Mineral and Chemical Composition of Rudist Valves from Upper Cretaceous Limestones of Southern Istria, Croatia

Turonian to late Santonian limestones of southern Istria are rich in rudist remains. The main aim of this study was to determine the mineral and chemical composition of 22 samples of rudist valves belonging to the genera Durania, Praeradiolites, Radiolites, Gorjanovicia and Vaccinites, and to explain any observed differences. X-ray diffraction and chemical analyses showed that in all the analysed samples, the primary constituents of rudist shells, aragonite and low-Mg calcite, were transformed into diagenetic low-Mg calcite. The strontium concentrations of all the analysed shells correspond to pelagic bulk rock samples altered by diagenesis and are significantly lower than those for biological calcite. Observed differences in the chemical composition of diagenetically altered rudist shells belonging to different rudist genera, namely a slightly higher content of Sr in specimens of Gorjanovicia and Durania and lower concentrations of Mg in shells of Vaccinites are most probably the result of different shell structures and original mineral constituents

Discriminant Function Analysis of Miocene Volcaniclastic Rocks from North-Western Croatia Based on Geochemical Data

Preliminary results of discriminant function analysis of geochemical data of Miocene volcanic and volcaniclastic rocks revealed that it is possible to distinguish rocks of different ages, namely Egerian-Eggenburgian, Karpatian and Badenian. On the basis of calculated coefficients of classification functions, presented in the paper, it is possible to indicate the age of Miocene volcanic and volcaniclastic rocks if their trace element content is known. The analysis also showed that, especially in the case of volcaniclastic rocks, the mineral and petrological composition of the rocks should also be considered. Most of the investigated volcaniclastic rocks from the Mozdjenec and Kalnik areas, the age of which was unknown, are, according to discriminant function analysis, of Egerian-Eggenburgian age

Jabuka Shoal, a New Location with Igneous Rocks in the Adriatic Sea

Petrographic and XRF analyses of the magmatic rock from Jabuka Shoal, 2300 m west of Jabuka Islet (central Adriatic Sea) revealed that the rock is gabbro. This new location of magmatic rocks in the Adriatic confirms their linear arrangement, and indicates the presence of an important fault line which predisposed the occurrences of magmatic rocks

Impressions of the Biota Associated With Waterfalls and Cascades from a Holocene Tufa in the Zrmanja River Canyon, Croatia

The following types of calcified deposits characterize Holocene waterfall tufas in the Zrmanja river: mossy deposits, algally laminated crusts and algally coated grains. Petrological examination revealed, that abundant organic remains belonging to mosses and algae provide supporting material, over which tufa accretion takes place, leaving well-defined impressions of the biota. Postgenetic features like meniscus, isopachous and drusy mosaic calcite spar cementation, as well as aggradational neomorphism are only rarely present

Discovery of Blueschists in the Medvednica Mountain (Northern Croatia) and Their Significance for the Interpretation of the Geotectonic Evolution of the Area

Blueschists were discovered in the metamorphic rocks of the Medvednica mountain. Two varieties of blueschists are recognised, one with garnets and another with omphacite. Determined mineral associations are composed of sodic amphibole (glaucophane and crossite), garnet, omphacite and white mica. These mineral associations indicate metamorphic conditions which are transitional between blueschist and eclogite facies, i.e. high pressures at relatively moderate temperatures (LG, HP/LT). Such conditions are often characteristic of subduction zones. The occurrence of high-pressure metamorphic rocks in the Medvednica mountain, together with local outcrops of ultramafic rocks (serpentinised harzburgite, dunite and serpentinite) indicate subduction related rocks of the Dinaric part of the Tethyan oceanic crust. In the northern part of the Dinarides, ultramafic rocks and glaucophane schists have also been found in the Motajica and Fruska gora mountains. The Medvednica-Motajica-Fruska gora zone probably represents a relict subduction zone in the Dinaridic part of Tethys, along which regional high-pressure metamorphism took place

Upper Cretaceous-Palaeogene Tholeiitic Basalts of the Southern Margin of the Pannonian Basin: Pozeska gora Mt. (Croatia)

