Landscape and Coast Development of A Lowland Fjord Margin Following Deglaciation, East Greenland
The landscapes of western Jameson Land bordering Hall Bredning fjord comprise upper river basins, glacial landscapes, lower river basins and a near-shore zone. The upper river basins are incised into bedrock and display no cover of young sediments whilst the glacial landscapes, located closer to the coast, are dominated by Pleistocene deposits and an irregular topography with hills and ridges. The lower river basins, dissecting the glacial landscapes, are connected to the upper river basins and contain well-defined Holocene delta terraces. The near-shore zone, which includes the present coast, displays a few raised shorelines. Geomorphological observations combined with stratigraphic work and 14C dates provide a chronological framework for the development of landscape and shoreline, as presented by a four-stage reconstruction. The first stage covers the deglaciation of western Jameson Land at the Weichselian-Holocene transition after a collapse of the main fjord glacier in Hall Bredning. The sea inundated the low-lying areas on Jameson Land forming small side-entry fjord basins that possibly follow the track of older valleys. This was followed by a second stage, the paraglacial period, when large meltwater production and sediment transport resulted in a fast infilling of the side-entry fjord basins by deltas. These are now exposed in terraces in the lower river basins at 70–80 m a.s.l. During a third stage, the relaxation period, fluvial activity decreased and the land surface was increasingly occupied by a cover of tundra vegetation. A glacio-isostatic rebound resulted in a relative sea level fall and fluvial incision. During stages two and three the coast was exposed to shallow marine processes that aided the alignment of the coast. Stages one to three presumably lasted for less than 2000 years. During stage four, the stable period, lasting for several thousand years till the present, there were minor adjustments of shoreline and landscape. The four-step reconstruction describes the sedimentary response of a lowland fjord margin to dramatic changes in climate and sea level. The distribution of erosion and sedimentation during this development was mainly controlled by topography. The reconstruction of the latest environmental development of Jameson Land puts new light on Jameson Land's long and complex Quaternary stratigraphic record. The reconstruction may also be used as a model for the interpretation of deposits in similar areas elsewhere.
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