paleosols in the Azores volcanic province (Central North Atlantic)

Volcanic islands evolve through complex interactions between volcano growth and surface processes. Climate changes impact the physical and chemical processes that drive weathering and denudation. While global paleoclimate has been extensively studied for the late Quaternary, elucidating the local climatic response to global forcing on such islands remains challenging. S & atilde;o Miguel is a volcanic island in the Eastern Azores, located in the Central North Atlantic, a region susceptible to changes in large-scale atmospheric and oceanic dynamics. It comprises numerous paleosols (PSs), whose geochemistry results from volcanic rocks' weathering and can serve as a proxy to reconstruct paleoclimatic conditions. New K-Ar and Ar-40/Ar-39 ages of volcanic units "bracketing" (under and overlying) PSs reveal four periods of enhanced soil formation (similar to 820-765 ka, similar to 425-430 ka, similar to 170-75 ka, <10 ka), coinciding with rapid glacial-interglacial transitions (Terminations I, II, V, IX). Our reconstructed mean annual precipitation (MAP; 500-1200 mm yr(-1)) and air temperature (MAAT; 12-18 degrees C) are higher during interglacial peaks. This, in addition to the coherence of MAAT with previous Sea Surface Temperature reconstructions, shows consistency between local and global climate dynamics. The texture of parental rocks played a significant role in weathering, with PSs predominantly restricted to the brecciated upper part of lava flows and to pyroclastic deposits, which exhibited distinctive precipitation thresholds for their formation (similar to 800 mm yr(-1) and similar to 500 mm yr(-1), respectively). PSs developed on basaltic lava flows exhibit greater elemental loss, due to a high glass proportion and low permeability, which prevents fluids percolation out of the soils. As present-day precipitation and temperature exceed those of the past, enhanced weathering is expected in S & atilde;o Miguel and other volcanic islands, with local to global impacts (e.g., carbon cycling), especially in the context of ongoing global warming.