Accelerator mass spectrometry (AMS) radiocarbon (14C) dating of Cerastoderma edule (Linnaeus 1767) and Mytilus edulis (Linnaeus 1758) shells sampled in AD 1889 near the island of Wangerooge gave a new local correction factor ΔR of −85 ± 17 14C years for the Wadden Sea area. The value is considerably higher than the available scattered data from the North Sea, which were obtained from pre-bomb growth rings of living Arctica islandica (Linnaeus 1767). This can be explained by the incorporation of 14C-depleted terrestrial carbon into the shell material which compensates the intensified exchange of CO2 between atmosphere and shallow coastal water, e.g. by tidal currents. Additionally, two examples of application of the new ΔR value in coastal research give deeper insights into the dynamics of bivalve shell preservation in the Wadden Sea and the need for further research to clarify the Holocene reintroduction of Mya arenaria (Linnaeus 1758) into European waters.

In the early 20th century, archaeological research in the terp (artificial dwelling-mound) region of the northern Netherlands focused, besides settlement history, on natural salt-marsh dynamics and sea-level rise. In particular Van Giffen used salt-marsh deposits under dated terp layers to reconstruct the rate of sedimentation of the developing salt marsh and relative sea-level rise.

This line of research in archaeology was rekindled during excavations in the terp of Wijnaldum-Tjitsma between 1991 and 1993. Since then, geology has become an integral part of archaeological research in the terp region. This paper focuses on the northwestern part of the province of Friesland (Westergo), where most archaeological terp research during the past three decades has been carried out, owing to several research programmes by the Province of Friesland. The primary aim of the geoarchaeological research is to better understand the interaction between human inhabitants and the salt-marsh landscape. The sedimentary record exposed in the excavation trenches makes it possible to collect data on the development of the coastal environments of the Wadden Sea prior to habitation, including data on sea-level rise. The sea-level data collected in the geoarchaeological studies in Westergo are the topic of this paper. The measured levels of the tidal-flat/salt-marsh boundary underneath the terps make it possible to reconstruct palaeo-Mean High Water (palaeo-MHW) levels. Such sea-level index points (SLIPs), based on marine shell data points from 12 locations, now make it possible to establish a palaeo-MHW diagram for this part of the Wadden Sea, for the period between 1200 BC and AD 100. In this period the palaeo-MHW in the Westergo region rose from c.1.8 m to 0.3 m −NAP: a mean sea-level rise of c.0.12 m per century.

We discuss the fact that elevation of the palaeo-MHW SLIP is not only determined by relative sea level (RSL), but also by the magnitude of the tidal amplitude. The tidal range, and therefore the MHW elevations in a tidal basin, can change from place to place and also in time. Also in a single tidal basin the tidal range is variable, due to the distortion of the tidal wave as a result of the morphology of the tidal system. Such local tidal range fluctuations – not related to sea-level rise – influence the palaeo-MHW curve of Westergo and other tidal basins in the Wadden Sea and need to be taken into account when interpreting the curve.

In this paper, we will go into the causes of changes in palaeotidal ranges in meso- and macrotidal systems, analyse the tidal range variations in recent and subrecent basins and estuaries and discuss the implications of these changes on the sea-level curve of the Westergo region in NW Friesland.

Palaeolandscape reconstructions at the German North Sea coast are essential for the understanding of coastal changes and dynamic landscape-forming processes. This study contributes to reconstructing Holocene coastal changes in the back-barrier area of the East Frisian island of Norderney and draws conclusions on the local palaeogeography. Five sediment cores were analysed in terms of sedimentology (grain-size distribution), geochemistry (TOC, TIC, N, C/N), microfauna (foraminifers and ostracods) and 13 radiocarbon dates. In order to identify driving environmental factors and support the facies interpretation, multivariate statistics (PCA) were carried out. Additional cores from the surrounding area (WASA Project and ‘Landesamt für Bergbau, Energie und Geologie’ (LBEG) Hannover) enabled correlation of the investigated cores over a transect of ~6 km, showing six depositional environments, which can be used for landscape reconstruction. Deposition starts with periglacial (aeolian and glaciofluvial) Pleistocene sediments, with subsequent pedogenesis followed by swamp conditions that develop into a salt marsh. The overlying tidal-flat sediments are partially cut by (fossil and recent) channel deposits. A hiatus at the base of the tidal-flat deposits that spans some 3000 years hints at their reworking caused by a combination of antrophogenic coastal protection measures and the impact of storms. Furthermore, based on the profile correlation and the age data, a widespread salt-marsh area with a minimum age of ~4000 cal BP is defined for the ‘Hohes Riff’ in the southwestern back-barrier of Norderney Island.

