Der holozäne Meeresspiegelanstieg südlich der ostfriesischen Insel Langeoog, südliche Nordsee : hochfrequente Meeresspiegelbewegungen während der letzten 6000 Jahre

In der vorliegenden Studie wird eine spätholozäne Meersspiegelanstiegskurve für das Gebiet der ostfriesischen Insel Langeoog in der südlichen Nordsee vorgestellt. Die Datenbasis besteht aus et-wa 600 Bohrungen, die freundlicherweise vom Niedersächsischen Landesamt für Bodenforschung in Hannover (NLfB) zur Verfügung gestellt wurden, etwa 68 km Boomer-Flachseismik, insgesamt 108 Pollen- und Radiokohlenstoff-Datierungen aus den Archivbohrungen des NLfB und 10 optischen Datierungen. Die Daten wurden mit der Methodik der Sequenzstratigraphie ausgewertet. Entlang der ostfriesischen Küste ist während des holozänen Meeresspiegelanstiegs ein keilförmiger Sedimentkörper akkumuliert. Er ist durch mehrere eingeschaltete Torfhorizonte im klastischen Sediment charakterisiert, die als Marker für Meeresspiegelbewegungen gelten. Eine Korrelation der Bohrkerndaten ist aufgrund der extrem kleinräumigen Fazieswechsel im Watt meist nur sehr unzureichend zu realisieren. Wie sich in den seismischen Messungen zeigte, bilden die eingeschalteten Torfe markante seismische Horizonte. Die Torfhorizonte konnten so zwischen den nur punktuell Information liefernden Bohrkernen verfolgt und in Bezug auf ihre sequenzstratigraphische Bedeutung ausgewertet werden. Es wurden nur die Torfe und die Datierungen derselben, die im Hinblick auf Meeresspiegelbewegungen als aussagekräftig herausgefiltert werden konnten, für die weitere Interpretation verwendet. Überlegungen zu den Genesebedingungen der Torfe und zum geometrischen Verlauf von Meeresspiegelbewegungen im Sinne von Niedrigstand-, Transgressivem und Hochstand-Systemtrakt (LST, TST und HST) haben ergeben, dass die Torfe für einen HST kennzeichnend sind. Die Meeresspiegelkurve bis etwa AD 800 verläuft somit stufenförmig und ist nicht durch Absenkungen gekennzeichnet. Für den letzten Abschnitt der Meeresspiegelkurve ab etwa 400 BC wurden neue Bohrungen abgeteuft. In diesem Zeitraum sind keine weit verbreiteten Torfe mehr in den Küstensedimenten zu finden. Die klastischen Sedimente konnten dennoch im Sinne der base-level Sequenzstratigraphie in transgressive und regressive Phasen untergliedert werden. Sie wurden für die optisch stimuliert Lumineszenz (OSL) beprobt. Der Abtrag der Datierungen in ein Zeit-Tiefen Diagramm zeigt für den Zeitraum von etwa AD 750-1000 eine Absenkung des Meeresspiegels. Der Vergleich sowohl des hauptsächlich auf sequenzstratigraphischen Überlegungen beruhenden Abschnitts der Meeresspiegelkurve, als auch des jüngsten auf den OSL Datierungen basierenden Abschnitts mit Kurven von benachbarten Küstenregionen zeigt ein gute Übereinstimmung

Calcium-Carbonat-Ausfällungen in einer Organomarsch

Während archäologischer Grabungen in der Marsch traten Konkretionen auf, deren Zusammensetzung und Entstehung untersucht wurden. Elektronenmikroskopische Element-Scannings zeigten, dass es sich bei diesen Konkretionen um Calcium-Carbonat-Ausfällungen handelt, mit höheren CaCO3-Anteilen im Kern als im Mantel. Die röntgendiffraktometrischen Untersuchungen bestätigten diese Ergebnisse und zeigten deutlich höhere Quarz-, Illit- und Kaolinitgehalte in der Hülle. Die Ursache der Carbonatausfällung ist in der besonderen Genese und Morphologie des Bodens mit schnellen und großen CaFreisetzungen während der Entwicklung aus einer PASS-Situation in eine AASS-Situation, dem präferenziellem Flow und einem undurchlässigen Untergrundhorizont zu sehen

