Zlatan Bajraktarević

Benthic Foraminiferal Assemblages in a Restricted Environment - An Example from the Mljet Lakes (Adriatic Sea, Croatia)

Benthic foraminiferal assemblages from a peculiar restricted marine environment, the Mljet Lakes (Mljet Island, Adriatic Sea, Croatia) have been studied. These lakes are drowned karst dolines, which are connected with the Adriatic Sea through a narrow, shallow channel. Occasional stagnant conditions in the marine lakes cause hypoxic and anoxic conditions in the bottom waters. Such stressed conditions are reflected in oligospecific benthic foraminiferal assemblages with a Shannon-Wiener species diversity index (H) ranging from 0.8 to 1.0 and equitability index (E) ranging from 0.18 to 0.26, identified in samples from each marine lake. In the more dysoxic Malo Jezero, Haynesina depressula dominates an assemblage of 12 benthic foraminiferal species. In the less (and less frequently) hypoxic Veliko Jezero, we found an Asterigerinata mamilla a s s e m b l a g e with 18 foraminiferal species. A more diverse assemblage containing 55 different benthic foraminiferal species occupies an adjacent opensea station. Long-term salinity measurements indicate that H. depressula tolerates higher salinity than formerly presumed (up to 38 ‰), and is well adapted to stressed hypoxic conditions.

FIRST RECORD OF DINOSAURS IN THE LATE JURASSIC OF THE ADRIATIC-DINARIDIC CARBONATE PLATFORM (CROATIA)

Abstract All previously known dinosaur remains on the Adriatic-Dinaridic carbonate platform (ADCP) were described from Cretaceous deposits. A new trackbearing locality is late Tithonian in age and represents the oldest evidence of dinosaurs on the ADCP. The site is in an active quarry near the village of Kirmenjak in western Istria. Almost a thousand sauropod footprints including 23 single trackways have been found on the outcrop. Oval impressions represent pes prints, and horseshoe-shaped impressions represent manus prints; pes prints are 23 to 52 cm long. Calculated heights at the hip range from 153 to 306 cm. The main direction of dinosaur movement was toward the northeast, and some of the individuals were moving together. The trackways show a characteristic narrow gauge, and pace and stride lengths indicate a slow walk. The footprints are similar to Parabrontopodus ichnogenus, and the ichnocoenosis could be assigned to the Brontopodus ichnofacies. The presence of the sauropods on the Adriatic-Dinaridic carbonate platform during the Late Jurassic could be explained by connection with the African continent via its southern margins during emersion.

Stratigraphy and Palaeogeography of Miocene Deposits from the Marginal Area of Žumberak Mt. and the Samoborsko Gorje Mts. (Northwestern Croatia)

Miocene sediments rimming the Palaeozoic–Mesozoic–Palaeogene rocks, form Žumberak Mt. and the Samoborsko Gorje Mts. Spatial analysis of the setting and development of the surface Miocene stratigraphy, at the marginal areas of the Žumberak and Samoborsko Gorje Mts., allows four palaeogeographic areas to be distinguished: Žumberak, Plesivica–Sveta Jana, Samobor–Sveta Nedelja and Grdanjci. In the Miocene deposits (totaling 350 m), within the area of Žumberak, coarse-grained clastics from deltaic deposits of Pannonian age prevail. Here only, 50 m of sediments of Pliocene–Pleistocene age overlie the Miocene deposits whereas Mesozoic carbonates represent the basement. The Plesivica–Sveta Jana area is characterized by a 600 m sequence of Miocene deposits, mainly overlying Triassic dolomites, where finely-grained layers of marls and silts prevail. In this area, Miocene successions from the Badenian to the Pontian are characterized by a continuity of sedimentation with an inherited depositional environment. In the area of Samobor–Sveta Nedelja, the basement is diverse: Triassic dolomites, volcanogenic–sedimentary complex of Cretaceous age and a clastic–carbonate complex of Palaeogene age. The Miocene succession shows a regressive trend from the Badenian to the Pontian and the total thickness is estimated at 400 m. The area of Grdanjci differs considerably from the other Miocene palaeorelief. An approximately 50 m-thick series of coarsegrained clastics with coal is distinguished, of unclear stratigraphic age (Ottnangian?). Miocene sediments of the Grdanjci area are represented by both a transgressive type of conglomerates and shallow water limestones of Badenian age, with a total thickness of about 100 m. The development of the Miocene stratigraphy of the Žumberak and Samoborsko Gorje Mts. is generally correlative with that in the other parts of the Pannonian area, though it does exhibit local variations. Comparison of the Miocene palaeorelief of Žumberak Mt. with the Samoborsko Gorje Mts., together with neighbouring areas, enabled wider correlation with other parts of northern Croatia, and the more distant Western and Central Paratethys.

