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EARLY AND MIDDLE MIOCENE VOLCANICLASTIC RECORD ON MTS. KALNIK AND POŽEŠKA GORA

The formation and evolution of the Pannonian Basin as part of the Carpathian-Pannonian Region (CPR) was accompanied by voluminous silicic eruptions during Early and Middle Miocene [1]. Silicic pyroclastic material, which covered much of the CPR, can be found in Miocene deposits in the North Croatian Basin (NCB, SW part of Pannonian Basin). This research is focused on two main outcrops of volcaniclastic rocks on Mts. Kalnik and Požeška Gora. Samples are in a procces of analyses using a ”multi-proxy“ approach, combining sedimentological, petrological and paleontological data, high-precision zircon geo(petro)chronology, 40Ar/39Ar radiometric dating along with geochemistry and isotopic composition of volcanic glass and minerals. First results from Mt. Kalnik volcaniclastic deposits characterized them as massive rhyolitic ignimbrites with a CA-ID-TIMS U-Pb zircon age of 18.06 ± 0.023 Ma [2]. These results indicate that potentially correlative volcaniclastic deposits are intercalated with marine sediments in the Hrvatsko Zagorje Basin and lake sediments in the Sinj Basin. Guided by results from Avanić [3] and de Leeuw [4], we sampled nine additional volcaniclastic outcrops. Furthermore, deposites that might be correlative with Mt. Požeška gora primary volcanoclastic turbidites are found on Mt. Medvednica intercalated in marine sediments of Central Paratethys. New CA-ID-TIMS zircon ages indicates that the initial Middle Miocene marine flooding of the western part of the NCB (Mt. Medvednica) could have occurred contemporaneously with its eastern part (Mt. Požeška Gora, 15.345 ± 0.02 Ma, [2]). Integrated data will enable more reliable tephrochronological and volcanic provenance, as well as petrogenetic reconstructions of Mts. Kalnik and Požeška Gora volcaniclastic deposits. This work is supported by the Croatian Science Foundation through project „Miocene syn-rift evolution of the North Croatian Basin (Carpathian-Pannonian Region): a multi-proxy approach, correlation and integration of sedimentary and volcanic record“ (PYROSKA), (UIP-2019-04-7761).

geochronology, tephrostratigraphy, miocene, North Croatian Basin

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