New Mississippian trilobite association from the Brno vicinity and its significance (Moravian Karst, Czech Republic)
Abstract: Eleven trilobite species (Archegonus (Archegonus) aequalis philliboloides R. Hahn, 1967, Bollandia persephone (Hahn & Hahn, 1970), Bollandia cf. megaira (Hahn & Hahn, 1970), Liobole (Panibole) cf. jugovensis (Osmólska, 1968), Liobole (Sulcubole) glabroides (Richter & Richter, 1949), Semiproetus (Macrobole) drewerensis latipalpebratus (Osmólska, 1973), Proliobole vigilax (Chlupac, 1961), Cyrtoproetus (Cyrtoproetus) cracoensis cracoensis (Reed, 1899), Carbonocoryphe (Carbonocoryphe) bindemanni Richter & Richter, 1950, Tawstockia (Beleckella) milleri (Hahn & Hahn, 1971), Cummingella (Cummingella) cf. auge Hahn & Hahn, 1968) are described for the first time from the shales of the Brezina Formation in Mokra Quarry near Brno (Bohemian Massif, Moravian Karst). This typical trilobite association — comparable to that previously described from the Erdbacher Kalken of Steeden in Hessen (Germany) — was found during excavation in the Mokra Quarry but they do not come from the exact Tournaisian-Visean boundary. Stratigraphical correlation and comparison of material is mentioned below, as is the history of the trilobite research from the Moravian Karst.
Permian volcanics in the Northern Gemericum and Borka Nappe system: U-Pb zircon dating and the implications for geodynamic evolution (Western Carpathians, Slovakia)
Abstract: U-Pb dating (SHRIMP) of magmatic zircon ages from the Northern Gemericum Permian volcanics (Petrova Hora Formation) yielded the Concordia age of 272.4±7.3 Ma for basaltic andesite, as well as the Concordia age of 275.2±4 Ma for rhyodacites. Both zircon ages correspond to the Cisuralian Epoch in the time span of the Kungurian Stage. Acquired 206Pb/238U zircon age data support the nearly contemporaneous origin of the acid and basic volcanogenic members in the Northern Gemericum Permian strata. The bimodal volcanic suite proves the transtension/extension tectonic regime in the North Gemeric sedimentary basin during the Late Cisuralian. The magmatic zircon ages of rhyodacites, occurring in the lower thrust sheet of the Borka Nappe (Jasov Formation), gave a younger Concordia age of 266±1.8 Ma proving the Guadalupian Epoch, in the time span of the Wordian/Capitanian. In comparison to the Northern Gemericum realm, this age refers to the relatively younger stage of rift-related extensional movements. In the wide Alpine-Dinarides realm the Middle Permian (Guadalupian) movements are related to the beginning of the Alpine sedimentary cycle. Thus, the Middle Permian rifting expresses the beginning of the formation of the future Meliata oceanic trough.
Nannofossil record across the Cenomanian–Coniacian interval in the Bohemian Cretaceous Basin and Tethyan foreland basins (Outer Western Carpathians), Czech Republic
Abstract: Nannofossil biostratigraphy and mutual correlation was worked out for the Cenomanian-Coniacian deposits of the Bohemian Cretaceous Basin (BCB) and Outer Western Carpathians (OWC) in the territory of the Czech Republic. Similar assemblages of the BCB and from sediments deposited on the SE slopes of West European Platform, Waschberg-Zdanice-Subsilesian Unit, OWC support the hypothesis that the two areas were connected by a sea way (nowadays the Blansko trough). The nannoflora of the Silesian Unit, OWC show more afinity to high latitudes as is documented by the presence of Marthasterites furcatus in the Lower Turonian, UC6b and UC7 Zones. Turonian and Coniacian deep-water flysch sediments of the Silesian Unit and Magura Group of Nappes provide nannofossils on rare occassions. Strongly atched nannofossils dominated by W. barnesiae from Cenomanian black shales of the BCB are comparable to those of the Silesian Unit and reflect a similar shallow nearshore sea. In the BCB, uppermost Cenomanian is marked by the last occurrence (LO) of Axopodorhabdus albianus and first occurrence (FO) of Quadrum intermedium (6 and 7 elements) and lowermost Turonian by a sudden quantitative rise in nannoflora and by the FO Eprolithus octopetalus. First Eiffellithus eximius and thus the base of the UC8 Zone was recorded in the upper part of ammonite Zone Collignoniceras woollgari in the lower Middle Turonian. Lithastrinus grillii is the stratigraphically youngest nannofossil species in this region and indicates the uppermost Coniacian. In the OWC, the Albian-Cenomanian boundary was recorded in the Silesian Unit and is marked by the LO Crucicribrum anglicum and FO Prediscosphaera cretacea and Corollithion kennedyi in the uppermost Albian. The Turonian-Coniacian boundary found both in the BCB and Waschberg-Zdanice-Subsilesian Unit, OWC is indicated by the FO Broinsonia parca expansa and by the base of the interval with common Marthasterites furcatus. In both areas, events were found closely below the FO inoceramid species Cremnoceramus waltersdorfensis. The Coniacian-Santonian boundary interval (Waschberg-Zdanice-Subsilesian and Foremagura Units, OWC) is indicated by Lithastrinus grillii occasionally accompanied by Lucianorhabdus ex gr. cayeuxii, Hexalithus sp. and Arkhangelskiella specillata.
