Tektonski položaj novih nalaza gipsa na Medvednici (sjeverozapadna Hrvatska)

In this paper two newly discovered locations with gypsum on Mt. Medvednica and the structural-tectonic setting are described. The first location with gypsum is situated 2 km S of Marija Bistrica and is associated with dolomites and clastic rocks of Permo-Triassic age, which were during the most recent Neotectonic events, together with Miocene sediments, intensely folded and reverse faulted under the influence of the main stress, oriented N-W. At the other location, in the upper course of the Vidovec stream, gypsum is also found in dolomite, which is in direct discordant contact with black Palaeozoic metapelites. On samples from both locations, sulphur isotope analysis was performed and an Upper Perm to Lower Triassic age was determined. Based on the results of the sulphur analysis it is assumed that investigated localities were connected with an open marine area during the Upper Permian. Therefore, and indirect conclusion concerning the age of the metamorphic rocks of Mt. Medvednica can be made. That is, gypsum occurs in both locations in non-metamorphic dolomites of the Upper Permian age.U radu su opisane dvije nove lokacije s gipsom na planini Medvednici kao i strukturno-tektonski položaj gipsa. Prva lokacija s gipsom nalazi se 2 km južno od Marije Bistrice i vezana je za dolomite i klastite permotrijaske starosti koji su tijekom najmlađih tektonskih događaja, zajedno s miocenskim sedimentima, intenzivno borani i reverzno rasjedani pod utjecajem djelovanja osnovnog stresa na pravcu sjever-jug. Na drugoj lokaciji, u gornjem toku potoka Vidovec, gips se nalazi također u dolomitu koji je u direktnom diskordantnom kontaktu s crnim metapelitima paleozojske starosti. Na gipsu s obje lokacije učinjena je izotopna analiza sastava sumpora i dobivene su starosti evaporita u rasponu gornji perm - gonji trijas. Na temelju rezultata analize sumpora zaključuje se na povezanost istraživanih lokaliteta sa širim marinskim prostorom za vrijeme gornjeg perma. S tim u svezi može se posredno zaključiti i o starosti metamorfnih stijena Medvednice. Naime, gips se na obje lokacije javlja u nemetamorfoziranim dolomitima gornjopermske starosti

Distribution of Iron and Manganese in Terra Rossa from Istria and its Genetic Implications

Haematite and goethite are the predominant pedogenic mineral phases in terra rossa from Istria. Limited variation of selected Fe oxide characteristics in analysed samples indicates the specific pedogenic environment in which terra rossa is formed. The mean value of the Fed/Fet ratio, taken as an index of weathering is 0.7 and reflects quite a high degree of weathering of Fe-containing primary silicates. Relatively uniform Fed/clay ratios clearly indicate a predominance of co-illuviation of clay and Fe oxides. Low values of Feo point to the low content of poorly crystalline Fe oxides in analysed terra rossa. Feo/Fed ratios in the analysed profiles vary. In the upper part of the Pomer, Porec and Novigrad profiles Feo/Fed ratios are higher than in the lower part of those profiles which may be explained as a result of different pedogenic environments and/or additions of external materials in the upper part of those profiles. The lack of positive correlation between Mnd and clay and Mnd and Fed is a consequence of remobilization of manganese due to hydromorphic processes which post-dated co-illuviation of clay and Fe oxides. During the Late Tertiary and Quaternary the pedogenic environment on hard carbonate rocks of the Jurassic-Cretaceous-Palaeogene carbonate plain of southern and western Istria generally remained suitable for rubification. However, (Neo)tectonic activity and the input of external material, as well as various climatic fluctuations might have significantly effected terra rossa through the processes of erosion, colluviation, yellowing and secondary hydromorphy

Distribution of Iron and Manganese in Terra Rossa from Istria and its Genetic Implications

