International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

Volume 59 no. 3 / June 2008

Volume 59 no. 3 / June 2008

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Articles in this issue

  • Stripped image of the gravity field of the Carpathian-Pannonian region based on the combined interpretation of the CELEBRATION 2000 data

    Abstract: The Carpathian-Pannonian region is one of the areas of Central Europe with good coverage of geophysical and geological data. This is due to its complicated evolution that attracted scientific interest already in the past. In addition, several international seismic experiments were conducted here in the last 10 years. The model to be presented uses most of these available data to perform a combined gravity–seismic interpretation. The analysis of the gravity anomalies is performed in order to identify the sources of the anomalies, separate their effects and localize the lithospheric inhomogeneities. The gravity stripped image of the region reveals significant differences in the nature of the Microplates ALCAPA and Tisza-Dacia from the surrounding regions.
  • The Carnian-Norian basin-platform system of the Martuljek Mountain Group (Julian Alps, Slovenia): progradation of the Dachstein carbonate platform

    Abstract: In the Martuljek Mountain Group (MMG), positioned in the northern part of the Julian Alps (NW Slovenia), a widespread drowning of the middle Carnian carbonate platform is marked by the onset of a thin (approximately 25 m) horizon of reddish pelagic platy basinal limestones (Martuljek platy limestone). According to conodont data, different ages of the upper part of the Martuljek platy limestone are documented, namely late Carnian in the SW and early Norian in the NE part of the MMG. The rimmed Dachstein carbonate platform progrades into the basin with typically developed facies zones: slope and reef margin (approximately 300 m thick) with abundant coral fauna with other framebuilders and the Lofer cyclic Dachstein Limestone in the backreef peritidal area. In the NW face of the Mt Skrlatica, platform to the basin transition is spectacularly exposed. The interfingering of slope to basin sediments and the dip of the clinostratification, indicate SW to NE progradation of the Dachstein platform (in recent orientation), which is also in accordance with conodont data estimation of the underlying Martuljek platy limestones. The margin of the Dachstein platform in the MMG is thus progressively younger from the SW direction to the NE. After (and during) the filling of the basin, the peritidal carbonate platform, with a more than 1 km thick succession of the Dachstein Limestone prevailed until the end of the Triassic Period in the central part of the Julian Alps. The Carnian drowning event in the Julian Alps and also in the Kamnik–Savinja Alps is not just a locally limited phenomenon, as described so far, but a widespread event, triggering the growth of the Tuvalian–Norian reefs, facing more open marine areas.
  • Organic geochemistry of Jurassic-Cretaceous source rocks and oil seeps from the profile across the Adriatic-Dinaric carbonate platform

    Abstract: Organic geochemical and stable isotope investigations were performed to provide an insight into the depositional environments, origin and maturity of the organic matter in Jurassic and Cretaceous formations of the External Dinarides. A correlation is made among various parameters acquired from Rock-Eval, gas chromatography-mass spectrometry data and isotope analysis of carbonates and kerogen. Three groups of samples were analysed. The first group includes source rocks derived from Lower Jurassic limestone and Upper Jurassic “Lemes” beds, the second from Upper Cretaceous carbonates, while the third group comprises oil seeps genetically connected with Upper Cretaceous source rocks. The carbon and oxygen isotopic ratios of all the carbonates display marine isotopic composition. Rock-Eval data and maturity parameter values derived from biomarkers define the organic matter of the Upper Cretaceous carbonates as Type I-S and Type II-S kerogen at the low stage of maturity up to entering the oil-generating window. Lower and Upper Jurassic source rocks contain early mature Type III mixed with Type IV organic matter. All Jurassic and Cretaceous potential source rock extracts show similarity in triterpane and sterane distribution. The hopane and sterane distribution pattern of the studied oil seeps correspond to those from Cretaceous source rocks. The difference between Cretaceous oil seeps and potential source rock extracts was found in the intensity and distribution of n-alkanes, as well as in the abundance of asphaltenes which is connected to their biodegradation stage. In the Jurassic and Cretaceous potential source rock samples a mixture of aromatic hydrocarbons with their alkyl derivatives were indicated, whereas in the oil seep samples extracts only asphaltenes were observed.
  • Paleomagnetic investigations of the basal Borove Formation in the Liptov Depression (Central-Carpathian Paleogene basin)