Distribution pattern and controls of biosedimentary facies in backbarrier tidal flats of the central Wadden Sea (North Sea)

Facies analysis is a well-established tool in sedimentary geology, which allows the reconstruction of the depositional palaeoenvironment using sedimentological, ecological and geochemical proxies. Following an actualistic approach, we mapped the biosedimentary facies of a large backbarrier tidal flat system over a decade in the field covering four tidal basins with an area of 144 km(2). The spatial distribution of biosedimentary facies shows a complex pattern on a local scale, which superimposes the shore-normal energy gradient on a regional scale. The main controlling factors are hydrodynamic energy, the relative position to tidal channels, the duration of emergence, organism-sediment interaction and the presence of invasive species. Due to strongly fluctuating abundances of benthic organisms, the lateral extension of biosedimentary facies may differ significantly over the years. However, the grain size distribution reflects a more long-term equilibrium with the hydrodynamics of this coastal region. Additionally, we have documented a system shift of biogenic structures caused by the invasion of a non-native species, which functions as an ecosystem engineering species. Since we have focussed on tracemaking organisms, i.e., polychaetes and shell-bearing molluscs combined with abiotic parameters, the biosedimentary facies pattern of our study can be transferred into multidimensional facies analyses of sedimentary rocks deposited along ancient tidal coasts

Vertical and lateral distribution of Foraminifera and Ostracoda in the East Frisian Wadden Sea - developing a transfer function for relative sea-level change

In light of rising sea levels and increased storm surge hazards, detailed information on relative sea-level (RSL) histories and local controlling mechanisms is required to support future projections and to better prepare for future coastal-protection challenges. This study contributes to deciphering Holocene RSL changes at the German North Sea coast in high resolution by developing a transfer function for RSL change. Recent associations of Foraminifera and Ostracoda from low intertidal to supratidal settings of the barrier island of Spiekeroog in combination with environmental parameters (granulomeny, C/N, total organic carbon, salinity) were investigated and quantified in elevation steps of 15 cm in order to generate a first transfer function (TF) of Holocene RSL change. In a future step, the TF can be applied to the stratigraphic record. Our data show a clear vertical zonation of foraminifer and ostracod taxa between the middle salt marsh and the tidal flat with very few individuals in the sand flat area, suggesting removal by the tidal current or poor preservation. Multivariate statistics identify the elevation, corresponding to the inundation frequency, as main driving factor. The smallest vertical error (49 cm) is associated with an entirely new approach of combining Foraminifera and Ostracoda for a TF. Advantages of the TF over classical RSL indicators such as basal and intercalated peats - beside the relatively narrow indicative meaning - include the possible application to a wide range of intertidal facies and that the resulting RSL curve does not depend on compaction-prone peats

Fossil bog soils ('dwog horizons') and their relation to Holocene coastal changes in the Jade Weser region, southern North Sea, Germany

After the deceleration of the postglacial marine transgression, the German North Sea coast was subject to deposition of a complex pattern of subtidal to terrestrial facies. This study aims at reconstructing these facies changes in the 'Land Wursten' region (Lower Saxony) by focussing on so-called dwog horizons (incipient soil horizons of the pre-engineered salt marshes). We explore their implications for relative sea-level reconstructions and their indication for early settlement activities. Archive drilling data (1960, provided by the 'Landesamt fur Bergbau, Energie und Geologie') were analysed to create five high-resolution stratigraphic cross sections. Three new drilling records were subjected to sedimentological and microfaunal investigations and interpreted to verify and calibrate the archive data. Two dwog horizons were found and C-14-AMS dated. We found basal salt marsh deposits inundated by a high-energy event and covered by tidal flat sediments. The thick tidal flat unit is again overlain by salt marsh deposits indicating the transition from a shallow marine to a terrestrial environment where dwogs were developed and covered by episodic marine incursions. The ages of the dwogs (1128-969 cal BC; cal AD 1426-1467) do not correlate with known layers of adjacent settlement sites and are critically discussed. However, we show that they correlate with phases of stagnant regional relative sea level (RSL) and can be used as RSL indicators. The combined archive and modern data provide valuable information for the RSL reconstruction and palaeoenvironmental changes. However, further research is recommended to accomplish more detailed information about coastal response during the Holocene sea-level changes and implications for settlement dynamics

