Bogdan Jurkovšek

THE LOWER TRIASSIC SHALLOW MARINE SUCCESSION IN GORSKI KOTAR REGION (EXTERNAL DINARIDES, CROATIA): LITHOFACIES AND CONODONT DATING

The paper aims to present Lower Triassic lithofacies definition and first conodont fauna of Gorski Kotar region, Croatia. The depositional environment is envisaged as shallow marine realm of a passive continental margin. Sedimentary complex differentiates in predominantly carbonate sedimentation that characterises the beginning of deposition with upward increasing trend of terrigeneous influx. Lithofacial units have been defined as oolitic bar facies, lagoonal facies, shoreface-offshore facies, ooid-sandy shoal facies, restricted bay facies and flat-pebble conglomerate facies.The following conodont taxa were collected: Ellisonia sp., Foliella gardenae, Hadrodontina sp., Hindeodus parvus, Hindeodus sp., Pachycladina obliqua, ?Parachirognathus sp., Platyvillosus costatus and Pl. hamadai. The oldest strata yield Hindeodus parvus marking lowermost Triassic. The biostratigraphical data enable recognition of the parvus-isarcicella zones, obliqua Zone and Platyvillosus Subzone. The finds of Hindeodus parvus, Platyvillosus costatus and Pl. hamadai represent their first records in the External Dinarides and enable correlation of the Early Triassic conodont faunas of the Western Tethyan realm.

Geology of the Classical Karst Region (SW Slovenia–NE Italy)

ABSTRACT The paper aims to present the geology of the western part of the Classical Karst (NW Dinarides), located at the border between Slovenia and Italy. The work is based on archive, published and new data collected by Slovenian and Italian researchers within several scientific national and Cross Border Cooperation projects. The map, produced at a scale of 1:50,000, summarizes the lithological and structural setting and is supplemented by three geological cross-sections of the study area.

A fossil feather from the Upper Cretaceous of Kras (Slovenia)

Abstract A fossil feather preserved as a carbonised trace is described from the Tomaj Limestone at Križ, in the Kras region of southwestern Slovenia. The Tomaj Limestone is a platy and laminated limestone with cherts, which occurs within a well-bedded rudist limestone of the Santonian–Campanian Lipica Formation. It was deposited in a lagoon environment and has yielded a diverse fossil assemblage. Whether this feather belonged to a bird or to a dinosaur is unclear, but it is an addition to the scanty record of Late Cretaceous feathers, from a palaeobiogeographically interesting area.

CONODONT DATING OF THE LOWER TRIASSIC SEDIMENTARY ROCKS IN THE EXTERNAL DINARIDES (CROATIA AND BOSNIA AND HERZEGOVINA)

Two Lower Triassic sedimentary successions have been dated by means of conodonts in the External Dinarides: Plavno section near Knin, Croatia and Bosansko Grahovo section in Bosnia and Herzegovina. Deposition in both sections shows similar characteristics, differentiated in three continuously deposited facies. The Siliciclastic facies was previously considered Seis beds and assigned to the lower Lower Triassic, the Mudstone facies, and the Siltstone-mudstone facies (occurring in the upper part of the succession) were formerly considered as Campil beds of the upper Lower Triassic. Vertical succession of Siliciclastic, Mudstone, and Siltstone-mudstone facies of both investigated sequences was interpreted as deepening of the environment envisaged as a transgressive trend in a shallow shelf environment. Facies successions at Plavno (690 m thick) and Bosansko Grahovo (229 m thick) differentiate for the presence of Dolostone facies in the lowest part of the Plavno succession. Conodont fauna of Dolostone facies at Plavno section is represented by isarcicellids, Isarcicella staeschei and I. isarcica (sample 3) that marks the Griesbachian isarcica Zone. The Siliciclastic facies of Plavno and Bosansko Grahovo sections is characterized by shallow-water euryhaline taxa attributed to the Smithian, part of the late Dinerian-Smithian obliqua Zone. This fauna is prevailed by Hadrodontina anceps and Pachycladina obliqua with co-occurrence of Smithian Parachirognathus ethingtoni and very rare presence of Foliella sp. or ?Furnishius sp. Discerned conodont taxa enable us to establish conodont zonation which gives new insight to the range of the so-called Siusi and Campil beds.

Rollmarks of Soft Parts and a Possible Crop Content of Late Cretaceous Ammonites from the Slovenian Karst

Rollmarks associated with Placenticeratidae of the Lower Campanian milleri-bidorsatum group are interpreted as prints of their soft parts, possibly of the hyponome, while a cluster of minute brachiopods is interpreted as the crop content of the decaying ammonite.

Paleogeographic significance of Upper Triassic basinal succession of the Tamar Valley, northern Julian Alps (Slovenia)

Abstract The Julian Alps (western Slovenia) structurally belong to the eastern Southern Alps. The Upper Triassic succession mostly consists of shallow water platform carbonates of the Dolomia Principale-Dachstein Limestone system and a deep water succession of the Slovenian Basin outcropping in the southern foothills of the Julian Alps. In addition to the Slovenian Basin, a few other intraplatform basins were present, but they remain poorly researched and virtually ignored in the existing paleogeographic reconstructions of the eastern Southern Alps. Herein, we describe a deepening-upward succession from the Tamar Valley (north-western Slovenia), belonging to the Upper Triassic Tarvisio Basin. The lower, Julian-Tuvalian part of the section comprises peritidal to shallow subtidal carbonates (Conzen Dolomite and Portella Dolomite), and an intermediate carbonate-siliciclastic unit, reflecting increased terrigenous input and storm-influenced deposition (Julian-lowermost Tuvalian shallow-water marlstone and marly limestone of the Tor Formation). Above the drowning unconformity at the top of the Portella Dolomite, Tuvalian well-bedded dolomite with claystone intercalations follows (Carnitza Formation). The latter gradually passes into the uppermost Tuvalian–lowermost Rhaetian bedded dolomite with chert and slump breccias, deposited on a slope and/or at the toe-of-slope (Bača Dolomite). Finally, basinal thin-bedded bituminous limestone and marlstone of Rhaetian age follow (Frauenkogel Formation). The upper part of the Frauenkogel Formation contains meter-scale platform-derived limestone blocks, which are signs of platform progradation. The Tarvisio Basin may have extended as far as the present Santo Stefano di Cadore area, representing a notable paleogeographic unit at the western Neotethys margin.