The ‘Wadden Sea Archive of landscape evolution, climate change and settlement history’ project (WASA) focuses on the analysis of marine sediment archives from the East Frisian Wadden Sea region. It aims at understanding the formation of palaeolandscapes since the end of the last ice age. One part of the project studies the possible correlation and shift of archaeological settlement patterns, climate change and sea-level rise through time in order to derive archaeological expectancy maps. In this paper we present our findings for a quantifiable set of Stone Age sites in the area of the prehistorical Dornumer tidal basin, discussing them against the background of coastal environmental factors and the applied methodology of our modelling. To enable spatial analysis of these sites, we developed a palaeographic elevation model, which was subsequently flooded at 2000-year intervals between the Boreal and early Subboreal periods. Particular challenges are posed by the dynamics of marine transgression, the related changes in the natural environment and their spatial extent. As a result of our GIS-based approach, the model can be extended geographically and provides a basis for future research.

The reconstruction of submerged palaeolandscapes and detection of settling surfaces along coastal zones became a major research topic within the last two decades. In this context, the WASA project made use of a multidisciplinary approach for defining the extension and describing the characteristics of the Late Pleistocene to Holocene deposits in the central Wadden Sea region. In addition to sub-bottom transects, more than 140 sediment cores were taken in such an area for stratigraphic reconstruction, making use of multi-proxy analysis. To harmonize these data with the existing regional core database (LBEG archive) a new core catalogue was developed, that allows the identification of the local Late Quaternary sedimentary sequences and their characteristic facies. The WASA core catalogue has been successfully applied for reviewing the published data about the stratigraphic sequence of the Wadden Sea, for a better definition in terms of stratigraphic sequences and spatial extent of the Quaternary geological evolution of the region, and for a detailed reconstruction of the coastal palaeoenvironments.

Within the multidisciplinary WASA project, 160 cores up to 5 m long have been obtained from the back-barrier area and off the coast of the East Frisian island of Norderney. Thirty-seven contained basal peats on top of Pleistocene sands of the former Geest and 10 of them also had intercalated peats. Based on 100 acclerator mass spectrometry (AMS) 14C dates and analyses of botanical as well as zoological remains from the peats, lagoonal sediments and the underlying sands, a variety of distinct habitats have been reconstructed. On the relatively steep slopes north of the present island, a swampy vegetation fringe several kilometres wide with carrs of alder (Alnus glutinosa) moved in front of the rising sea upwards of the Geest as it existed then until roughly 6 ka, when the sea level reached the current back-barrier region of Norderney at around −6 m NHN (German ordnance datum). From then on for nearly 4000 years a changing landscape with a mosaic of freshwater lakes and fens existed within this area. It was characterised by various stands of Cladium mariscus (fen sedge), alternating with brackish reed beds with Phragmites australis (common reed) and salt meadows with Aster tripolium (sea aster), Triglochin maritima (sea arrowgrass), Juncus gerardii (saltmarsh rush) as well as mudflats with Salicornia europaea (common glasswort). As far as shown by our cores, this highly diverse, and for humans potentially attractive landscape was at least some 4 km wide and followed the coast for about 10 km. Before the rising sea caused diversification of habitats, wet heath as well as dry and dusty sand areas existed. In the course of time, parts of the wet heath turned into raised Sphagnum bogs under an oceanic precipitation regime before this diverse landscape was drowned by the rising sea and finally covered by marine sediments, while the earlier sediments and peats were partly eroded and redeposited.