    Abstract: The results of the paleomagnetic investigation from 9 localities of the Central-Carpathian Paleogene basal Borove Formation in the Liptov Depression (Central Slovakia) demonstrate complicated tectonic evolution in the central area of the Western Carpathians. The eastern rotations are predominant in the southern and western rotations in the northern margins of the Liptov Depression. Paleodeclinations vary from 92° to 269° and paleoinclinations from 7° to 59°. The dextral and sinistral fault systems explain different values of paleorotations in relatively closely situated localities. The obtained results generally support the model of tectonic escape from the south-west to north-east direction. Low inclination in some localities offers various explanations.
  • K-Ar geochronology and petrography of the Miocene Pohorje Mountains batholith (Slovenia)

    Abstract: A series of K-Ar ages from the Alpine Pohorje Mountains igneous complex is presented. The granodiorite with dacite was emplaced in a dynamic environment in the form of a single major intrusion, between 19–18 Ma (Ottnangian), into still hot metamorphic host rocks. The granodiorite includes an older mafic portion of transitional diorite to pyroxenite composition, cezlakite, yielding an age of ~20 Ma. Granodiorite magmatism was followed by major tectonic activity causing uplift of the Pohorje Mountains complex, and the whole batholith cooled rapidly at rather shallow depths, yielding uniform cooling ages of around 16.7 Ma, at the Karpatian/Badenian boundary. The process was accompanied by the intrusion of minor rhyodacitic dykes in the north-western part of the Pohorje Mountains complex and of thin lamprophyre dykes mostly into the metamorphic rocks on the western margin of the pluton. The pyroclastics within the Miocene sedimentary rocks attest to the latter’s young age and subaerial emplacement conditions. In the final stage of the magmatism, aplite-pegmatite melts intruded into the solidified granodiorite. The Pohorje Mountains batholith represents the westernmost intrusion along the extensional structures of the Pannonian Basin. The main magmatic activity could be related to deep transtensional fractures of the Labot fault system north of the Periadriatic zone. The tonalite and granodiorite from the Pohorje Mountains are petrologically different and younger than the Oligocene tonalite from Zelezna Kapla (Eisenkappel), as well as the tonalites further west, and the tonalites buried in the Zala Basin in Hungary (roughly between 40 to 30 Ma), which belong to Paleogene Periadriatic intrusions.
  • Application of grain-size trend analysis and spatio-temporal changes of sedimentation, as a tool for lagoon management. Case study: the Kotychi lagoon (western Greece)

    Abstract: The Kotychi lagoon is located on the northwest Peloponnese Greece, along a wave dominated and microtidal coast. The lagoon is one of the most important ecological areas in Greece, with international significance as it is protected by the Ramsar International Convention and is listing in the Natura (E.C.) Catalogue. For the present study 59 surficial samples were collected from the bottom of the lagoon, on a grid basis (approximately 300 m spacing) using a grab and were analysed for their grain size distribution as well as grain size parameters, mean, variance and skewness. Using the moment measures, grain-size trend analysis was made and the definition of trend vectors were estimated. Grain-size trend analysis indicates that the sediments of the lagoon are mainly sandy mud. Application of trend analysis indicates that the sediment pathways along the lagoon can be related to a) the sediments source area of the lagoon (small river supplies), b) wind related water circulation and c) the NW and SW wind directions. Moreover, comparing 1990 and 2000 satellite images we have detected three major areas where the shallow waters show a significant increase: area (a) in the northeast part of the lagoon, area (b) in the middle-west part and area (c) in the southern part. All these changes are related to river discharges and to the winnowing effect. Detection of changes in the coastline of the lagoon, showed a total reduction of areas covered by water by up to 13.8 %. The biggest change was detected in the northeast and in the southeast area of the lagoon and is related to the sediment supply from the periphery of the lagoon and to a minor degree to the bottom sediment pathway and winnowing effect. The rate of change of the area covered by water shows a rapid filling up of the lagoon and that additional measures have to applied for the protection of the lagoon ecosystem.
    A complete larva of a Mesozoic (Early Cenomanian) cockroach (Insecta: Blattaria: Blattulidae) from the Sisteron amber (Alpes de Haute Provence, SE France)

    Abstract: : A complete second-instar male larva of Nula sis gen. et sp.n., belonging to the cockroach family Blattulidae Vishniakova, 1982 is described from the Early Cenomanian amber of Sisteron in France. It reveals detailed and complete 3D morphology, with important presence of the central, 3rd ocellus, reduced in most adults and in all living cockroaches and termites, but present in some mantises. The modern distribution of unspecialized sensorial system of sensilla chaetica is also notable.