Paleontoloski Institute Ivana Rakovca ZRC SAZU

Ljubljana, Slovenia

Paleontoloski Institute Ivana Rakovca ZRC SAZU

Ljubljana, Slovenia
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Mikuz V.,University of Ljubljana | Bartol M.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Soster A.,Visnja vas 9
Geologija | Year: 2014

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.

Mikuz V.,University of Ljubljana | Bartol M.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Ulaga S.,Log 15a
Geologija | Year: 2014

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.

Segvic B.,University of Geneva | Kukoc D.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Dragicevic I.,University of Zagreb | Vranjkovic A.,University of Zagreb | And 4 more authors.
Ofioliti | Year: 2014

Within the ophiolitic mélange of the Central Dinaridic Ophiolitic Belt (CDOB) that stretches throughout the Balkans region in SE Europe, a latest Bajocian-early Bathonian radiolarian assemblage was obtained from chertrich shaly to silty matrix. The sampling locality in northern Bosnia and Herzegovina is characterized by a highly-diversified ophiolitic suite, consisting of basic and ultrabasic rocks of different geotectonic provenances. This makes the radiolarian dating a convenient complementary tool for studying the geodynamic history of CDOB within a broader regional context. The host sediments and the nature of their associated crystalline rocks suggest that radiolarian deposition occurred relatively close to the Adria shelf margins, predating or being contemporaneous to the rapid transitions in the Dinaridic Neotethys geotectonic setting, changing from active ridge magmatism to an intraoceanic subduction environment and island-arc volcanism. The minimum age of ophiolite mélange formation is defined by the mineral equilibration ages in metamorphic sole (161±4 Ma), with the obduction tectonics that must have lasted at least until the Oxfordian time (i.e. termination of MOR activity in the Dinarides). This age correlates well with the ages of sediments reported elsewhere in the mélange of the Dinaride-Hellenide orogenic system.

O'Dogherty L.,University of Cádiz | Carter E.S.,Portland State University | Gorican S.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Dumitrica P.,Dennigkofenweg 33
Geological Society Special Publication | Year: 2010

This paper summarizes 30 years of research on the biostratigraphy of Triassic radiolarians and presents a correlation of currently-used radiolarian zonations established in North America, Europe, Japan and Far East Russia. An up-to-date stratigraphic distribution of all hitherto described and still valid Triassic genera is provided. This new range chart consists of 282 genera and allows an accurate dating to substage level. It also clearly manifests general trends in radiolarian evolution through the Triassic. The end-Permian extinction, the most severe extinction in the history of radiolarians, was followed by a long recovery until the early Anisian. The middle and late Anisian were then characterized by a rapid explosion of new morphologies. Maximum generic diversity was attained during the early Carnian, but the first severe extinctions also occurred in the Carnian. A progressive decline of diversity took place through the Norian and Rhaetian, and ended in a mass extinction around the Triassic-Jurassic boundary. © The Geological Society of London 2010.

Guex J.,University of Lausanne | O'Dogherty L.,University of Cádiz | Carter E.S.,Portland State University | Gorican S.,PaleontoloSki Institute Ivana Rakovca ZRC SAZU | And 2 more authors.
Geobios | Year: 2012

Radiolarians are Cambrian to recent holoplanktonic marine protists with morphologically very diverse siliceous skeletons. In the Mesozoic, two main groups are differentiated: nassellarians (mostly conical, composed of one or more consecutive segments) and spumellarians s.l. (generally spherical, composed of one or more concentrical shells). Following the extensive radiolarian research over the past decades, it is now possible to trace the development of some Mesozoic radiolarians through time and to reliably reconstruct several phyletic lineages. In this study, we analyse some lineages with well-marked trends in skeletal development and compare these trends with those observed in other marine organisms. The most usual geometrical transformations occurring in radiolarians are characterized by an increase of the surface of the shell. In several nassellarians, we observe a progressive inflation of the test, leading to a spherization. In some groups, such a trend leads to cryptocephalization, a phenomenon analogous to the orbulinization of some Tertiary foraminifers. The development of a terminal tube or of apertural arches is also frequent in the nassellarians. In many respects, the transformations observed in the spumellarians are related to the same kind of geometrical modifications. For example, the addition of an arch to a polar spine in Baumgartneria, of a ring in the Saturnalids, of a button or spine also in the ring of Aurisaturnalis, are clear examples of an increase of the shell surface through time. Proterogenesis is also frequent in nassellarians and spumellarians s.l., especially in the Pyloniaceae and Centrocubidae where new structures first develop in the earliest ontogenetic stage. The initial antapical spicule frequently evolves by doubling or quadrupling of the antapical spine, leading to entirely new modes of growth in subsequent descendants and to forms which are cryptogenic with regard to their ancestors. During extinction crises corresponding to highly stressful periods, radiolarians tend to lose the structures which were developed during their preceding evolution: loss of the ring in the Axoprunids, loss of the twisting of the spines in Tipperella, disappearance of inflated nassellarians in the Early Jurassic, etc. Such losses lead to the reappearance of primitive characters. © 2012.

