A new stratigraphic standard for the open lacustrine to deltaic Pannonian Stage is emerging from the combined sedimentological, lithostratigraphical, sequence stratigraphical, biostratigraphical, seismic stratigraphical, geochronological, and magnetostratigraphical investigations of 6 long drill cores. These were drilled by Paks II Nuclear Power Plant Plc. as a preparatory step for the construction of a new power plant near the city of Paks, Central Pannonian Basin, between 2015 and 2016. The boreholes are in a distance of 8-12 km from each other, and five of them fully penetrated the local Pannonian sequence in a thickness of 390 to 662 m. Each core includes offshore clay marl deposited far from sediment entry points (Endrőd Fm), heterolithic, sandy siltstones of a <200 m high shelf-margin slope (Algyő Fm), and several stacked deltaic deposits from prodelta silts to sandy mouth bars, heterolithics, lignite and sandy channel-fills of the delta plain (Újfalu Fm). Magnetostratigraphic investigations from two cores and authigenic 10Be/9Be dating from two others were combined by means of seismic correlation between the boreholes, and thus they provide a solid geochronological and chronostratigraphic basis for the interpretation of the sedimentologial and paleontological records of the cores. The continuous representation of the earliest Pannonian (11.6–9.1 Ma) in the cores needs further investigation, as neither magnetostratigraphy nor authigenic 10Be/9Be dating gave reliable age data from the basal, condensed calcareous marls. The 9.1 to 6.5 Ma interval, however, is represented in the cores by various lithologies and abundant and sometimes excellently preserved fossils. In the deltaic succession, 8 sedimentary sequences were correlated between the cores; as their duration is not more than 400 kyr each, they can be regarded as 4th-order sequences. The paleontological record of the cores shows a very good agreement with the formerly established biochronostratigraphical system. The cores provide an insight into the evolution of the sedimentary environment and the biota of Lake Pannon between 9.1 and 6.5 Ma with a so far unprecedented temporal and spatial resolution.
The Neogene Transylvanian Basin (TB), enclosed between the eastern and southern Carpathians and the Apuseni Mountains in Romania, is a significant natural gas province with a long production history. In order to improve the (bio) stratigraphic resolution, correlations and dating in the several 100-m-thick upper Miocene (Pannonian) succession of the basin, the largest and most fossiliferous outcrop at Guşteriţa (northeastern part of Sibiu) was investigated and set as a reference section for the Congeria banatica zone in the entire TB. Grey, laminated and massive silty marl, deposited in the deep-water environment of Lake Pannon, was exposed in the ~55-m-high outcrop. The uppermost 25 m of the section was sampled in high resolution (sampling per metres) for macro- and microfossils, including palynology; for authigenic 10Be/9Be dating and for magnetostratigraphy; in addition, macrofossils and samples for authigenic 10Be/9Be isotopic measurements were collected from the lower part of the section as well. The studied sedimentary record belongs to the profundal C. banatica mollusc assemblage zone. The upper 25 m can be correlated to the Hemicytheria tenuistriata and Propontoniella candeo ostracod biozones, the uppermost part of the Spiniferites oblongus, the entire Pontiadinium pecsvaradense and the lowermost part of the Spiniferites hennersdorfensis organic-walled microplankton zones. All samples contained endemic Pannonian calcareous nannofossils, representing the Noelaerhabdus bozinovicae zone. Nine samples were analysed for authigenic 10Be/9Be isotopic measurements. The calculated age data of six samples provided a weighted mean value of 10.42 ± 0.39 Ma. However, three samples within the section exhibited higher isotopic ratios and yielded younger apparent ages. A nearly twofold change in the initial 10Be/9Be ratio is a possible reason for the higher measured isotopic ratios of these samples. Magnetostratigraphic samples showed normal polarity for the entire upper part of the outcrop and can be correlated with the C5n.2n polarity chron (11.056–9.984 Ma, ATNTS2012), which is in agreement with the biostratigraphic data. Based on these newly obtained data and correlation of the biozones with other parts of the Pannonian Basin System, the Guşteriţa section represents the ~ 11.0–10.5 Ma interval, and it is a key section for correlation of mollusc, ostracod, dinoflagellate and calcareous nannoplankton biostratigraphic records within this time interval.