Sediment facies provide fundamental information to interpret palaeoenvironments, climatic variation, archaeological aspects and natural resource potentials since they are summary products of depositional processes, environmental conditions and biological activities for a given time and location. The conventional method of facies discrimination relies on macroscopic and/or microscopic determination of sediment structures combined with basic physical, chemical and biological information. It is a qualitative measure, depending on observer-dependent sedimentological descriptions, which cannot be reanalysed readily by further studies. Quantitative laboratory measurements can overcome this disadvantage, but are in need of large sample numbers and/or high temporal resolution, and are time-, labour- and cost-intensive. In order to facilitate an observer-independent and efficient method of facies classification, our study evaluates the potential of combining four non-destructive down-core scanning techniques: magnetic susceptibility (MS), X-ray computed tomography (CT), X-ray fluorescence (XRF) and digital photography. These techniques were applied on selected sections of sediment cores recovered around the island of Norderney (East Frisian Wadden Sea, Germany). We process and integrate the acquired scanning measurements of XRF elemental intensities, represented by principal components, MS, CT density and lightness of eight sediment facies previously recognised by conventional facies analysis: moraine, eolian/fluvial, soil, peat, lagoonal, sand flat, channel fill and beach-foreshore. A novel type of density plot is introduced to visualise the digitised sediment information that allows an observer-independent differentiation of these facies types. Thus, the presented methodology provides the first step towards automated supervised facies classification with the potential to reproduce human assessments in a fully reproducible and quantitative manner.

The Holocene sea-level rise has led to significant changes in present-day coastal zones through multifold retrogradational and slightly progradational displacements of the mainland coastline. During the course of this postglacial transgression, sediments characteristic of coastal environments accumulated first in palaeovalleys of the pre-Holocene landscape and later on the subsequently developed coastal plain. Based on a compilation of sedimentological, lithological and litho-chronostratigraphical data of more than 1200 sediment cores, we generated four palaeogeographic maps of the coastal zone of the central Wadden Sea to document with a high spatial resolution the landscape changes during characteristic phases of the Holocene sea-level rise, i.e. the periods 8600–6500 cal BP, 6500–2700 cal BP, 2700–1500 cal BP and 1500–1000 cal BP. Along three cross-sections, representing different hydrodynamic conditions and exposure, we exemplify how the Holocene landscape development and sedimentary facies types are controlled by the local palaeorelief, sea-level changes, sediment supply, accommodation space, the morphodynamic impact of channel shifts, and their erosion base. This leads to a better understanding of main factors controlling the local depositional processes of the coastal landscape along the central Wadden Sea during the Holocene transgression.

Pleistocene strata of the Wadden Sea region are mostly covered by an up to 10m thick sediment wedge deposited during the Holocene transgression. However, tidal inlets cut deep into the Holocene succession, causing Middle Pleistocene to early Holocene glacial and interglacial deposits to outcrop at the channel bottom. To investigate how the lithological properties and/or morphologies of these deposits affect the development of Holocene tidal inlets (e.g. limiting erosional processes), we analysed a series of eight cores to verify three high-resolution sub-bottom transects – and thus – to extend point-based data over a broader area. Furthermore, eight additional new cores (16 WASA cores in total), and 14 reinterpreted cores from the LBEG (Geological Survey of Lower Saxony) log database, were correlated to generate three short cross-sections at the transition from the tidal inlet (Riffgat channel) to the island of Norderney, revealing a number of new aspects for the reconstruction of the Pleistocene palaeoenvironments, i.e. the last two glacials (Saalian and Weichselian) and interglacials (Holsteinian? and Eemian). A succession of Middle Pleistocene lacustrine delta deposits, belonging either to the Holsteinian or the Dömnitz temperate stage, suggests the presence of Elsterian tunnel valleys located below the island. Furthermore, we verified the presence of an Eemian mixed tidal-flat system overlain by an Eemian sand tidal flat below the western head of Norderney which is, in contrast to suggestions from previous studies, not fully eroded in this area. Finally, we demonstrate that the Saalian moraine (Drenthe Main Till) functions as a limiting constraint in the vertical development of the Holocene/modern Riffgat channel. Our results provide a better understanding of the Quaternary stratigraphy of the central Wadden Sea as well as the influence of the subsurface geology on the architecture and evolution of tidal channels.

