Miocene paleogeography and biostratigraphy of the Slovenj Gradec Basin: a marine corridor between the Mediterranean and Central Paratethys

Abstract

The Miocene evolution of the area transitional from the Eastern Alps to the Pannonian Basin System was studied through the paleogeographic evolution of the Slovenj Gradec Basin in northern Slovenia. It is based on mapping, section logging, nannoplankton biostratigraphy, and petrography. The results are correlated with the lithological column of the borehole MD-1/05. The evolution of the basin is connected with the development of the Pannonian Basin System, and the global 3rd order cycles, which influenced the connection with the Mediterranean Sea. Sedimentation started in the Karpatian in a fluvial to lacustrine environment and terminated at the end of the Early Badenian. During this period, three transgression–regression cycles were recorded. The first transgression occurred in the Karpatian and corresponds to the TB 2.2. cycle. The sediments reflect proximity of the hinterland. After a short break in sedimentation, the Early Badenian deposition followed. It marks the second transgression into the SGB, the first Badenian, correlated with the TB 2.3 cycle. There are signs of a transitional environment, which evolved to marine in advanced stages. At the high-stand system tract, the sea flooded the entire Slovenj Gradec Basin. Subsequent reduced quantity and diversity of the microfossils marks the onset of the second regression stage. It is followed by the third transgression, the second in the Badenian, correlated with the TB 2.4 cycle. The late Early Badenian deposition continued in the lower-energy, though occasionally still turbulent environment. Silty sediments with upward increasing content of organic matter indicate shallowing of the basin, until its final diminishing. Layers of fresh-water coal already bear witness to the existence of restricted swamps. After the Early Badenian, the area of the Slovenj Gradec Basin became dry land, exposed to erosion.

Relationship between magnetic fabrics and deformation of the Miocene Pohorje intrusions and surrounding sediments (Eastern Alps)

“…6) do not support this latter interpretation. New biostratigraphic data of Ivančič et al (2018) suggest that the sediments in the Slovenj Gradec Basin are mostly Badenian, somewhat younger than the postulated Karpatian age of the northern Pohorje Mts. ; this would favor scenario 2, but we cannot exclude explanation 1.…”

“…Therefore, calcareous nannoplankton assemblage from the upper 860 m of the MD-1 borehole ( Fig. 1) yielded NN4 and NN5 zones, representing Early to Middle Miocene (Karpatian to middle Badenian, ~ 17.2-14 Ma age, Ivančič et al 2018). Below 860 m to a total depth of 1260 m, the section mostly represented slope sediments and was barren of calcareous nannofossils; hence, no biostratigraphic attribution was possible and an early Miocene age was proposed (Ivančič et al 2018).…”

Geochemical and Mineralogical Approaches in Unraveling Paleoweathering, Provenance, and Tectonic Setting of the Clastic Sedimentary Succession (Western Central Paratethys)

“…The origin from the recycled orogen fits well with the origin of the sediments in the collision zone, which corresponds to the origin from the Alps. The active Europe convergence throughout the Oligocene and Miocene [106] could lead to the sediments originating from the uplifted Dinaric and Southern Alpine blocks such that most of the sediments could be derived from the locally uplifted blocks of the Southern Alps [38,107] to the north and the Dinarides to the south of the Tunjice Hills. Considering that the Central Paratethys covered the area south of the Tunjice Hills in the Early and Middle Miocene [38] and that the lowlands with Quaternary sediments to the east still exist [88,108], the origin from the eastern side is minimal.…”

“…In addition, various tectonic processes influenced the development of the studied area from the Miocene onwards, starting with the collision of the Adriatic and European lithospheric plates, which caused the Alpine orogen, the continental escape of the Eastern Alps, thrusting and folding of the Dinarides, and the syn-rift and post-rift Miocene extensions [20,35,36]. These processes significantly influenced the evolution of faults and the fault system, which in turn affected the evolution of the environment and sediments [37][38][39].…”

On the origin and diversification of the stygobiotic freshwater snail genus Hauffenia (Caenogastropoda: Hydrobiidae) with special focus on the northern species and the description of two new species

“…Hauffenia probably had a Dinaric origin and spread northwards in the Upper Miocene about 10 Ma, when the Pannonian Sea had formed as an isolated continental lake, a remnant of the Paratethys, after the closure of the straits towards Bavaria, Đerdap Valley, Preševo Valley, and Slovenia (Kázmér 1990;Magyar et al 1999). Especially closing the Slovenian strait (Ivančič et al 2018) 1928)], the ancestral populations likely dwelled in karstic and cave conduits (Falniowski & Szarowska 2015). The Pannonian Sea gradually shrunk in surface and the salinity dropped due to discharge of larger rivers and alluvial deposits from the north.…”