Haematite and goethite are the predominant pedogenic mineral phases in terra rossa from Istria. Limited variation of selected Fe oxide characteristics in analysed samples indicates the specific pedogenic environment in which terra rossa is formed. The mean value of the Fed/Fet ratio, taken as an index of weathering is 0.7 and reflects quite a high degree of weathering of Fe-containing primary silicates. Relatively uniform Fed/clay ratios clearly indicate a predominance of co-illuviation of clay and Fe oxides. Low values of Feo point to the low content of poorly crystalline Fe oxides in analysed terra rossa. Feo/Fed ratios in the analysed profiles vary. In the upper part of the Pomer, Porec and Novigrad profiles Feo/Fed ratios are higher than in the lower part of those profiles which may be explained as a result of different pedogenic environments and/or additions of external materials in the upper part of those profiles. The lack of positive correlation between Mnd and clay and Mnd and Fed is a consequence of remobilization of manganese due to hydromorphic processes which post-dated co-illuviation of clay and Fe oxides. During the Late Tertiary and Quaternary the pedogenic environment on hard carbonate rocks of the Jurassic-Cretaceous-Palaeogene carbonate plain of southern and western Istria generally remained suitable for rubification. However, (Neo)tectonic activity and the input of external material, as well as various climatic fluctuations might have significantly effected terra rossa through the processes of erosion, colluviation, yellowing and secondary hydromorphy

Verification of Engineering-Geological/Geotechnical Correlation Column and Reference Level of Correlation (RNK) Method by Observations in the Slip-Plane Zone

The engineering-geological/geotechnical correlation column can be established in zones of limited extent using one or several characteristic layers, one of which is selected as the reference layer. The Reference Level of Correlation method, i.e. the RNK (Referentni nivo korelacije in Croatian) method, is a confirmed procedure enabling the establishment of such columns. In the engineering geological/geotechnical correlation column, the plasticity index is the most significant indicator of the peak friction angle, full-softening friction angle and residual friction angle for coherent soils and soft rock formations. As a rule, maximum plasticity index values correspond to the minimum values of such friction angles. This opens up the possibility of an exact engineering-geological/geotechnical model, with accurate differentiation of minimum shear strength zones, zones of different permeability, and zones of various degrees of natural compaction. This procedure was applied inter alia on the successfully improved Granice landslide located in the Zagreb area, where it was proven that elements for verification based on the RNK-method exist for all three areas of investigation: sliding body – drain trench section – detail in the central portion of the sliding zone. The procedure is recommended as a means for finding solutions to similar problems

A Middle Jurassic Radiolarite-Clastic Succession from the Medvednica Mt. (NW Croatia

On the NW part of Medvednica Mt. radiolarites with carbonate olistoliths, shales and siltites, matrix-supported conglomerates and basic volcanic rocks were investigated. This facies association is informally named the Poljanica unit. Major element geochemical data indicate deposition of radiolarites in the vicinity of the middle oceanic ridge, while sedimentological data indicate deposition in an area closer to the continent. Shales and siltites, as well as matrix-supported conglomerates, were deposited in short periods characterised by increased input of terrigenous material. Matrix-supported polymict conglomerates are composed of silicified shales, lithic graywackes, cherts and metabasalts, and were deposited by debris flow mechanisms as a consequence of synsedimentary tectonic activity. Carbonate olistoliths are composed of biomicrosparite, and jointly with deformed radiolarian cherts compose an olistostrome. Basic volcanic rocks represent high-Ti tholeiitic basalts formed in the MORB realm. Micropalaeontological investigation of radiolarite samples proved the Middle Jurassic (latest Bajocian - early Bathonian to late Bathonian - early Callovian) age of the Poljanica unit. Additionally, a new radiolarian species Theocapsomma medvednicensis n.sp. has been described. Conodont analyses from carbonate olistoliths in radiolarites proved their Triassic age. The investigated radiolarite-clastic succession is the result of subduction processes. Further continuation of this process caused incorporation of these deposits into the accretionary prism, where they were brought in direct contact with Triassic volcanic rocks and radiolarites (in the form of a tectonic mélange). Based on the lithological similarities with the Middle Jurassic turbidite-olistostrome successions in the Western Carpathians and Northern Calcareous Alps, the study area is considered to be part of the Meliata-Hallstatt Ocean

Strontium Dependence of the Lattice Constants of Barites from the Kresevo Area in Central Bosnia (Bosnia and Herzegovina)

