Abstract
This paper describes an ongoing multidisciplinary study on the development of the barrier islands in the Danish Wadden Sea (Vadehavet), carried out by the Department of Geography and Geology at the University of Copenhagen and the Geolo gical Survey of Denmark and Greenland (GEUS). Nine sediment cores each c. 25 m long and a total of c. 45 km ground penetrating radar (GPR) profiles have been acquired on the islands of Rømø and Fanø. Geochemical and palaeontological analyses and dating of 150 core samples using optically stimulated luminescence (OSL) are in progress. This multidisciplinary approach has given new insights into the sedimentary architecture and development of the island, and the study is expected to result in a new detailed facies model. Such models are essential for an assessment of the effects of rising sea level associated with global warming. The new facies model can also be used as an analogue for subsurface oil or water reservoirs in similar sedimentary settings. This article presents selected core and GPR data from the Rømø barrier island.
Highlights
Juvre DybT07a-1 caused flooding of the peat swamp and formation of gytja, followed by lagoonal mud- and sand flats
The Rømø barrier island is situated in the northern part of the European Wadden Sea (Fig. 1)
Seven core wells were drilled on the island, and depositional units were defined on the basis of sedimentary structures, grain sizes, sorting, organic material, fossils, trace fossils and rootlets
Summary
T07a-1 caused flooding of the peat swamp and formation of gytja, followed by lagoonal mud- and sand flats. The fauna in the Rømø-4 well consists of small shells of the west coast fauna only. This suggests that the sand was deposited by washover events from the North Sea and that larger shells were left behind. About 11 m of medium-grained sand with numerous bivalve shells underlie the mud layer and are interpreted to have been deposited in a prograding to aggrading marine shoreface. 8 m of bioturbated heteroliths of sand and mud with numerous bivalve shells, especially Mytilus, and gastropods below the dam (Figs 2, 4). The heteroliths represent back-barrier lagoonal mud- and sand flats and overlie 3 m of sand-streaked mud with numerous bivalve shells. The peat layer was probably deposited during the initial Holocene sea-level rise.
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