The 1717 Christmas flood is one of the most catastrophic storm surges the Frisian coast (Netherlands and Germany) has ever experienced. With more than 13,700 casualties it is the last severe storm surge with a death toll of this order. At the same time, little is known about the hydrodynamic conditions and the morphological effects associated with this storm surge.

In this study, 41 potential dyke failures in the Province of Groningen (Netherlands) associated with the 1717 Christmas flood were systematically reconstructed and mapped by using historical maps and literature and by analysing the recent topography in search of typical pothole structures and sediment fans. The dimensions of the sediment fans as derived from the topography show a good accordance with the dimensions documented by vibracore profiles, direct push tests and electrical resistivity tomography data taken at three fieldwork sites. Moreover, the fan dimensions closely agree with the dimensions as simulated using a process-based morphodynamic numerical model for one of the three sites, the village of Wierhuizen. Consequently, the recent topography is still indicative for the locations and dimensions of dyke failures and sediment fans associated with the 1717 Christmas flood. Considering the large number of detected dyke failures (41) and the large dimensions of the potholes and particularly of the sediment fans up to a few hundred metres wide and up to 0.7 m thick, this study proves significant morphological effects of the 1717 Christmas flood on the mainland of the Province of Groningen.

Based on the numerical simulation approach and the comparison with field data and field observations, a maximum seaward water level of 5 m NAP for the dyke failure at Wierhuizen during the Christmas flood can be derived. A similar maximum water level is indicated for the two other fieldwork sites Vierhuizen and Kohol, which is in good agreement with the maximum storm surge level of 4.62 m NAP historically documented for the city of Emden located almost 50 km to the east of Wierhuizen.

The results of the current study demonstrate that the reconstruction of historical dyke failures based on (i) historical sources, (ii) recent lidar/high-resolution topographical data, (iii) multi-proxy sedimentary field data and (iv) hydro- and morphodynamic numerical simulations is a highly promising approach to derive hydrodynamic conditions and the morphological onshore response of the 1717 Christmas flood in the Province of Groningen. This knowledge is essential to improve our understanding of extreme storm surge dynamics, their influence on the coastal landscape and the associated hazards for the coastal population.

Collecting sea-level data from restricted coastal areas is essential for understanding local effects on relative sea level. Here, a revised relative mean sea-level curve for the area of the East Frisian island Langeoog, northwestern Germany, for the time period from 7200 cal BP until Recent is presented. The revision is based on the reinterpretation of previously published and unpublished data following the HOLSEA standardisation of data handling. Altogether 68 sea-level data taken from 32 cores and outcrops from Langeoog, its back-barrier and the adjacent mainland, which have been collected since the 1950s for mapping and landscape reconstruction purposes, are presented. The age constraints, derived from radiocarbon ages of basal peat, intercalated peat and molluscs and optical dating of tidal deposits, were evaluated in terms of the HOLSEA sea-level protocol and their stratigraphic context. For 7200 cal BP until modern times, 30 sea-level index points with different uncertainty ranges were defined. Additionally, a factor of decompaction was estimated for the remaining basal peat samples as well as for the underlying sediments of intercalated peat samples.

The comparison of the Langeoog relative sea-level curve with the relative sea-level curve from the western Netherlands shows that the Langeoog curve lies up to 0.80 m lower than the Dutch curve and diverges for the time before 6000 cal BP. Though the offset coincides with the overall predicted trend of glacial-isostatic adjustment, it is less than predicted.

Our study provides a useful assessment of legacy data and contributes to an improved sea-level index dataset for the southern North Sea coast.