The Sarikavak Tephra, Galatea, north central Turkey: a case study of a Miocene complex plinian eruption deposit

摘要: Abstract The Sarikavak Tephra from the central Galatean Volcanic Province (Turkey) represents deposit of a complex multiple phase plinian eruption Miocene age. eruptive sequence is subdivided into Lower-, Middle-, and Upper (LSKT, MSKT, USKT) which differ in type deposits, lithology mechanisms. Lower characterised by pumice fall deposits with minor interbedded fine-grained ash beds lower LSKT-A. Deposits are well stratified enriched lithic fragments up to >50 wt% some layers. upper LSKT-B mainly reversely graded amounts lithics. It main eruption. LSKT-A B units separated each other deposit. Middle predominantly composed cross-bedded ash-and-pumice surge MSKT-A major pyroclastic flow MSKT-B unit. shows subaerial laminated USKT-A subaqueous tephra USKT-B. Isopach maps LSKT as fine at LSKT-A/B boundary indicate NNE–SSW extending depositional fans source area western part Ovacik caldera. MSKT form SW-extending lobe related paleotopography where thickest. Internal bedding distribution result intermittent activity due significant vent wall instabilities. Reductions power (partial) plugging produced near-vent locations subsequent explosive expulsion rock debris was responsible for high contents lapilli deposits. A period closure promoted deposition end evolved stable conditions after initial gravitational column collapses during early ascent re-established plume. surges interpreted phreatomagmatic prior formation MSKT-B.