NEW LADINIAN AMMONOIDS FROM MT. SVILAJA (EXTERNAL DINARIDES, CROATIA)

A small collection of Ladinian ammonoids from Mt. Svilaja (External Dinarides) is here described for the first time. The ammonoids were collected from a thick succession, which yielded in its lower part the classic Lower Triassic ammonoid faunas of Muae, known since the XIX century. The collection comes from an interval yielding conodonts of the hungaricus Assemblage zone, and is composed of leiostraca ( Proarcestes ) and trachyostraca ammonoids. The latter consists of the new genus Alkaites , and the new species A. dinaricus , Detoniceras svilajanus and Argolites trinodosus . Alkaites n. gen. is characterised by involute coiling, v-shaped ventral side and five spiral rows of nodes. D. svilajanus n. sp. is distinguished by flat ventral side, and four rows of nodes with peculiar ratio 1:1:2:2 between perimbilical,1st lateral, 2nd lateral, and ventrolateral nodes. A. trinodosus n. sp. is characterised from any other species of Argolites by three rows of nodes. At the present the new genus Alkaites and the three new species are known only from the study area. The dating of the new taxa is done by indirect correlations based on the distribution of Detoniceras and Argolites in other sections of the Southern Alps, as well as on the calibration of the hungaricus Assemblage zone with the ammonoid standard scale. The inferred age is Gredleri Zone (Lower Ladinian).

Triassic charophytes from Slovenia: palaeogeographic implications

Charophyte gyrogonites are reported for the first time from the Triassic of Slovenia and Southern Europe. They were found associated with Late Ladinian-Early Carnian conodonts in marine limestone of the Oblakov Vrh succession, in the northern part of the Outer Dinarides. The charophyte assemblage consists of rare gyrogonites belonging to genus Stenochara, which would probably have been transported to a marine depositional setting from their growing area, a freshwater or brackish environment located nearby. This confirms that smaller areas of palaeogeographic highs, with non- marine facies, occurred during the Triassic in the Adriatic-Dinaric Carbonate Platform and could be reached by charophytes after long-distance dispersal.

Unusual brachiopod fauna from the Middle Triassic algal meadows of Mt. Svilaja (Outer Dinarides, Croatia)

Abstract. Ladinian deposits at Mt. Svilaja in Dalmatia (Outer Dinarides, Croatia) yielded an abundant brachiopod fauna of low diversity interpreted as a parautochthonous assemblage representing an ecosystem of dasycladacean submarine meadow. The fauna consists of four named species and one left in open nomenclature. The most common is the spiriferinide Flabellocyrtia flabellulum Chorowicz and Termier, 1975 (Spiriferinida) accounting for more than 70% of the material. The athyridide Cassianospira humboldtii (von Klipstein, 1845) is the only species known from elsewhere (Anisian of Southern Alps). The new species of Spiriferinida Thecocyrtella dagysii Halamski, Bitner, Kaim, Kolar-Jurkovšek, and Jurkovšek n. sp. differs from other representatives of the genus in having a deep ventral sulcus. Albasphe albertimagni Halamski, Bitner, Kaim, Kolar-Jurkovšek, and Jurkovšek n. gen. n. sp. is a new brachiopod that possesses a dorsal septum with an intra-septal cavity and dorsal submarginal ridges, both features in common with Aalenian Zellania Moore, 1855 from which it differs in lack of the ventral septum and of ventral submarginal ridges. They are interpreted as members of a sparsely recorded paedomorphic evolutionary line of terebratulides with secondarily lost loop, described formally herein as Gwyniidina Halamski and Bitner n. subordo and subdivided into newly emended Dispheniidae Grant, 1988 (Dispheniinae Grant, 1988 with the only genus Disphenia and Albasphinae Halamski and Bitner n. subfam. with Albasphe and Zellania) and Gwyniidae MacKinnon, 2006 (including Recent Gwynia and Simpliciforma). In contrast to previous interpretations, the trocholophe lophophore of Gwynia is interpreted herein as secondarily simplified.

New record of the inarticulate brachiopod genus Discinisca from the Upper Triassic (Carnian) of the Julian Alps, NW Slovenia

The inarticulate brachiopod genus Discinisca DALL, 1871 has been identified in the Upper Triassic (Carnian) bituminous cherty limestones of the Julian Alps, NW Slovenia that were deposited in an oxygen depleted environment with a high sedimentation rate on an intraplatform basin. The collection represents both ventral and dorsal valves which are relatively large, ornamented by faint radial lines and growth lines. The described here Discinisca cf. zapfei from Slovenia by its delicate radial ornamentation resembles D. zapfei RADWAŃSKI & SUMMESBERGER, 2001 from the Upper Triassic of the Northern Calcareous Alps, Austria, differing in the position of the apex.