Richard Pokorný

Ultra-trace analysis of Hg in alkaline lavas and regolith from James Ross Island

Abstract Polar regions represent a unique environment for the study of mercury cycling in the global ecosystem. Our research was focused on the assessment of the origin and mobility of mercury in the geochemical cycle in Maritime Antarctic (James Ross Island) by means of atomic absorption spectrometry. Mercury content in a set of extrusive (subaerial, subaqueous) and intrusive (dyke) alkaline basalts ranged between 1.6 µg kg-1 (for samples without xenoliths) and 8 µg kg-1 (for samples containing crustal xenoliths). The mercury content in alkaline basalts indicates a very low concentration of mercury in peridotitic mantle sources. Samples of regolith from James Ross Island were subjected to a comprehensive analytical procedure proposed for ultra-trace mercury concentrations involving fractionation and thermal analysis. Total mercury contents in regolith (2.7–11.3 µg kg-1) did not deviate from the natural background in this part of Antarctica. Additionally, the obtained results are about two orders of magnitude smaller than values formerly assumed for primary mercury contents in basaltic lavas. Our results from Antarctica were compared with mercury contents in basaltic rocks from Greenland and the findings were confirmed. It seems that the input of mercury of geological origin into the polar ecosystem is apparently lower than expected.

Funalichnus, a New Ichnogenus and its Type Ichnospecies Funalichnus strangulatus (Fritsch 1883), Upper Cretaceous of the Bohemian Cretaceous Basin, Czech Republic

Trace fossils with an appearance corresponding to the description of Fucoides strangulatus Fritsch 1883 were found at two localities of the Bohemian Cretaceous Basin. The genus Fucoides does not correspond to the modern concept of paleontologic (and particularly paleoichnologic) taxonomy. Therefore, the specimens are assigned to a new ichnogenus, Funalichnus, and its type ichnospecies Funalichnus strangulatus (Fritsch 1883). Some specimens previously identified as the ammonite of the genus Hamites probably also represent the ichnospecies Funalichnus strangulatus.

Basaltic Dyke with Specific Volcanogenic Structures and Its Geomorphic Evolution: Unique Geoheritage of the Faroe Islands (North Atlantic Ocean)

Volcanic landforms resulting from Cenozoic volcanism represent the most peculiar features of global geodiversity and provide eminent narratives for geoeducation. Among them, however, relict volcanic forms and site-specific landforms in remote areas have received less attention. In this paper, we provide the first description of unique volcanogenic features (hereinafter referred to as pseudo-hieroglyphs) developed on a summit rock wall at the Sandfelli ridge near the village of Gjógv in the N Eysturoy Island (Faroe Islands). The geomorphic evolution of the ridge and rock wall during the Quaternary is described and detailed petrographic analyses of the volcanogenic features are provided. Based on observed petrographical features, we interpret the pseudo-hieroglyphs to probably represent unique examples of chaotic horizontal columnar jointing. Following the geomorphological and petrographic examination of the study site, we analyse current Faroese legislation aiming at nature conservation and use this case to discuss broader implications of geoheritage conservation and geotourism in distant regions.

Late Holocene soil processes and the first evidence for ferruginous rhizoconcretions in cool subpolar environments of the Faroe Islands

ABSTRACT The Faroe Islands are characterized by high rates of Holocene geomorphological activity and demonstrable vegetation change, including substantial peat formation. Pedogenesis, especially in the late Holocene, is less well known. Numerous ferruginous rhizoconcretions consisting predominantly of Fe-oxyhydroxides were identified in loam and silty sands in Søltuvík on the island of Sandoy, dated prior to AD 1000. Their formation is related to intensive podzolization and they take the form of the source woody vegetation. The sub-fossil material represents the first evidence for ferruginous rhizoconcretions in the Faroese archipelago.

Evidence of Bioerosive Structures in Quaternary Glaciomarine Sediments from Southwestern Iceland

ABSTRACT The Late Weichselian marine and glaciomarine sediments occurring in many places along the coast of Iceland are rich in invertebrate fossils, especially mollusks and barnacles. A diverse ichnofauna, constituted especially by bioerosional traces documenting the activity of predators and animals that use the host shell for attachment or the construction of dwellings, was identified at the localities of Ósmelur, Saurbær, and Brekkubakkar in southwestern Iceland. The ichnotaxa identified include Anellusichnus circularis (Santos, Mayoral, and Muñiz), Caulostrepsis isp., Centrichnus concentricus (Bromley and Martinell), Clionolithes isp., Finichnus peristroma (Taylor, Wilson, and Bromley), Finichnus isp., Sedilichnus asperus (Nielsen and Nielsen), Sedilichnus cf. excavatus (Donovan and Jagt), Sedilichnus gradatus (Nielsen and Nielsen), Sedilichnus smiley isp. nov., Sedilichnus ovalis (Bromley), Sedilichnus paraboloides (Bromley), Sedilichnus simplex (Bromley), and Sedilichnus spongiophilus (Müller).