Jiří Kalvoda

A high-resolution, multiproxy stratigraphic analysis of the Devonian–Carboniferous boundary sections in the Moravian Karst (Czech Republic) and a correlation with the Carnic Alps (Austria)

A multidisciplinary correlation of the Devonian–Carboniferous (D–C) boundary sections from the Moravian Karst (Czech Republic) and the Carnic Alps (Austria), based on conodont and foraminifer biostratigraphy, microfacies analysis, field gamma-ray spectroscopy (GRS), carbon isotopes and element geochemistry, is presented in this paper. The study is focused on the interval from the Middle Palmatolepis gracilis expansa Zone (Late Famennian) to the Siphonodella sandbergi Zone (Early Tournaisian). In Lesni lom (Moravian Karst), a positive δ 13 C excursion in the Bisphatodus costatus – Protognathodus kockeli Interregnum from a distinct laminated carbonate horizon is correlated with a carbon isotope excursion from the Grune Schneid section of the Carnic Alps and is interpreted as the equivalent of the Hangenberg black shales and a local expression of the global Hangenberg Event sensu stricto . Higher up at both sections, a significant increase in the terrigenous input, which is inferred from the GRS signal and elevated concentrations of terrigenous elements (Si, Ti, Zr, Rb, Al, etc.), provides another correlation tieline and is interpreted as the equivalent of the Hangenberg sandstone. Both horizons are discussed in terms of relative sea-level fluctuations and palaeoceanographic changes. Recent studies show that conodont biostratigraphy is facing serious problems associated with the taxonomy of the first siphonodellids, their dependence on facies and discontinuous occurrences of protognathodids at the D–C boundary. Therefore, the correlative potential of geochemical and petrophysical signatures is high and offers an alternative for the refining of the problematic biostratigraphic division of the D–C boundary.

Polyphase deformation of the Variscan accretionary wedge: an example from the southern part of the Moravian Karst (Bohemian Massif, Czech Republic)

Abstract The presence of two different coeval pre-flysch carbonate facies juxtaposed in numerous profiles in the southern part of the Moravian Karst proves that the Variscan nappe tectonics affected the pre-flysch basement of the main Culmian flysch nappes. Two main thrust events were recognized: (1) a ‘thin-skinned’ event, during which two sedimentary facies were juxtaposed along bedding sub-parallel thrusts, and (2) a ‘thick-skinned’ event, which generated younger thrusts oblique to bedding, involved crystalline rocks of the Brno Massif, and resulted in refolding of the older thrusts.

New Mississippian trilobite association from the Brno vicinity and its significance (Moravian Karst, Czech Republic)

New Mississippian trilobite association from the Brno vicinity and its significance (Moravian Karst, Czech Republic) 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 (Chlupáč, 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 Březina Formation in Mokrá 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 Mokrá 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.

Late Chadian–early Arundian high-resolution biostratigraphy in the Ogmore-by-Sea section (South Wales–Mendip shelf) and the mid-Avonian unconformity

The study of the foraminiferal fauna in the Ogmore section in south Wales produced a detailed late Chadian–early Arundian biostratigraphy and sequence stratigraphy with a higher resolution than in the Arundian stratotype in Hobbyhorse Bay. The earliest Visean (late Chadian) pedogenic horizon close to the Gully Oolite and Caswell Bay Mudstone boundary (MFZ9) corresponds to the mid-Avonian unconformity. The entry of primitive archaediscids of MFZ10 within the Caswell Bay Mudstone is followed by more advanced archaediscids of MFZ11 at the base of the High Tor Limestone. The mid-Avonian unconformity at the Chadian–Arundian boundary is not confined to the London–Brabant Massif, but is also present in central Europe, the East European Platform, the Urals, west Siberia and probably also in Kuzbass and North America. The global extent of the the mid-Avonian unconformity suggests that it is a consequence of early to mid-Visean glacioeustacy.

Biostratigraphic and sedimentary record of the Annulata Events in the Moravian Karst (Famennian, Czech Republic)

The biostratigraphy and facies of halfgraben limestones in the southern part of the Moravian Karst (Czech Republic) have been studied from Uppermost Palmatolepiscrepida to Upper Palmatolepisgracilisexpansa conodont Zones. Only one Annulata Event horizon was detected, reflecting condensed sedimentation with the possible influence of erosion on the bypass slope. The “Wagnerbank” equivalent above the Annulata Events in the uppermost part of the Upper Palmatolepis rugosa trachytera Zone was not clearly recognized. The conodont data suggest the event beds in the Ochoz, Hostěnice 2, and Mokrá sections represent the Lower Annulata Event. Correlation of the Annulata Event bed in the Hostěnice 1 section with the Upper Event remains tentative. Recorded microfacies were deposited slightly below or above the storm wave base. The Annulata Event beds correspond to mudstones/wackestones to floatstones/rudstones with cephalopods and other fauna. Other microfacies include mostly various wackestones to packstones up to floatstones/rudstones. Conodont biofacies show the increase in both epipelagic taxa in the Annulata Event beds and “granulated” polygnathids above the Annulata Event beds. The cause of the increase in alternognathids in the Annulata Event beds remains questionable. Both the microfacies and conodont biofacies are generally similar to those seen widely distributed in other European and Moroccan sections, thus documenting the global nature of the Events.

