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Wet aeolian dune systems characterised by bedforms undergoing active construction and with interdune depressions that lie at or close to the water table are widespread on Skeiðarársandur, southern Iceland. The largest aeolian dune complex on the sandur covers an area of 80 km 2 and is characterised by four distinct landform types: (i) spatially isolated aeolian dunes, (ii) extensive areas of damp and wet (flooded) interdune flat with small fluvial channels, (iii) minor aeolian dune fields composed of assemblages of bedforms with simple morphologies and small, predominantly damp, interdune corridors, (iv) major aeolian dune fields composed of assemblages of complex bedforms up to 8 m high and floored by older aeolian dune deposits that are themselves raised up to 4 m above the level of the surrounding wet sandur plain. The morphology of each landform type reflects a range of styles of interaction between aeolian dune, interdune and fluvial processes that operate coevally on the sandur surface. Based on observations from a series of trenches, the geometry, scale, orientation and facies composition of sets of strata preserved in the cores of the aeolian dunes, and their relation to adjoining interdune strata, have been analysed to explain the temporal behaviour of the dunes in terms of their mode of initiation, construction, pattern of migration, style of accumulation and nature of preservation. The following interpretations are made: (i) seasonal and longer-term climatically-induced changes in water table level have caused episodic expansion and contraction of the wet interdune ponds, (ii) most of the dunes are currently undergoing active construction and migration and, although availability-limited because of the high water table, there must be substantial aeolian transport; much of this must occur during winter months when the surface of the wet interdune ponds are frozen and sand can be blown across ice sheets on the sandur without being trapped by surface moisture, (iii) bedforms within the larger dune fields have grown to a size such that formerly damp interdune flats have been reduced to dry enclosed depressions and dry aeolian system accumulation via bedform climb is ongoing, (iv) ongoing subsidence due to sediment compaction is progressively placing the aeolian deposits below the water table and is both enabling the accumulation of wet aeolian systems and increasing the likelihood of their long-term preservation.
Author(s): Mountney NP, Russell AJ
Publication type: Article
Publication status: Published
ISSN (print): 0037-0746
ISSN (electronic): 1365-3091
Publisher: Wiley-Blackwell Publishing Ltd.
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