A new dinosaur tracksite in the Late Albian of Istria, Croatia

A new site with dinosaur footprints has been found in the upper Albian sediments of Istria, Croatia. The site was discovered near the city of Pula, at the Zlatne Stijene locality. The carbonate succession of the Zlatne Stijene locality is characterized by thin bedded limestones deposited in peritidal and foreshore environments. The microfossil assemblage found at the site indicates a late Albian age. One clearly distinguishable footprint and four indeterminate rounded tracks were discovered at the investigated outcrop. The footprint is tridactyl and belongs to a medium-sized bipedal theropod dinosaur of approximately 3 meter in length. Regarding dimensions and morphology it is closely related to the other late Albian theropod footprints from the Adriatic-Dinaridic carbonate platform (ADCP). The Zlatne Stijene locality fits with the Brontopodus ichnofacies concept.

Environmental changes in the lower Mirna River valley (Istria, Croatia) during Upper Holocene

Sedimentological, macro- and micropaleontological analyses on 3 hand augering cores were carried out in the terminal sector of the Mirna River, in order to study the depositional facies and the environmental evolution. The cores allowed investigating the subsoil down to 13 m of depth, sampling a fairly continuous depositional sequence of estuarine, lagoon and alluvial sediments. The Holocene marine transgression entered upstream the present-day coast for at least 8 km, while in the last 7 ka it was followed by the progradation of Mirna delta. The protected coast offered by the lower valley and the strong input of fresh water led to the presence of a brackish microfauna even in front of the river mouth. The oldest sediments in the cores were characterized by dominance of Ammonia beccarii and significant proportions of Elphidium spp. and miliolids suggesting estuarine origin. Foraminiferal assemblage in overlying sediments became less diverse, relative abundance of Elphidium spp. and miliolids dropped, implying shift to transitional environment (inner lagoon facies, Bb). Sediments originating in hyposaline marshes (facies Ba) had the lowest foraminiferal species diversity index (A. beccarii predominated over Trochammina inflata and Haynesina sp.) Since late-Antiquity a significant alluvial matter input led to the deposition of several meters of silty clay sediments that in the core M3 are thicker than 9 m. The sedimentary supply has been partly increased by deforestation carried out in the Mirna catchment area that was particularly severe from the 15th to the 19th century and fed the fluvial system with large amount of material, allowing the fast progradation of the delta. This study highlights the potential role of the use of hand augering in sampling and describing the subsoil in reconstructing the geomorphological evolution of the area and supporting the study of past relative sea levels, climate changes, and anthropogenic activities that occurred during the Holocene.

Dinosaur footprints in the Upper Hauterivian deposits of the Palud Bay in Istria, Croatia

Sixteen dinosaur footprints are exposed along the upper-bedding plane of a single Upper Hauterivian limestone layer in the Palud bay (western Istria, Croatia). This distinct footprint-bearing horizon is part of the thick Mesozoic Adriatic-Dinaridic Carbonate Platform stratal succession. Strata at the Palud site are characterized by peritidal (shallow subtidal to intertidal) limestone with several shallowing-upward cycles composed of mudstone, peloidal wackestone/packstone, peloidal packstone/grainstone and fenestral mudstone/wackestone with common geopetal infill. The Late Hauterivian age of these deposits is determined from their microfossil assemblage, which is dominated by ostracods, benthic foraminifera and calcareous green algae Dasycladales. The Palud site dinosaur footprints are circular to elliptical in shape, with no clearly visible digit impressions (except for one questionable example), and are rather large with average length of 30 cm. Most footprints have a well-defined expulsion rim that represents displacement and compression of soft, waterlogged sediment substrate by the weight of the dinosaur. All of the footprints are of nearly same shape and size, which indicates that they were produced by the same kind of tracemaker – likely a sauropod dinosaur. These animals left their footprints on top of a shallowing-upward succession of an intertidal environment during a short subaerial exposure of fine-grained carbonate sediment.