Spatial and temporal variability of sediment accumulation rates on two tidal flats in Lister Dyb tidal basin, Wadden Sea, Denmark

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Anni Tindahl Madsen, Andrew S. Murray, Thorbjørn Joest Andersen, Morten Pejrup

Depositional processes in intertidal areas are determined both by changes in sea-level and sediment supply. It is known on a millennial timescale that sedimentation normally keeps pace with sea-level rise in a subsiding tidal basin. However, little is known about whether the sedimentation can keep pace with the rapid sea-level fluctuations that may occur on decadal or centurial timescales. Here, the sediment accumulation rates on two tidal flats in the Lister Dyb tidal basin (Wadden Sea, Denmark) are quantified in time and space in order to understand the interaction between changes in sea-level and sediment supply. Absolute chronologies, obtained using optically stimulated luminescence (OSL) and radiocarbon dating (14C), are presented from seven sediment cores. Forty-seven OSL ages, ranging between 6 ± 1 and 12 600 ± 900 years, were obtained. Six independent 14C age-estimates, ranging between 3800 ± 100 and 5620 ± 30¿cal. BP, support the OSL chronology. The absolute chronology allowed a description of the spatial and temporal variability of intertidal sediment accumulation rates across an aggrading tidal lagoon. On the mudflat in the western and sheltered part of the lagoon the intertidal sedimentation has followed the rate of relative sea-level rise, at least over the last ~2000 years, whereas the trends in sediment accumulation rates on the sandy tidal flat in the eastern and exposed part of the lagoon are less clear. Here, there is large variability in sediment accumulation rates and there may be patchy areas of erosion and accumulation. We conclude, however, that sediment accumulation on the two tidal flats in Lister Dyb tidal basin generally has kept pace with the rising sea-level. This conclusion seems to apply over the last few centuries and is generally true over the last few millennia. Furthermore, we conclude that sheltered mudflats appear to give the best description of how intertidal sedimentation responds to sea-level fluctuations.
Original languageDanish
JournalEarth Surface Processes and Landforms
Volume35
Issue number13
Pages (from-to)1556-1572
Number of pages17
ISSN0197-9337
DOIs
Publication statusPublished - Oct 2010

ID: 32432852