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Abstract

The Ebbabreen ice−cored moraine area is covered with a sediment layer of up to 2.5 m thick, which mostly consists of massive diamicton. Due to undercutting by lateral streams, debris flow processes have been induced in marginal parts of this moraine. It was recognized that the sedimentology of deposits within the deposition area of debris flows is the effect of: (1) the origin of the sediments, (2) the nature of the debris flow, and (3) post−debris flow reworking. Analysis of debris flow deposits in microscale (thin sections) suggests a common mixing during flow, even though a small amount of parent material kept its original structure. The mixing of sediments during flow leads to them having similar sedimentary characteristics across the deposition area regardless of local conditions ( i.e. slope angle, water content, parent material lithology). After the deposition of sediments that were transported by the debris flow, they were then reworked by a further redeposition process, primarily related to meltwater stream action.
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Krzysztof Pleskot
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Abstract

Aeolian activity is common on ice free areas in regions with permafrost occurrence. Sparse high-Arctic tundra vegetation, modifying surface air flow and sediments transport, influences the generation of individual landforms and their assemblages. Observations were carried in central Spitsbergen (Svalbard), characterized by quasi-continental polar climate conditions with dry summers and common existence of winds velocities above loamy-sandy sediments transportation threshold. Dryas aeolian landforms created from aeolian material trapped by Dryas octopetala dwarf shrub were diagnosed. Main morphogenetic plants are accompanied by Saxifraga oppositifolia and Bistorta vivipara, rounded out with biological soil crust. Small size of semi-circular and semi-elliptic forms (0.25–0.85 m2) is related to low type of D. octopetala slowly growing on raised marine terraces. Aeolian sediments are characterised by low level of organic matter content. They exhibit diversified mineralogical composition resulting from variable petrography of source glacial and fluvioglacial covers. Eightpetal mountain avens are a dendroflora species composing phytocoenoses of plant communities related to the end stages of biocoenotic succession. Presented data indicate the reference environmental state for any research on plant cover response in the environment of aeolian activity during climate change.

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Authors and Affiliations

Janina Borysiak
Krzysztof Pleskot
Grzegorz Rachlewicz

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