A Balaton-környéki fúrások, feltárások és a nagyfelbontású vízi szeizmikus szelvények által leképezett üledékek közötti rétegtani korreláció közel 30 éve képezi kutatások tárgyát. A parti és víz alatti rétegsor illesztésére elsőként Sacchi et al. (1998, 1999) adtak korrelációs javaslatot, amely szerint a Tihanyi‑félsziget kovás, édesvízi mészkövei (Lóczy (1913) gejzíritjei) a Balaton alatt is megtalálhatók, és ott mint jellegzetesen nagy amplitúdójú reflexiókkal határolt buckás alakzatok ismerhetők fel. A szeizmikus szelvényeken a buckás alakzatok által kijelölt felszínt egy harmadrendű pannóniai szekvenciahatárként (Pan-2) értelmezték. A fenti értelmezés ellenőrzésére mederfúrást végeztünk a Balaton keleti medencéjében, és magmintát vettünk a kérdéses rétegtani szintben elhelyezkedő egyik buckából, és néhány méter vastagságban az alatta lévő rétegekből. A fúrás a tihanyi Fehérpart rétegeihez hasonló, agyagos-homokos képződményeket harántolt, vagyis nem támasztja alá Sacchi et al. (1999) felvetését. Az agyagos képződményekből álló buckákat szeizmikus geometriájuk tükrében olyan csuszamlási szerkezetekként értelmezzük, melyek a területet feltöltő progradáló deltalebenyek előterében keletkeztek, mintegy 8,4‑8,7 millió éve a Lymnocardium decorum biokronban. A fúrómagon végzett természetes gamma-intenzitás, mágneses szuszceptibilitás mérések és üledékföldtani vizsgálatok eredményeit a vízi szeizmikus szelvényekkel összevetetve sikerült azonosítani a csuszamlásos szerkezetek talpát is. Ez a szeizmikus felület egy molluszka-töredékekkel és centiméteres üledékes deformációkkal jellemezhető réteg, amelyhez a természetes gamma- és a mágneses szuszceptibilitás szelvényekben is észlelhető változás társul. A fúrás harántolta a Pan-2 horizontot is, amely a rétegsorban a mélyebben fekvő homokos és a rátelepülő agyagos képződmények éles határaként jelentkezik. E határ alatti üledékek a Be-izotópos koradatok és reverz mágneses polaritásuk alapján a C4Ar (9,1-9,8 Ma) kronban keletkezhettek, tehát úgy tűnik sokkal idősebbek, mint a korábban Horváth et al. (2010) által becsült 7,9 millió év.
Sedimentary successions exposed at basin margins as a result of late-stage inversion, uplift and erosion usually represent only a limited portion of the entire basin fill; thus, they are highly incomplete records of basin evolution. Small satellite basins, however, might have the potential of recording more complete histories. The late Miocene sedimentary history of the Șimleu Basin, a north-eastern satellite of the vast Pannonian Basin, was investigated through the study of large outcrops and correlative well-logs. A full transgressive–regressive cycle is reconstructed, which formed within a ca. 1 million-year time frame (10.6–9.6 Ma). The transgressive phase is represented by coarse-grained deltas overlain by deep-water lacustrine marls. Onset of the regressive phase is indicated by sandy turbidite lobes and channels, followed by slope shales, and topped by stacked deltaic lobes and fluvial deposits. The deep- to shallow-water sedimentary facies are similar to those deposited in the central, deep part of the Pannonian Basin. The Șimleu Basin is thus a close and almost complete outcrop analogue of the Pannonian Basin’s lacustrine sedimentary record known mainly from subsurface data, such as well-logs, cores and seismic sections from the basin interior. This study demonstrates that deposits of small satellite basins may reflect the whole sequence of processes that shaped the major basin, although at a smaller spatial and temporal scale.
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).
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