Volcanology, Geochemistry, and Geochronology of the Kilistra Ignimbrites: Insights into Pyroclastic Density Current Emplacement in a Structurally Controlled Basin, Erenlerdag-Alacadag Volcanic Complex (SW Konya, Turkiye)

Abstract

In this study, field observations together with geochemical, geochronological, and GIS-based data provide constraints on the eruptive history of the Kilistra Ignimbrites of the Erenlerdag-Alacadag Volcanic Complex (ErAVC, SW Konya, Turkiye) and on the emplacement of pyroclastic density currents (PDCs) within a structurally controlled basin setting. The ignimbrite succession comprises four main units-Erenkaya, Evliyatekke, Detse, and Sadıklar-with Erenkaya being volumetrically dominant (similar to 90%), whereas Kızılören represents an older (>10.9 Ma) and stratigraphically distinct unit. Petrographic characteristics indicate systematic variations among the ignimbrite units. The Erenkaya Ignimbrite is crystal-rich, variably welded, and contains abundant pumice and volcanic lithic fragments. In contrast, the Evliyatekke and Sadiklar Ignimbrites are pumice-rich and weakly to non-welded, preserving well-developed tube-vesicle textures. The Detse Ignimbrite is characterized by pervasive alteration affecting crystals, lithics, pumice clasts, and matrix. Whole-rock geochemistry indicates that Erenkaya compositions are relatively coherent within the andesite-dacite range and are consistent with calc-alkaline affinities, whereas younger units show greater variability, likely reflecting magmatic differentiation and/or post-emplacement modification. The Erenkaya Ignimbrite is subdivided into three flow units separated by paleosols and erosional surfaces and is characterized by vertical welding zonation, fiamme development, and columnar jointing, indicating emplacement under high-temperature conditions. Zircon U-Pb ages define two main eruptive episodes (similar to 9.2 Ma and similar to 8.0 Ma), separated by an inter-eruptive sedimentary succession represented by intercalated fluvial-lacustrine deposits. Isopach patterns and facies variations are consistent with dispersal from the northern sector of the ErAVC, with flow pathways influenced by paleotopography and basin morphology. Welding zonation and lateral facies transitions suggest spatially variable PDC conditions, evolving from concentrated high-temperature flows to more dilute and cooler regimes during transport. These results provide new constraints on ignimbrite emplacement in structurally controlled basin settings and highlight the role of paleotopography in influencing PDC dynamics and deposit architecture.