Correlation of ignimbrites in the central Anatolian volcanic province using zircon and plagioclase ages and zircon compositions

Abstract

Episodes of high eruptive fluxes (>10−3km3/year) in continental environments are associated with magmatism related to subduction, post-orogenic collapse, intra-plate hot spots, or rifting. During such episodes, voluminous ignimbrite deposits are produced which cover landscapes over 104–105km2. In such sequences, brief eruptive recurrence and chemical similarity limit the applicability of geochronological and geochemical correlation methods. Here, we present complementary geochronological data (40Ar/39Ar plagioclase eruption and 206Pb/238U zircon crystallization ages) for ignimbrites from the Miocene–Holocene Central Anatolian Volcanic Province (CAVP). In addition, we successfully employed zircon geochemistry (trace elements, oxygen isotopes) as an alteration-resistant indicator to correlate rhyodacitic to rhyolitic ignimbrites whose eruption age differences are too brief to be resolved by 40Ar/39Ar geochronology. By applying this method, we dismiss previous correlations between stratigraphic members (i.e., Sofular and Gördeles, Sofular and Sarımadentepe), but demonstrate close relationships for other CAVP ignimbrites (i.e., Kavak units 1 to 4; Cemilköy ignimbrite and overlying fallout deposits). Our chronostratigraphy reveals two previously unrecognized eruptive pulses at ~9–8Ma and 7–5Ma which are characterized by increasing magmatic temperatures (~75–100°C within each cycle). Despite a long-term (10Ma) eruptive productivity that is about one order of magnitude smaller than in other magmatically active continental plateaus, the CAVP achieved high eruptive fluxes during brief (1–2Ma) intervals.