According to the geological relationships in the region of Pozeska gora Mt. (the southern margin of the Pannonian Basin, northern Croatia), basic eruptive rocks are considered to be of Upper Cretaceous-Palaeogene age. Detailed petrographic examination, based on physiographic description, the chemical composition of major and trace elements, rare earth elements and stable isotopes, indicates that these primary tholeiitic basalts have variable structural-textural characteristics, and were postmagmatically affected by metamorphic processes. Tholeiitic basalts originated from the upper mantle, and were placed in the form of subaquatic effusions in the extensional zones within continental crust

Paleogeographic evolution of the Southern Pannonian Basin: 40Ar/39Ar age constraints on the Miocene continental series of notthern Croatia

The Pannonian Basin, originating during the Early Miocene, is a large extensional basin incorporated between Alpine, Carpathian and Dinaride fold-thrust belts. Back-arc extensional tectonics triggered deposition of up to 500-m-thick continental fluvio-lacustrine deposits distributed in numerous sub-basins of the Southern Pannonian Basin. Extensive andesitic and dacitic volcanism accompanied the syn-rift deposition and caused a number of pyroclastic intercalations. Here, we analyze two volcanic ash layers located at the base and top of the continental series. The lowermost ash from Mt. Kalnik yielded an 40Ar/39Ar age of 18.07 ± 0.07 Ma. This indicates that the marine-continental transition in the Slovenia-Zagorje Basin, coinciding with the onset of rifting tectonics in the Southern Pannonian Basin, occurs roughly at the Eggenburgian/ Ottnangian boundary of the regional Paratethys time scale. This age proves the synchronicity of initial rifting in the Southern Pannonian Basin with the beginning of sedimentation in the Dinaride Lake System. Beside geodynamic evolution, the two regions also share a biotic evolutionary history: both belong to the same ecoregion, which we designate here as the Illyrian Bioprovince. The youngest volcanic ash level is sampled at the Glina and Karlovac sub-depressions, and both sites yield the same 40Ar/39Ar age of 15.91 ± 0.06 and 16.03 ± 0.06 Ma, respectively. This indicates that lacustrine sedimentation in the Southern Pannonian Basin continued at least until the earliest Badenian. The present results provide not only important bench marks on duration of initial synrift in the Pannonian Basin System, but also deliver substantial backbone data for paleogeographic reconstructions in Central and Southeastern Europe around the Early–Middle Miocene transition

Discovery of Blueschists in the Medvednica Mountain (Northern Croatia) and Their Significance for the Interpretation of the Geotectonic Evolution of the Area

Blueschists were discovered in the metamorphic rocks of the Medvednica mountain. Two varieties of blueschists are recognised, one with garnets and another with omphacite. Determined mineral associations are composed of sodic amphibole (glaucophane and crossite), garnet, omphacite and white mica. These mineral associations indicate metamorphic conditions which are transitional between blueschist and eclogite facies, i.e. high pressures at relatively moderate temperatures (LG, HP/LT). Such conditions are often characteristic of subduction zones. The occurrence of high-pressure metamorphic rocks in the Medvednica mountain, together with local outcrops of ultramafic rocks (serpentinised harzburgite, dunite and serpentinite) indicate subduction related rocks of the Dinaric part of the Tethyan oceanic crust. In the northern part of the Dinarides, ultramafic rocks and glaucophane schists have also been found in the Motajica and Fruska gora mountains. The Medvednica-Motajica-Fruska gora zone probably represents a relict subduction zone in the Dinaridic part of Tethys, along which regional high-pressure metamorphism took place

Immobilisation of Acinetobacter calcoaceticus using natural carriers

There is a growing interest to immobilize desired bacteria using inexpensive materials in order to improve the wastewater treatment process. Three different types of carriers namely natural zeolite, magnesium-exchanged natural zeolite and quartz sand of different particle size were used to immobilize the phosphate-accumulating bacteria Acinetobacter calcoaceticus and to determine which one was the most effective. Bacteria were cultured for 24 h in various reactors containing different particle sizes of each of the carriers. The majority of the cultured bacterial population was immobilised onto the different carriers by means of adsorptive growth while a minority of free cells was observed in the supernatant. The number of immobilised viable cells (CFU) depended on the type of carrier and the particle size. The highest loading rate of immobilised cells (68.61±1.11 x 108 CFU/g) was observed with the smallest particle size ( Water SA Vol. 31 (2) 2005: pp.261-26