The volcanic evolution and eruption dynamics of the youngest Cappadocian caldera-forming ignimbrite. The Upper Acıgöl Tuff, Central Anatolia (Turkey)

Acıgöl caldera (Central Anatolia, Turkey) offers an exceptional natural laboratory to investigate how small-scale eruptions and large caldera-forming events may become closely coupled during the evolution of silicic volcanic systems. Here we reconstruct the eruptive evolution of the Upper Acıgöl Tuff (UAT; ~ 164 ka) using proximal volcano-stratigraphy integrated with glass chemical fingerprints and published geochronology. The intra-caldera stratigraphic record documents a continuous succession of deposits, including a phreatomagmatic tephra ring, debris-avalanche deposits, lithic-rich Plinian fallout, caldera-forming ignimbrite, and post-collapse lava-dome emplacement. The lack of evidence for long hiatuses between these units, including the absence of paleosols or reworked horizons, continuous stratigraphic contacts, local interbedding, and faulting that affects multiple units prior to lava-dome emplacement, is consistent with rapid emplacement and partial overlap among these eruptive processes. Our observations indicate that the Taşkesik maar eruption occurred during the early stages of the UAT caldera-forming event. Although not a deterministic precursor, this small-scale eruption marked an early phase of the cascading eruptive events that culminated in magma chamber decompression, roof subsidence, and ignimbrite emplacement during caldera collapse. Taşkesik and the UAT are thus regarded as closely related eruptive phenomena within a progressively evolving caldera system. These findings highlight the importance of integrating small-volume intra-caldera eruptions into conceptual models of caldera unrest and volcanic hazard assessment.