GA AV

The youngest and more than 1,000 m thick sequence of the Central and Western Bohemian Basins is represented by the Líně Formation. There are up to 10 often fossiliferous lacustrine horizons and the Horizon of Conglomerates with carbonate pebbles. Comparison of interpreted facies with ichnologic and paleontologic data enable to assign the corresponding paleoenvironments and paleoclimates near the Carboniferous/Permian boundary. The paleocurrent, facies, and fossil communities analyses can clarify paleogeographic situation of the tropical zone of Pangea. Provenance of the unique marine carbonate Paleozoic pebbles will be solved with help of micropaleontology. Large scale tectonic elements will be studied with help of GIS analysis of remote sensing data and digital elevation model. The Ichnofabric Index will be determined in continuous profiles and drill cores. The vertebrate assemblages (obtained also by chemical way) integrated with correlation of well logs can solve stratigraphy.

The main aim of the project is to study flowers, inflorescences and pollen in situ at fossil plants of the Peruc-Korycany Formation within the Bohemian Cretaceous Basin. Methodology which have not yet been applied, will be used. The project is focused on detailed study of flowers and their pollen ncluding study of exina sculptation (using high resolution SEM) and pollen ultrastructures (using TEM). The project follows up with results of previously finished projects on infructescences, fruits and seeds. Another aim of the project is to compare pollen grains known from dispersed pollen spectra with pollen found in situ. This will help to determine systematical affinity of pollen grains classified till now only by names of formal palynomorph nomenclature. New data on Cretaceous plants and their pollen in situ will be used for palaeoecological interpretations and reconstructions for purposes of exhibition of the National Museum and lectures on palaeontology in the Charles University.

Mantle pyroxenites represent the second most common mantle rock found in maficultramafic series. They usually form layers or veins of variable size and shapes and their composition ranges from orthopyroxenites through websterites to clinopyroxenites, usually with variable amounts of olivine. In spite of their common abundance (especially in large orogenic peridotite bodies), their origin is still matter of debate. Early work of Dick and Sinton (1979) and also Chen et al. (2001) suggested in-situ melting/dissolution of pyroxenes and their consequent precipitation in pyroxenite layers. In contrast, prevalent studies explained pyroxenites as rocks formed by crystal precipitation from silicate melts passing through the lithospheric mantle (e.g., Frey, 1980; Loubet and Allegre et al., 1982). Finally, Davies et al. (1993), Pearson et al. (1993) or Medaris et al. (1995) suggested that mantle pyroxenites represent high-pressure cumulates from subduction-related melts and therefore, they can provide insights to crustal recycling into the upper mantle. Highly siderophile element (HSE - Os, Ir, Ru, Rh, Pd, Pt, Re, Au) studies provide unique and complex view on mantle refertilization. This is because these elements behave in a different way during partial melting and they are concentrated in different phases (e.g., sulphides, alloys) to different degrees. All these features lead to HSE fractionation during upper mantle processes such as magma generation/differentiation or metasomatism. The Re- Os isotopic system provides another unique tool for understanding mantle refertilization due to the Re fractionation from Os during melt generation. This is because Re behave incompatibly during melting whereas Os is strongly compatible and retain in the source (Carlson, 2005 and references therein). As a consequence, melting products of upper mantle (basalts) are characterized by much higher Re/Os ratios and more radiogenic 187Os/188Os then upper mantle.
Pyroxenites plays very significant role in processes of mantle refertilization and enrichment. Therefore, their study provide direct insights into these processes, which are, in turn, very important for genesis of numerous mantle-derived melts. This project is focused on distribution and fractionation of highly siderophile elements and Re-Os geochemistry of upper mantle pyroxenites representing different mantle sources (oceanic vs. subcontinental) and on study of peridotite-pyroxenite interaction (mixing).