Documentation of sediment core WASA-N14

The core shows a sediment succession of the late Pleistocene and the Holocene. A core photograph is depicted, followed by a detailed core scetch and a depositional code for the depositional environment and facies. Sample locations for grain size, pollen, foraminifera, diatoms, macrobenthos, radiocarbon dating, XRD analysis and XRF data are marked in the columns right of the plot of the core. At the very right, the layers of the cores are described. The cores were taken in the central Wadden sea of the North Sea coast in the backbarrier tidal flat area of the Eastfrisian island Norderney/Germany within the frame of the multidisciplinary national research project 'WASA – Wadden Sea Archive', which has been undertaken to reconstruct submerged palaeo-landscapes in the central Wadden Sea. The project was running from 2016 to 2020 (Bittmann et al. 2022). Each of the three cores were collected in the subital with a modified version of the vibrocorer VKG6 (medconsultant GmbH) which was used from aboard the research vessels FK SENCKENBERG (Senckenberg am Meer, SaM, Wilhelmshaven) and BURCHANA (Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz, NLWKN, Norderney). The vibrocorer was deployed in full-weight load mode (1.1 t gravity weight) and was equipped with PVC liners of 5000 mm length maximum and 100 mm diameter. The cores were described based on the field proven core catalogue by Capperucci et al. (2022), which was developed on the base of all 140 cores taken in the area of Norderney within the WASA project. The core catalogue allows the identification of the local Late Quaternary sedimentary sequences and their characteristic facies and depositional environments of the Late Pleistocene and Holocene of the central Wadden Sea

Documentation of sediment core WASA-N11

The core shows a sediment succession of the late Pleistocene and the Holocene. A core photograph is depicted, followed by a detailed core scetch and a depositional code for the depositional environment and facies. Sample locations for grain size, pollen, foraminifera, diatoms, macrobenthos, radiocarbon dating, XRD analysis and XRF data are marked in the columns right of the plot of the core. At the very right, the layers of the cores are described. The cores were taken in the central Wadden sea of the North Sea coast in the backbarrier tidal flat area of the Eastfrisian island Norderney/Germany within the frame of the multidisciplinary national research project 'WASA – Wadden Sea Archive', which has been undertaken to reconstruct submerged palaeo-landscapes in the central Wadden Sea. The project was running from 2016 to 2020 (Bittmann et al. 2022). Each of the three cores were collected in the subital with a modified version of the vibrocorer VKG6 (medconsultant GmbH) which was used from aboard the research vessels FK SENCKENBERG (Senckenberg am Meer, SaM, Wilhelmshaven) and BURCHANA (Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz, NLWKN, Norderney). The vibrocorer was deployed in full-weight load mode (1.1 t gravity weight) and was equipped with PVC liners of 5000 mm length maximum and 100 mm diameter. The cores were described based on the field proven core catalogue by Capperucci et al. (2022), which was developed on the base of all 140 cores taken in the area of Norderney within the WASA project. The core catalogue allows the identification of the local Late Quaternary sedimentary sequences and their characteristic facies and depositional environments of the Late Pleistocene and Holocene of the central Wadden Sea

Documentation of sediment core WASA-VVC17

The core shows a sediment succession of the late Pleistocene and the Holocene. A core photograph is depicted, followed by a detailed core scetch and a depositional code for the depositional environment and facies. Sample locations for grain size, pollen, foraminifera, diatoms, macrobenthos, radiocarbon dating, XRD analysis and XRF data are marked in the columns right of the plot of the core. At the very right, the layers of the cores are described. The cores were taken in the central Wadden sea of the North Sea coast in the backbarrier tidal flat area of the Eastfrisian island Norderney/Germany within the frame of the multidisciplinary national research project 'WASA – Wadden Sea Archive', which has been undertaken to reconstruct submerged palaeo-landscapes in the central Wadden Sea. The project was running from 2016 to 2020 (Bittmann et al. 2022). Each of the three cores were collected in the subital with a modified version of the vibrocorer VKG6 (medconsultant GmbH) which was used from aboard the research vessels FK SENCKENBERG (Senckenberg am Meer, SaM, Wilhelmshaven) and BURCHANA (Niedersächsischer Landesbetrieb für Wasserwirtschaft, Küsten- und Naturschutz, NLWKN, Norderney). The vibrocorer was deployed in full-weight load mode (1.1 t gravity weight) and was equipped with PVC liners of 5000 mm length maximum and 100 mm diameter. The cores were described based on the field proven core catalogue by Capperucci et al. (2022), which was developed on the base of all 140 cores taken in the area of Norderney within the WASA project. The core catalogue allows the identification of the local Late Quaternary sedimentary sequences and their characteristic facies and depositional environments of the Late Pleistocene and Holocene of the central Wadden Sea

