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Abstract

Sedimentological study of the three geographically separated outcrops of bottom− sets of a single lava−fed delta (Pliocene) in the James Ross Island (Antarctica) allows recognition of six lithofacies. Deposits of traction currents, deposits of volcaniclastic debris flows and products of such flows transformations (both l ow− and high−density turbidity currents) and glacigenic deposits (subaqueous de bris flows and traction/turbidity currents) were all recognised. Existence of submarine proglacial environment formed prior to formation of volcaniclastic deposits partly covering the subaqueous slopes of volcano is supposed. The principal role of mass flow processes was recognised and explained by relative steep slopes of the lava−fed delta. The distribution of lithofacies significantly differs in the individual outcrops. These variations in sedimentary succession an d also in thickness of volcaniclastic deposits of “bottomsets” of the single lava fed delta suggest principal role of local conditions and paleogeography for development and preservation of this part of delta depositional system. Moreover proximal and distal setting can be followed and direct vs . more distant relation to over−riding lava−fed delta supposed. The sedimentary succession terminated by foresets of hyaloclastite breccia.
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Authors and Affiliations

Slavomír Nehyba
Daniel Nývlt
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Abstract

The Munin River (Svalbard) is a mountainous braided proglacial river. It drains from two valley glaciers developing an elongated channel belt and turning into a wide braided outwash fan before entering the main river. The Munin River is in its axial head supplied by the material from glaciers, and along the stream by material from lateral sources, i.e. braided outwash fan, debris-flow and fluvial-flow dominated fans. Detailed analyses of clast roundness showed that roundness suddenly changes to higher degrees in negative correlation with channel belt width and sinuosity of the channels. The roundness increases rapidly in sections with small channel belt width and low sinuosity, which can be seen in the bedrock gorge. On the contrary, the roundness does not change much in sections with large channel belt width and high sinuosity. The morphological changes of the channel belt are controlled by the bedrock morphology of the catchment, which is the main factor affecting the clast roundness in the Munin River. The nature of the lateral material sources and the downstream traction affect rather the individual gravel fractions.

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Authors and Affiliations

Lenka Ondráčková
Daniel Nývlt
Martin Hanáček
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Abstract

An accumulation of glacial sediments is located near Písečná village in the depression between the Sokol Ridge

and Zlaté Hory Highlands NNE of Jeseník town (Eastern Sudetes). The accumulation lies at the lateral side

of the mountain valley of the Bělá River and fills a preglacial palaeovalley of this river. Research combining

facies analysis of outcrops, ground penetrating radar survey, interpretation drilling survey, and modelling of

the preglacial relief was undertaken at the site. According to the results obtained, the upper part of the sedimentary

accumulation represents a coarse-grained terminoglacial glaciofluvial delta of the Gilbert type. The

development of the accumulation has dominantly been driven by the preglacial morphology. Facies typical for

foresets of coarse-grained deltas represented mainly by high-density flows, cohesionless debris flows, debris

falls and less common low-density flows were found in the outcrops. The delta near Písečná prograded into

a lake dammed by the ice-sheet front in the north. The lake was bounded by the slopes of Sokol Ridge, Zlaté

Hory Highlands and Góry Parkowe on other sides. The lake level reached an altitude of up to 430 m a.s.l., as

the coarse-grained delta plain base lies at this level.

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Authors and Affiliations

Martin Hanáček
Slavomír Nehyba
Daniel Nývlt
Zuzana Skácelová
Barbora Procházková
Zbynek Engel
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Abstract

The lakes and watercourses are habitats for various communities of cyanobacteria and algae, which are among the few primary producers in Antarctica. The amount of nutrients in the mineral-poor Antarctic environment is a limiting factor for the growth of freshwater autotrophs in most cases. In this study, the main aim was to assess the availability of mineral nitrogen for microorganisms in cyanobacterial mats in James Ross Island. The nitrate and ammonium ions in water environment were determined as well as the contents of major elements (C, N, P, S, Na, K, Ca, Mg, Al, Fe, Mn) in cyanobacterial mats. The molar ratios of C:N, C:P and N:P in mats were in focus. The growth of freshwater autotrophs seems not to be limited by the level of nitrogen, according to the content of available mineral nitrogen in water and the biogeochemical stoichiometry of C:N:P. The source of nutrients in the Ulu Peninsula is not obvious. The nitrogen fixation could enhance the nitrogen content in mats, which was observed in some samples containing the Nostoc sp.
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Authors and Affiliations

Pavel Coufalík
Daniel Nývlt
Petra Prochazková
Ondřej Zvěřina
Kateřina Trnková
Kateřina Skácelová
Josef Komárek

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