Late miocene ostracodes of Serbia: Morphologic and palaeoenvironmental considerations

Abstract

About 11.5 million years ago, a tectonic uplift of the Eastern and Western Carpathians separated the Pannonian Basin from the rest of the Paratethys. This orogenesis event caused an unconformity between the Sarmatian brackish sediments and the Pannonian lake-sea deposits. More than 6 Ma later, in these parts of the Paratethys, changes in the geographic framework, hydrological conditions and brackish - caspibrackish water chemistry led to the disappearance of restricted marine forms of life. A few euryhaline and marginal marine species survived this environmental change. Among the ostracodes, some originally freshwater taxa, such as Candoninae, entered the lake-sea. Many lineages show gradual morphological changes. The older, low diversity ostracode fauna from the Lower Pannonian dispersed to the endemic species and genera during the Upper Pannonian. This interval is assigned as the "bloom time" for many ostracodes, both qualitatively and quantitatively. This time sequence is the last appearances of genera such as Aurila Cytheridea, Propontoniella, etc. and simultaneously, the first appearances for many new genera, such as Zalanyiella, Serbiella, Camptocypria Sinegubiella etc. During the Pontian, migration processes were present. Therefore, it can be supposed that many eastern Paratethyan forms have Pannonian origin.Na prelazu izmedju srednjeg i gornjeg miocena, pre oko 11,5 miliona godina tektonska izdizanja u Karpatima su dovela do odvajanja Panonskog prostora od ostatka Paratetisa. To je rezultiralo diskordancijom izmedju sarmatskih brakicnih i panonskih, kaspibrakicnih naslaga. Skoro 6 miliona godina kasnije, promene geografskih prilika, hidroloskih uslova i formiranje osladjene vodene sredine, dovele su do potpunog izumiranja morskih organizama. Samo nekoliko evrihalinskih formi kao i onih koji su nastanjivali priobalne delove uspelo je da se prilagodi i prezivi. Kod ostrakoda, slatkovodni oblici poput kandonina, sve vise nastanjuju takvo veliko jezero-more dok neki filogenetski nizovi pokazuju postepene izmene. Starije panonska, slabije raznovrsna ostrakodska fauna evoluira u neke endemicne oblike tokom mladjeg panona kada dolazi i do pravog procvata ostrakoda, kako po broju vrsta tako i po broju jedinki. To je period poslednjeg pojavljivanja rodova Aurila Cytheridea, Propontoniella odnosno vreme prvog pojavljivanja rodova Zalanyiella, Serbiella, Camptocypria, Sinegubiella. Za vreme ponta, zapazeni su migracioni procesi na ovom prostoru i smatra se da mnogi oblici koji zive u istocnom Paratetisu imaju panonsko poreklo.