GA AV

The project is focused on architecture of the Barrandian Prague Basin (Ordovician to Devonian between Prague and Plzeň), where the stratigraphy and palaeontology are well advanced but the data and reliable interpretations on tectonics are mostly absent. Previous data suggest variety of deformation styles, paleomagnetic directions, geochemical features, sedimentary facies and diagenetic alterations in individual units of the Basin. Pricipal goals of the project are to produce and interpret new data that will originate within a framework of cooperating working groups dealing with tectonics, paleomagnetism, geochemistry, facies and diagenesis. The project will cover the present voids in knowledge on nature and evolution of the Prague Basin fill, tectonic styles and deformational units. The project will contribute to the recent sum of informations on early evolution of Variscan terrane mosaic of the Bohemian Massif as a part of the Variscan central Europe.

Large graptolite material have been collected in the Hlinsko Zone by bulk sampling of the Silurian black slates and cherts of the Mrákotín Formation. This fauna and specimens deposited in museum collections will undergo systematic taxonomic description and will be further interpreted from both biostratigraphic and palaeogeographic/ palaeoenvironmental viewpoints. Present, still scattered biostratigraphic data on the lower Silurian of the Hlinsko Zone will be completed and original sedimentary succession of its badly tectonized and poorly exposed strata will be reconstructed, in particular by means of detailed biostratigraphic correlation with Barrandian area, Thuringia and Bardo Mountains. A lithostratigraphic correlation of biostratigraphically subdivided sedimentary succession of the Mrákotín Formation will help to elucidate palaeogeographic position of the Lower Palaeozoic of the Hlinsko Zone within the Variscan units of the Bohemian Massif.

The distribution of upper mantle and deep crustal (ultra)mafic xenoliths in Cenozoic volcanics of the Bohemian Massif (BM) will be studied with special reference to compositional and textural variations and metasomatic effects in the upper mantle. The model occurrences selected for each rock type/association of xenoliths during a pilot study will reflect different positions within the taphrogenic structures of the BM. Geochemical data will be used for modelling of PTX conditions of the crystallization of xenoliths and the host rocks. Their subsequent thermal history will be determined using the fission tracks method. From the data obtained, depths of their origin will be estimated, and different genetic models will be formulated to explain the genesis of xenolith associations in different areas of the BM and at different positions within taphrogenic structures. These results will be combined with geophysical data (e.g., BOHEMA project) to model the deep structure of the Ohře Rift.

Going open-cast mining at former Jan Šverma Mine provides very good and the last chance for palaeoecological research of Upper Carboniferous (lower Westphalian) swamp biotopes of the Intra Sudetic Basin. It is just the only mine with opencast black coal-mining in the Czech Republic. Coal-mining activities will continue only for a few next years. The project combines sedimentological, geological and palaeontological methods of research. The main aims of the project are: -characterisation of fossil plant assemblages, their specific and generic composition, palaeoecological characterisation of biotopes, -characterisation of sedimantary environment and main sedimantary processes of swamps of studied coal seams and clasic systems where coal seams originated. This type of research has never been done in the Intra Sudetic Basin.

Near-contact silicification along intrusive/volcanic bodies and large-volume silicification beneath sealing horizons are the two types of hydrothermal alteration with newly formed SiO2 in coarse clastics of the fill of the Ohře Rift graben (Oligocene to Miocene), its floor and its shoulder blocks (Late Cretaceous). Their association with other types of young minerelization like ferruginization, fluoritization and barization will be taken as a circumstance permitting to trace the development of mineralizing fluids (chemistry, temperature, pH) through time. The function of faults, fracture zones and intrusive/volcanic bodies as elements of convective fluid transport will be particularly established. The respective hydraulic model will be constructed for marginal zones of the Ohře Rift and compared with fluid circulation patterns on other rift basins in the world.

The palaeomagnetic and magnetostratigraphic research of fluvial and chemogenic cave sediments in selected karst areas in Slovenia, Slovakia, Hungary, Poland and Bohemia will be focussed on reconstruction of sedimentary processes both in caves and surface river systems. The stratigraphic correlation of sedimentary sequences from different karst areas will allow us to assess generaly operating mechanisms controlling character of surface and subsurface drainage. Changes in stream discharge, vegetation density, erosion intensity and weathering will be studied based on mineral magnetic indicators (anisotropy of magnetic susceptibility, phase changes, magnetic grain size, etc.) with the aim to define conditions, which influence these processes. Obtained results help to evaluate the conditions and history of speleogenesis in different karst areas in the Central Europe.

The goal of proposed study is to establish the petrogenetic evolution of the intraplate nephelinite to tephrite series (37-30 Ma), characteristic in high- and low-Ti contents and located in the riftogenic setting. The high-Ti rock types are characterized not only by distinctive high TiO2 contents (2.6-5.0 wt%), but also by Ti/Y ratios >500, similarly to basaltic (or tholeiitic) rocks in the LIPs. The low-Ti types exhibit <2.6 wt% TiO2 and Ti/Y ratio<500. Petrological and geochemical studies (electron microprobe, determination of trace elements using ICP-MS, INAA, PIGE and PIXE methods, Sr-Nd-Pb, oxygen stable isotopes, and K-Ar age determination) will be accomplished to constrain the comagmatic relations to one or several magmatic sources (degree of decompression melting, magmatic mixing/mingling and of lithospheric contamination). Rock magnetic properties and opaque mineralogy will contribute to interpretation of lava flows with both normal and reversal magnetic polarity.

Principal aim of the project is to study the larval development of the Oligocene genus Eopelobates (Anura: Pelobatidae), based on a series of premetamorphic and metamorphic tadpoles. The tadpoles are preserved as skeletons and soft tissue parts, and may be compared with data on the development of Eopelobates anthracinus and Pelobates decheni from the late Oligocene of Germany. These fossil samples will be compared with corresponding information on the development of contemporary Pelobates, which will make it possible to assess evolutionary trends of complete ontogenies, during the period Oligocene-Recent. The mentioned developmental series are the only ones which represent non-pipoid anurans. Also recently discovered tadpole from the late Jurassic of China seems to belong neither to Palaeobatrachidae nor to Pipidae. Information on the development of both fossil and recent Pelobatidae may supposedly help to clarify the problem of North American late Cretaceous "Eopelobates".

The August flood of 2002 represented the largest Czech flood of the last 500 years and thus exceptional opportunity to study episodic processes. The documentation of morphological features and profiles had begun immediately after the flooding. Project is aimed for (1) the recognition of principal erosional and accumulative high flood processes; (2) the monitoring of flood plain development including destruction, bioturbation and incorporation of flood sediments into soil cover; (3) petrological, mineralogical and geochemical characteristics of flood sediments including leaching and mobility study of selected trace elements; (4) study of unusual phenomena related to water oversaturated sediments such as urban subsurface erosion, solifluction, trost cracking and trost diapirism. Besides an usual scientific output a popular monograph written for people living in inundated areas and focused on impact of future possible floods will be prepared.

The project is aimed at the understanding of the elementary soil processes which contributed to the Pleistocene and Holocene development of structure soil cover in the protected areas of Prague. The wide spectrum of soil types will represent a basis for monitoring of environmental changes, soil regimes and specification of complex soil microprocesses. The environmental impacts can be characterized by a set of soil analyses primarily including soil micromorphology, mineralogy and clay mineralogy, geochemistry, geomorphology and malacozoology. The network of soil profiles will also permit a comparison of pedogenic processes with fossil soils whose individual developmental stages were affected by no human activity.