In the Middle Miocene the area of present-day eastern Slovenia was situated at the eastern mouth of the Slovenian Corridor – a hypothetical seaway connecting the Central Paratethys and the ...Mediterranean. The exact location and time of closure of a seaway between the two neighbouring marine realms are still a matter of debate. We studied Badenian (late Langhian and early Serravallian) calcareous nannoplankton assemblages from eastern Slovenia for their palaeogeographical significance by comparing them to contemporaneous Central Paratethyan and Mediterranean assemblages and the assemblages described in selected ODP and IODP reports. Assemblage composition and the sequence of biostratigraphic events observed in Slovenia were very similar to that in several Mediterranean sites. Comparison with the World Ocean suggests that this similarity reflects communication between the Mediterranean and Paratethyan populations rather than a universal trend of nannoplankton evolution.
Late Badenian assemblages from different localities within the Central Paratethys exhibit considerable variation with respect to the presence of discoasters (considered as typical of the Mediterranean) and the presence of Rhabdosphaera poculi and Hayella challengeri (considered as typical of the Eastern Paratethys). Our results suggest the mixing of Mediterranean and Eastern Paratethyan influences throughout the entire Central Paratethys during the late Badenian. The observed variability explains how opposing views on the status of the marine connection between the Central Paratethys and the Mediterranean in the late Badenian can arise from palaeontological studies of fossil assemblages considering only a single site or a small area.
The gastropod species Pereiraea gervaisi migrated from the Mediterranean to the Central Paratethys – where it is only known from the immediate proximity of the hypothesised Slovenian Corridor. This supports the thesis that the communication between the two seas took place via the Slovenian Corridor and not some other marine connection like the hypothetical Axios (Vardar) Trench.
•Did the Central Paratethys and the Mediterranean communicate in early Serravallian?•Paleontological evidence from eastern Slovenia (C. Paratethys) suggests that they did.•P. gervaisi distribution in Central Paratethys indicates site of marine connection.•Contradictions in previous works result from considering single sites only.
A quick and inexpensive method to determine absolute nannofossil abundance in deep sea sediments – the “drop” technique (modified dilution method) – was compared to two other available methods – the ...filtration and random settling techniques. All techniques rely on the same basic principle, under which a volume of known concentration (bulk sediment weight/mL) is distributed evenly over a known total area (glass slide or filter) to then count particles within a set of (randomly) selected fields of view. The three preparation techniques were also calibrated by spiking the samples with microbeads to approach the “real values” as closely as possible. Significant offsets in abundance estimates between methods mainly reflect bias due to the uneven distribution and/or loss of particles. We show that the drop technique is most consistent and accurate in estimating “real values” and offers similar or better reproducibility than the other techniques. The drop method also allows detection of the same trends with or without calibration with microbeads. The filtration method holds the risk to drastically underestimate absolute abundances, while the settling technique is demanding in terms of time and may suffer from advection processes. The composition of nannofossil assemblages can be reliably determined by any of the three different techniques.
Une méthode rapide et peu onéreuse permettant d’estimer la concentration de nanofossiles dans les sédiments marins profonds – appelée ici la technique de la goutte (la méthode par dilution modifiée) – a été comparée aux deux autres méthodes disponibles – les techniques de filtration et de décantation aléatoire. Toutes les techniques reposent sur le même principe de base, selon lequel un volume de concentration connue (sédiment total poids/volume) est distribué uniformément sur une surface totale connue (lame de verre ou filtre) afin d’ensuite compter les particules dans un ensemble de champs d’observations sélectionnés aléatoirement. Les trois techniques de préparation sont aussi calibrées en ajoutant des microbilles à l’échantillon d’approcher le plus près possible des « valeurs réelles ». Les écarts significatifs de concentration entre les méthodes reflètent principalement le biais lié à des distributions non uniformes et/ou des pertes de particules. Nous montrons que la technique de la goutte est plus consistante et plus précise pour l’estimation de « valeurs réelles ». Elle offre aussi une répétabilité identique, voire meilleure que les autres techniques. La méthode de la goutte permet également la détection de la même tendance avec ou sans calibrage. La méthode par filtration présente le risque de sous-estimer drastiquement les abondances absolues, tandis que la technique par décantation est coûteuse en termes de temps et peut être perturbée par les processus d’advection. La composition des assemblages de nannofossiles est déterminée de façon fiable par chacune des trois techniques différentes.
