Upper Acıgöl Tuff: Eruption dynamics of the youngest Cappadocian ignimbrite

The Late Pleistocene Lower and Upper Acıgöl Tuffs (LAT and UAT; 190 ± 11 ka and 164 ± 4 ka) represent the two most recent major ignimbrite eruptions on the Cappadocia Plateau in the Central Anatolian Volcanic Province. Both Acıgöl ignimbrite eruptions correspond to VEI 6 events, with caldera collapse and regionally widespread dispersal of tens of km³ of tephra. Understanding syn-caldera eruptive processes is critical for volcanic hazard assessment in regions such as Cappadocia, where active volcanic systems coexist with dense populations and intense tourism. Although previous studies of the Acıgöl caldera complex have constrained eruption ages, stratigraphy, and geochemistry, the latest syn-caldera eruptive processes associated with UAT ignimbrite emplacement remain poorly resolved. Here we reconstruct the eruptive history of the UAT through proximal volcanostratigraphy, integrated with glass geochemistry and previous published geochronology. The stratigraphic record within the caldera documents a continuous succession of deposits including a phreatomagmatic tephra ring, debris-avalanche deposits derived from the Koçadağ intra-caldera dome, lithic-rich Plinian fallout, caldera-forming ignimbrite, and post-collapse lava-dome emplacement. Our results indicate that the Taşkesik intra-caldera maar eruption occurred during the early stages of the UAT caldera-forming eruption. While not a deterministic precursor, this small-scale event could represent the onset of a cascade of processes that ultimately led to magma chamber decompression, roof subsidence, and ignimbrite emplacement associated with caldera collapse. This refined syn-caldera framework at Acıgöl provides new constraints on caldera-collapse dynamics and has direct implications for hazard assessment in active caldera systems.This work was funded by the Spanish Ministry of Science and Innovation (TURVO, PID2023-147255NB-I00; MCIN/AEI/10.13039/501100011033), the EU (ERDF; Horizon 2020–MSCA PÜSKÜRÜM, Grant 101024337), and the Italian PNRR–NextGenerationEU through the ÇoraDrill project (CUP B83C25001180001).