Salt-marsh stratigraphy and late Holocene sea-level changes in Ho Bugt, western Denmark: implications for the ‘regional eustatic’ history of the North Sea Roland Gehrels1, Katie Szkornik1, Jason Kirby2, Glenn Milne3, Jesper Bartholdy4, Jørn-Torp Pedersen4, Jan Heinemeier5 and Wil Marshall1 1 School of Geography, University of Plymouth, UK Department of School of Biological & Earth Sciences, John Moores University, Liverpool, UK 3 Department of Geology, University of Durham, UK 4 Institute of Geography, University of Copenhagen, Denmark 5 Aarhus Radiocarbon Laboratory, University of Aarhus, Denmark 2 The evolution of salt marshes around Ho Bugt, the northernmost part of the Danish Wadden Sea, was investigated to establish a late Holocene sea-level history. This area is of interest as it is located near the ‘hinge line’ of isostatic stability between zones of isostatic uplift to the north and subsidence to the south. A sea-level history from this coast, therefore, is relevant for testing geophysical and empirical models of glacioeustatic sea-level change in the late Holocene. This is important for modellers of the glacio-isostatic adjustment process (i.e. Lambeck, Peltier and others) who are in disagreement about estimates of late Holocene ice melt. Furthermore, Ho Bugt sealevel data can be compared with a nearby sea-level curve for the Kattegat (between Denmark and Sweden) which has been proposed by Mörner (1969) to be representative of the regional eustatic sea-level history of the North Sea. Cores and exposed cliff sections were subjected to AMS14C dating and lithoand biostratigraphical (diatom) analyses to reconstruct the palaeoenvironmental history of the Ho Bugt salt marshes. Diatoms were sampled from the modern environment to establish their relationship with water levels (see Katie Szkornik’s abstract – this volume). Four stages in the development of the salt marshes can be identified: 1) groundwater table rise and growth of basal peat (from at least 4200 cal. yrs. BP to 2000 cal. yrs. BP); 2) initial salt-marsh formation (2000?-1700 cal. yrs BP); 3) a freshening phase (1700-800? cal. yrs BP), culminating in drying out of the marshes and producing a widespread very distinct black horizon; and 4) renewed saltmarsh deposition (800? cal. yrs BP to present), including a phase of aeolian sand deposition possibly related to dune building in the 17th century. From 18 AMS radiocarbon ages on fossil plant fragments we reconstructed a preliminary local sea-level history. Sea level has risen 3 metres since ca. 4000 cal. yrs BP and reached present mean sea level around 1500 cal. yrs BP. A sea-level fall of several decimetres is not well constrained by dates but occurred after 1500 cal. yrs BP. The Esbjerg tide-gauge record shows that sea level has been rising at a mean rate of 1.1 mm/yr since 1890. The Ho Bugt sea-level history does not support the Kattegat sea-level of Mörner (1969) and the late Holocene ‘regional eustatic’ significance of this curve is questionable. When isostatic factors are taken into consideration, late Holocene sea-level changes in Ho Bugt are in line with those documented in northern Germany.