Correlation of bio- and magnetostratigraphy of Badenian sequences from western and northern Hungary
Abstract: Lithological, magnetostratigraphic and paleontological (nannoplankton, foraminifers, molluscs) studies were carried out on the Badenian successions of boreholes Sopron-89, Nagylózs-1 and Sata-75 in Hungary. The correlations with the ATNTS2004 scale show that the Badenian sedimentation began during Chron C5Br thus the earliest Badenian deposits are missing in the sections. The first occurrence of Orbulina suturalis Brönnimann has been observed in Subchron C5Bn.1r, at 14.9 Ma. Although it is older than the interpolated age of 14.74 Ma in Chron C5ADr in the ATNTS2004, it is consistent with the age of 15.1 Ma obtained from recent calibration of planktonic foraminiferal bioevents. The base of the Bulimina-Bolivina Zone has been determined at 13.7 Ma in Chron C5ABr, and the Badenian/Sarmatian boundary is recorded within Chron C5AAn, at 13.15 Ma.
The resistivity image of the Muran fault zone (Central Western Carpathians) obtained by electrical resistivity tomography
Abstract: The paper describes the application of geophysical prospecting techniques for estimation of the fault’s inclination. The field survey was carried out across the Muran fault structure in the Slovenske rudohorie Mts (central Slovakia). Three different geophysical methods were used to map the fault zone: Electrical Resistivity Tomography (ERT), induced polarization (IP) and radon emanometry. All these methods have been used to locate the fault zone area, but the principal aims of this research are to test the efficiency of the 2D ERT technique to recognize the geometrical characterization of the fault and to improve our tectonic knowledge of the investigated area. For the synthetic cases, three geometric contexts were modelled at 60, 90 and 120 degrees and computed with the l2 norm inversion method, the l1 norm with standard horizontal and vertical roughness filter and the l1 norm with diagonal roughness filter. In the second phase this geophysical methodology was applied to fieldwork data. Our results confirm that the ERT technique is a valuable tool to image the fault zone and to characterize the general geometry, but also the importance of setting up the right inversion parameters. The main contribution of the geophysical investigations in this case was the determination of the location and confirmation of the inclination of the Muran fault. The result of this study is the ability to make a visual estimation of the direction and dip of the fault. Pursuant to this work the dipole–dipole electrode configuration produces the best resolution, particularly for the location of vertical and dipping structures. The advantage of this array is that it shows the ability to assess the trend of the dip and therefore it can be strongly recommended. The result is also a case study of a small scale tectonic survey involving geophysical methods.
Geochemistry and electron spin resonance of hydrothermal dickite (Nowa Ruda, Lower Silesia, Poland): vanadium and chromium
Abstract: Geochemical analyses for trace V and Cr have been done on a representative sample of a typical hydrothermal dickite/kaolinite filling vein at Nowa Ruda. The mineralogy of the sample is comparatively simple, dickite being the principal component (ca. 91 % of the total sample). Geochemical fractionation and inductively coupled plasma-optical emission spectrometry (ICP-OES) indicate that most (>90 % of total metal) of the V and Cr reside in the dickite. Electron Spin Resonance (ESR) shows that most (>70 %) of the V in the dickite structure is in the form of vanadyl (VO2+) ions. A high concentration of Cr3+ is also detected in this structure by ESR. The combination of geochemical and spectroscopic tools applied to VO2+ and Cr3+ allow one to specify the Eh (>0.4 V, highly oxidizing) and pH (L4.0, highly acidic) of the solution during the formation of dickite from the Nowa Ruda Basin. Substantial proportions of the V and Cr (as well as VO2+ and Cr3+) in the dickite structure were probably contained in an original hydrothermal acid water. We suggest that hot hydrothermal waters leached the surrounding varieties of gabbroids enriched in V and Cr for the dickite-forming solution. The results of this work have shown V and Cr are potentially reliable indicators for geochemical characterization of the physicochemical conditions of their formation. The bulk-rock V/Cr ratio in hydrothermal dickites and kaolinites from Nowa Ruda, Sonoma (California, USA), Cigar Lake (Saskatchewan, Canada) and Teslic (Bosnia and Hercegovina) is also briefly explored here as a potential tracer of redox state during their formation.