O'Dogherty L.,University of Cádiz | De Wever P.,French Natural History Museum | Gorican S.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Carter E.S.,Portland State University | Dumitrica P.,Dennigkofenweg 33
Palaeoworld | Year: 2011

The recent systematic and stratigraphic revision of all described Mesozoic radiolarian genera (O'Dogherty et al., 2009a,b,c) represents the state of the art in the taxonomy of this group. Using this information, we have improved the stratigraphy of Mesozoic families by redefining their ranges at the substage precision.Our analysis shows a clear change in faunal composition at the Permo-Triassic boundary (only 15 families cross: 2 Albaillellaria, 4 Latentifistularia, 3 Entactinaria, 2 Nassellaria and 4 Spumellarian) followed by an explosion at the Middle Triassic. Through the Late Triassic, 32 families began to go extinct, leading to a drastic disappearance of typical Triassic morphotypes. However, the Triassic-Jurassic boundary does not record a similar extinction at the family level; 37 families and subfamilies apparently crossed the boundary. Paradoxically, the revision of genera has shown the survival of only 30 genera at this boundary belonging to 23 families. The reason of such a discrepancy is the virtual crossing of 14 families at Triassic-Jurassic boundary. That is, families having representatives in both the Triassic and Jurassic, but without any record close to the boundary.Similarly, these discontinuities in the ranges are observed throughout the Jurassic and Cretaceous, but especially at the Cretaceous-Paleogene boundary, where 21 families are crossing virtually. Among the orders, Entactinaria presents proportionally the highest number of families with discontinuous ranges. The reason could be related to the scarcity of studies on this group whose systematic classification needs a good knowledge of the initial spicule. We analyze in detail the major discontinuities observed in the range of some families. Explanations considering discontinuous fossil record, limited knowledge on phylogenetic relationships, or possible homeomorphism are proposed. © 2010 Elsevier Ltd and Nanjing Institute of Geology and Palaeontology, CAS.

Moix P.,Rue de la Combe 55 | Gorican S.,Paleontoloski Institute Ivana Rakovca ZRC SAZU
Geodinamica Acta | Year: 2013

Two large blocks of red bedded chert identified within the Late Cretaceous-Paleocene Bornova mélange in northern Karaburun Peninsula yielded Jurassic (late Bathonian-early Oxfordian) and Cretaceous (middle-late Albian) radiolarian assemblages. These new data confirm the correlation of the Bornova mélange with the Bornova Flysch Zone (BFZ) and the Izmir-Ankara mélanges. A review of all previously obtained ages in chert blocks of the BFZ and the Izmir-Ankara mélanges is provided in order to strengthen this correlation. © 2014 Taylor & Francis.

Kukoc D.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Gorican S.,Paleontoloski Institute Ivana Rakovca ZRC SAZU | Kosir A.,Paleontoloski Institute Ivana Rakovca ZRC SAZU
Bulletin de la Societe Geologique de France | Year: 2012

In the Bohinj area (NW Slovenia), a distinctive interval of carbonate gravity-flow deposits overlying the pelagic Biancone limestone was analyzed for microfacies and dated with radiolarians. This interval, newly described as the Bohinj Formation, consists of a 3 m thick carbonate breccia capped by a 4 m thick massive calcarenite. The breccia is composed of clasts of carbonate platform facies, isolated ooids and oncoids, and bioclasts of shallow-marine benthos. Intraclasts of pelagic calpionellid wackestone and rare chert clasts are also present. Radiolarians from the pelagic limestone below indicate a latest Tithonian to earliest Berriasian age, and those above indicate a Berriasian to Early Valanginian age. Paleogeographically, the area was part of the Bled basin, which had a relatively distal position on the Adriatic continental margin. This position is suggested by flysch-type deposits in the area that are Early Cretaceous in age and thus correlate with the Bosnian Flysch in the central Dinarides. The Bohinj Formation provides evidence of a carbonate platform that must have been located more internally but is now not preserved. This inferred platform (named the Bohinj Carbonate Platform) may have developed on top of a nappe stack, which formed during the early emplacement of the internal Dinaric units onto the continental margin. The platform correlates regionally with genetically similar isolated carbonate platforms of the Alpine - Dinaride - Carpathian orogenic system, e.g., with the Plassen Carbonate Platform in the Northern Calcareous Alps and the Kurbnesh Carbonate Platform in Albania.

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