Various marginal marine environments in the Central Paratethys: Late Badenian and Sarmatian (middle Miocene) marine and non-marine microfossils from Pécs-Danitzpuszta, southern Hungary

Abstract

The middle Miocene foraminifera and ostracod record of the Central Paratethys usually reflects stable normal marine epositional environments for the Badenian and more patchy, less stable restricted marine environments for the Sarmatian. A 17 m thick outcrop at Pécs-Danitzpuszta, Mecsek Mts, SW Hungary exposed an upper Badenian to Pannonian succession where foraminifers and ostracods document significant environmental changes. The basal layers of the section contain micro- and macrofossils indicating normal marine, shallow, warm, well-oxygenated habitat with relatively high-energy conditions and algal vegetation on the bottom, and represent the upper Badenian (13.82 to 12.65 Ma). The marine deposits are followed by coarse sandstone, breccia and siltstone layers barren of microfossils but containing rhizoliths. The sediments were probably subaerially exposed for some time. The following marine inundation, marked by the appearance of clays and limestones as well as fossils, was dated to the late Sarmatian (ca. 12 to 11.6 Ma) on the basis of the restricted marine microfossil assemblages from the upper part of the succession (Porosononion granosum Zone, Aurila notata Zone). This community is characterized by exclusively eurytopic forms indicating an unstable and vegetated marginal marine environment with fluctuations in salinity, as well as oxygen and food availability. Within the 5 m thick upper Sarmatian marine interval, a unique fresh- to oligohaline fauna characterizes a few layers in less than 1 m thickness. This fauna consists of highly euryhaline foraminifera and freshwater to oligohaline ostracod assemblages, indicating a temporary salinity reduction to 5–10 ‰. No similar freshwater fauna has been reported from the Sarmatian of the Central Partethys so far. The eventual disappearance of the foraminifera from the paleontological record coupled with a complete turnover in the ostracod fauna indicates the transition from the marginal marine Sarmatian Sea to the brackish Lake Pannon, marking the Sarmatian/Pannonian boundary (11.6 Ma).