Magnetotellurics unveils a hidden caldera complex beneath the Cappadocia Volcanic Province, Central Anatolia, Türkiye

Abstract

The Neogene-Quaternary volcanism in central Anatolia is characterized by ignimbrite sequences, and associated calderas have been partly dismantled and buried as a result of tectonic, volcanic, erosional and depositional processes, hindering the identification of these structures from surface expressions. To search the location of a concealed caldera complex, one of the probable ignimbrite source vents, magnetotelluric data acquired at 60 stations in the period range from 0.001 s to 1000 s were used to derive an upper crustal three-dimensional electrical resistivity model in the Cappadocian Volcanic Province, central Anatolia, Türkiye. The electrical resistivity model provides constraints on the location, geometry and boundaries of a hidden caldera complex situated in the Çiftlik basin, north of Mt. Melendiz accurately, as well as its morphology at depth, which is characterized by a large depression with low resistivity values beneath the high resistivity layer consisting of pyroclastic flow deposits. This area spatially coinciding with Neogene collapse structures is interpreted as a buried caldera complex with a maximum diameter of ~12 km and depth of −3 km (below sea level) that is formed by partially overlapped nested caldera structures of subsequent volcanic eruptions and attributed to the probable source area for the Miocene-Pliocene ignimbrite emplacements. The collapse and burying process of the caldera complex have been linked with the transtensional tectonics of the Cappadocia region. Besides, the structural margins are inactive and probably bounded by faults buried under younger volcanic products within the Cappadocian Volcanic Province. The results present major implications for a better understanding of the deep three-dimensional structure of hidden caldera complexes, of which little is known, and also for describing the relationship between hidden calderas and regional tectonics.