Insights into Holocene relative sea‐level changes in the southern North Sea using an improved microfauna‐based transfer function

In light of global warming and rising relative sea level (RSL), detailed reconstructions of RSL histories and their controlling processes are essential in order to manage coastal‐protection challenges. This study contributes to unravelling Holocene RSL change on the East Frisian North Sea coast in high resolution and with a new approach for the German Bight. For the first time, a transfer function (vertical error: 29.7 cm ≙ ~11% of the mean tidal range) for RSL change based on a combined training set of benthic foraminifers and ostracods from the back‐barrier tidal basin of Spiekeroog is applied to the Holocene record of the back‐barrier tidal basin of Norderney. The resulting RSL curve for the Norderney tidal basin is corrected for decompaction and shows a deceleration in RSL rise between 6000 and 5000 cal bp. The smallest possible error envelope (~1 m) results from the good suitability of salt‐marsh layers between 5000 and 4000 cal bp. The RSL curve provides an approach towards the closure of the common data gap of peat‐based curves for the southern North Sea related to a lack of basal peats in the youngest age range, and verifies regional differences in glacial isostatic adjustment.Volkswagen Foundation http://dx.doi.org/10.13039/501100001663Niedersächsisches Ministerium für Wissenschaft und Kultur http://dx.doi.org/10.13039/50110001057

Paleo‐Hydrogeological Modeling to Understand Present‐Day Groundwater Salinities in a Low‐Lying Coastal Groundwater System (Northwestern Germany)

Groundwater abstraction and drainage are considered to be the main drivers for the salinization of low‐lying coastal groundwater systems, while the role of past boundary conditions is less clear. In this study, 3‐D paleo‐hydrogeological variable‐density groundwater flow and salt transport modeling (“paleo‐modeling”) is applied to reconstruct the evolution of groundwater salinities during the Holocene, that is, the last 9,000 years, in Northwestern Germany. Novel aspects of this study include the consideration of highly resolved time‐variant boundary conditions in a 3‐D paleo‐modeling framework, for example, sea‐level rise, surface elevation and coastline changes, development of drainage networks and groundwater abstraction, as well as the quantification of isolated processes impacting salinization. Results show that salinization was a function of sea‐level rise from 9000 BP until 1300 CE. The creation of the dike line ∼1300 CE set the starting point for increasing anthropogenic control of the hydro(geo)logical system: changes in surface elevation and drainage of low‐lying marshes have become main drivers for salinization after 1600 CE when peat was artificially degenerated. Moreover, changes in the dike line caused by storm floods impacted the salinities. Model results for 2020 CE match well with present‐day salinity observations. Yet, salinization will continue in the future, as the hydro(geo)logical system has not reached an equilibrium. The presented paleo‐modeling framework can be viewed as a blueprint for similar low‐lying coastal groundwater systems, influenced by marine transgression and human development. Thereby, it enables the reconstruction of meaningful present‐day salinity distributions, serving as a vital basis for modeling future groundwater systems in a changing climate.Key Points: Salinization of a low‐lying coastal groundwater system during the Holocene, that is, 9000 BP until present‐day, was investigated. Sea‐level rise and the evolution of paleogeography were major controls on groundwater salinization during most of the time. Surface elevation changes due to land cultivation, as well as the development of drainage networks, control salinization since ∼1600 CE.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347https://doi.org/10.5281/zenodo.763338