The lattice constants of a synthetic BaSO4 and fourteen natural barite samples from the Kresevo area (Central Bosnia) were determined by X-ray powder diffraction. The natural samples contained from 0.3-17.6 mole % SrSO4, and negligible concentrations of Ca and Pb (<0.03 and 0.02 wt. %, respectively), thus representing almost pure (Ba,Sr)SO4 solid solutions. The diffraction lines of most natural samples were broadened in relation to those of synthetic BaSO4. This results from obvious compositional heterogeneity, e.g. the heterogeneous distribution of strontium, as is clearly observed from Sr variation patterns across a surface of the barite obtained by proton microprobe analysis. Nevertheless, the present values of unit-cell parameters are in agreement with those of synthetic (Ba,Sr)SO4 solid solutions documented in the literature. It has been proven that the interplanar spacing d004 may be used for determination of the Sr content of natural barites; the absolute error varies from ±0.3 mole % SrSO4 (for homogeneous samples having the diffraction line 004 clearly resolved in spectral doublet components) up to ±0.5 mole % SrSO4 (for the samples with compositional heterogeneity having a broadened and relative poorly defined diffraction line 004)

Triassic Pelagic Limestones in Pillow Lavas in the Oresje Quarry near Gornja Bistra, Medvednica Mt. (Northwest Croatia)

Investigated outcrops in the Oresje quarry near Gornja Bistra on Medvednica Mt. contain pillow lavas and massive metabasalts with fragments of carbonate rocks between them. The effusive rocks were determined as high-Ti tholeiitic metabasalts, corresponding to those which originated in the MOR area, which today represent obducted, allochthonous parts of Triassic oceanic crust. Carbonate rock fragments are characterised by micrite, biomicrosparite, fossiliferous microsparite, biosparite and sparite types, all of which are more or less recrystallised. From their appearance between pillows, together with hyaloclasts they were determined as peperites. Micropalaeontological analysis of conodonts from the limestone samples indicated a Middle Triassic age, which is also the age of the effusive rocks discovered in the quarry

Glauconitic Materials from Lower Miocene Macelj-Sandstones of the Hrvatsko Zagorje, North-Western Croatia

The Lower Miocene Macelj-sandstones, from the western part of Hrvatsko Zagorje, are green in colour with variable amounts of glauconitic grains. This paper presents the results of mineralogical and some petrological analysis of three characteristic samples of these sandstones. The natural sandstone samples were analysed by polarising microscope and by X-ray powder diffraction (XRD). After separation, the pure or almost pure glauconitic materials were analysed by XRD, chemical analysis and thermal analysis (TG, DTA and DTG). The results show variation, not only in the glauconitic material of the sandstone samples, but also within individual samples. The amount of smectite layers varies from <5% to approximately 40% depending on the degree of order and the stage of glauconite evolution. This is indicated by the contents of K, Al, Fe, adsorbed water and cation exchange capacity as well as XRD powder patterns

Strontium Dependence of the Lattice Constants of Barites from the Kresevo Area in Central Bosnia (Bosnia and Herzegovina)

The lattice constants of a synthetic BaSO4 and fourteen natural barite samples from the Kresevo area (Central Bosnia) were determined by X-ray powder diffraction. The natural samples contained from 0.3-17.6 mole % SrSO4, and negligible concentrations of Ca and Pb (<0.03 and 0.02 wt. %, respectively), thus representing almost pure (Ba,Sr)SO4 solid solutions. The diffraction lines of most natural samples were broadened in relation to those of synthetic BaSO4. This results from obvious compositional heterogeneity, e.g. the heterogeneous distribution of strontium, as is clearly observed from Sr variation patterns across a surface of the barite obtained by proton microprobe analysis. Nevertheless, the present values of unit-cell parameters are in agreement with those of synthetic (Ba,Sr)SO4 solid solutions documented in the literature. It has been proven that the interplanar spacing d004 may be used for determination of the Sr content of natural barites; the absolute error varies from ±0.3 mole % SrSO4 (for homogeneous samples having the diffraction line 004 clearly resolved in spectral doublet components) up to ±0.5 mole % SrSO4 (for the samples with compositional heterogeneity having a broadened and relative poorly defined diffraction line 004)