Rich calcareous nannoplankton assemblages were recovered from the Badenian (Middle Miocene) in Slovenske gorice (Eastern Slovenia). Paleogeographically, the investigated area belonged to the Mura ...Depression, a heterogenous marginal basin of the Central Paratethys. Over one hundred species of calcareous nannoplankton were found in the Badenian marls, among them two new Pontosphaera species were determined and are described in this paper. The nannoplankton assemblages, containing specimens of Pontosphaera geminipora n. sp. and Pontosphaera desuetoidea n. sp., allow their assignment to the standard nannoplankton biozone NN5. Both species are rare and occur in diverse assemblages, indicating warm and stable, relatively deep and oligotrophic depositional environments.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
During a stratigraphic survey of an Early Miocene sedimentary sequence outcropping in SE Slovenia an unusual enrichment of the calcareous nannoplankton assemblage with pentaliths – pentagonal ...nannoliths consisting of five crystal units and showing radial symmetry – was detected. Pentaliths were only abundant in a short interval, which was sampled in detail. The lithological composition of this interval was indistinguishable from that of the underlying and the overlying strata. The composition of nannoplankton assemblages and distribution patterns of different taxa were studied. Mineral composition, total calcite content and
δ
13C values of chosen sediment samples were analysed as well. The pentalith-enriched strata were deposited in the lower Early Miocene, corresponding to the Egerian stage of the Central Paratethys and the Aquitanian of the Mediterranean, in the Slovenian Corridor — a seaway linking the Central Paratethys and the Mediterranean. The presence of rare specimens of
Discoaster druggii and
Helicosphaera carteri allows stratigraphic correlation with the transition of NN1 —
Triquetrorhabdulus carinatus Zone and NN2 —
Discoaster druggii Zone of Martini Martini, E., 1971. Standard Tertiary and Quarternary calcareous nannoplankton zonation. In: Farinacci, A. (Ed.), Proceedings of the II Planctonic Conference, Roma, 1970, Ed. Technoscienza, pp. 739–785. Pentaliths belong to two species:
Braarudosphaera bigelowii and
Micrantholithus vesper. Both species display a wide range of morphological variation and most likely represent a group of sibling species. The pattern of distribution of both species displays obvious similarities throughout most of the studied interval. In the upper part of the studied interval
B. bigelowii reaches maximum abundance, while
M. vesper disappears. Since the ability of
B. bigelowii to thrive in hyposaline water is well known, it appears that
M. vesper tolerates reduced water salinity as well, but to a lesser extent than
B. bigelowii. No significant paleoclimatic and paleogeographical changes are known in this particular region during the Early Miocene, however, the onset of far reaching extensional tectonic processes took place during this time. The enrichment of nannoplankton assemblage with pentaliths may represent a reflection of a short-lived episode of hyposaline conditions. Enhanced influx of freshwater and terrigenous material is indicated by a drop in
13C values, a rise in nannoplankton productivity and the presence of sand in some samples from the pentalith-enriched strata. The most likely causes of this episode are regional tectonic changes, associated with the onset of intensive tectonic activity in the western part of the Central Paratethys.
The article presents a cast fossil of a cephalopod found in sandy limestones (packstones) of Eocene age nearGrdoselo in Central Istria. The phragmocone remains most probably belong to the nautilid ...species Eutrephoceras(Simplicioceras) centrale (Sowerby, 1812). We have determined the age of the fossil with calcareous nannoplankton.The nannofossil assemblage is typical of the Middle Eocene and allows the assignment to the biozone NP15(Nannotethrina fulgens) of the Middle Eocene.
The article discusses fossil porgy fish teeth found in Middle Miocene (Badenian) sandy marl from Mastni hrib near Škocjan in Dolenjska. The teeth belong to the species Pagrus cinctus (Agassiz, 1836) ...and represent the first find in the Krka basin. In sediments of the Central Paratethys and the Mediterranean, the fossil remains of porgy fish are relatively common.
The article discusses a vertebra and a small shark tooth found in the Miocene Govce sandstone near Govce west of Laško in central Slovenia. The vertebra belongs to a shark of the superorder ...Galeomorphii but we could not determine it with greater precision. The small tooth was assigned to Carcharias cf. taurus Rafinesque, 1810. The nannofossils in the sample are scarce and did not allow dating at biozone precision.
The article discusses the first find of an inarticulate brachiopod in Slovenia. The fossil was discovered in Miocenebeds in Badenian sandy and marly limestones outcropping in the Plesko quarry near ...Trbovlje. It belongs to thespecies Lingula dregeri Andreae, 1893.
Presented and discussed are remains of Middle Miocene – Badenian annelids in limestone fragments that consistmostly of tubular-rodlike annelids and lithothamnions. Segmented limestone tubules are ...largely fragmented andfilled with calcite. By their morphology and size they are comparable to polychaetes of the Serpulidae family. Tubularremains could be attributed to genera Protula, Hydroides or Vermiliopsis? The samples of annelidic limestonewith polychaetes were found in environs of Zgornja Pohanca near Kr{ko in eastern part of central Slovenia.
In the paper relatively modestly preserved but very numerous pteropod remains from Middle Miocene – Badenianmicaceous marlstones of Poli~ki Vrh locality in Slovenske gorice, northeastern part of ...Slovenia are described.The fossils were attributed to the pteropod family Cliidae Jeffreys, 1869, respectively the species Clio pedemontana(Mayer, 1868). They represent the first documented finds of this species in Slovenia, and so far also the southernmostoccurrence of the pteropods belonging to this species in Neogene beds of the Styrian basin in the Central Paratethys.
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