PRELIMINARY REPORT ON THE NEW FINDINGS OF MISSISSIPPIAN TRILOBITES IN THE BŘEZINA FORMATION (MORAVIAN KARST, CZECH REPUBLIC)

New fossiliferous layers of the Březina Formation were discovered in the valley of the Řicka Brook SSW of the village of Ochoz u Brna in 2011. Four taxa of trilobites were preliminary determined: Archegonus (Phillibole) cf. polleni (Woodward, 1894), Archegonus (Phillibole) cf. cauliquercus Brauckmann 1981, Liobole (Liobole) glabra proxima Chlupac, 1966 and ?Spinibole sp. The newly discovered fossiliferous beds belong to the Visean (Lower to ?Upper Visean, approximately cu IIγ–cu IIδ). The occurrence of limestone pebbles and limestone cobbles in aleuropelitic shales was also recorded. The Late Tournaisian foraminifer Darjella monilis Malakhova, 1964 was discovered in a dark grey limestone cobble derived from the Hady-Řicka limestone sequence of the Liseň Formation.

Microproblematica, calcareous algae, and microbialites at the Frasnian-Famennian boundary interval in the Šumbera section (Moravian Karst, Czech Republic) and their significance in the context of the Kellwasser Crisis

The Kellwasser Crisis represents one of the most severe extinction events in the Phanerozoic. The Šumbera section (Moravo-Silesian Basin, Moravian Karst) spans the Upper rhenana to Palmatolepis minuta minuta (or younger) conodont zones and corresponds to the upper part of a carbonate ramp with material derived from shallower areas. A rich association of calcareous algae, cyanobacteria, and microproblematica, comprising renalcids (Izhella), Girvanella, Rectangulina cf. tortuosa, Rothpletzella, “solenoporaceans”, “Keega”-like microfossils, udoteacean alga Paralitanaia, volvocean and radiospherid calcispheres, palaeoberesellids, Umbellina bella, and Wetheredella, is similar in diversity to associations known from China, Australia, Canada, and Belgium. The Šumbera section represents a unique locality where changes in shallow-water biota at the Frasnian-Famennian boundary are well calibrated by detailed conodont biostratigraphy. We track in detail the evolution of shallow-water biota and the features that are often discussed in the context of “anachronistic” facies, such as flourishing microbial structures, enhanced early marine cementation, and flat-pebble conglomerates. Some features which could be indicative of environmental stress such as flat-pebble conglomerates developed during the Frasnian part of the Kellwasser Crisis (Upper rhenana to linguiformis Zones), whereas a renalcid boom started at the Frasnian-Famennian boundary.

Annulata event z profilu v jámovém lůmku u Ochozi u Brna -poznámky ke konodontové biostratigrafii (famen, Moravský kras)

About two meters thick section of the Famennian Křtiny Limestones (Liseň Formation) was studied in a small pit-quarry near the road leading from Brno-Liseň to Ochoz u Brna. Conodont samples were taken from seven diff erent stratigraphical levels. A richly fossiliferous interval (about 40 cm thick) can be distinguished in the higher part of the section. This interval is characterized by abundant occurence of clymenids, bivalves, orthocone nautiloids, trilobites and other groups. Black limestone lenses (maximal thickness about 10 cm) are developed in the lowermost part of the richly fossiliferous interval. A presence of Palmatolepis glabra lepta (late morphotype), Palmatolepis minuta minuta and Palmatolepis rugosa trachytera suggests these black limestones probably represent the Lower Annulata event (Upper Palmatolepis rugosa trachytera zone). Polygnathus styriacus indicating the base of the Palmatolepis perlobata postera zone enters within about 10 centimeters thick interval of dark grey biodetritic limestones which occur closely above the black limestone lenses. The Upper Annulata event and equivalents of „Wagnerbank“ or „Annulata limestone“ were not distinguished in the studied section. This might be caused by condensed sedimentation. Grey limestones and marly limestones belonging to the higher part of the richly fossiliferous interval are placed above the base of the Palmatolepis perlobata postera zone. The studied locality might correspond to the original fossil site described by Rzehak in 1910.

PETROFYZIKÁLNÍ CHARAKTERISTIKA HRANIČNÍHO INTERVALU DEVONU A KARBONU V MORAVSKÉM KRASU

The first results of the petrophysical research (gamma-ray spectrometry, magnetic susceptibility, diffuse spectral reflectance) of the Devonian/Carboniferous boundary interval in the southern and middle part of the Moravian Karst demonstrate a good correlation potential of outcrop logging by gamma-ray spectrometry. This method allows us to correlate distinct petrophysical patterns through the different lithofacies developments (Horakov and Hostěnice facies), while magnetic susceptibility and diffuse spectral reflectance failed to show correlatable patterns. The most prominent petrophysical patterns at the sections can be correlated with the polyphase Hangenberg Event.