The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, the Faroes and Shetland Islands. So far, the German North Sea coast has been considered as being well protected due to the wide continental shelf and predominant shallow water depths, both assumed to dissipate tsunami wave energy significantly, thus hindering SST propagation dynamics. The objective of our research was to clarify if the SST reached the German Bight and if corresponding sediment markers can be found. Our research was based on the in-depth investigation of a 5 m long section of the research core Garding-2 from Eiderstedt Peninsula near Garding in North Frisia known from a previous study. For this, we newly recovered sediment core Garding-2A at exactly the same coring location as core Garding-2. Additionally, high-resolution Direct Push sensing data were collected to gain undisturbed stratigraphic information. Multi-proxy analyses of sediment material (grain size, geochemical, geochronological and microfaunal data) were carried out to reconstruct palaeoenvironmental and palaeogeographical conditions. We identified a high-energy event layer with sedimentological (e.g., erosional unconformity, rip-up clasts, fining-upward), microfaunal (e.g., strongly mixed foraminiferal assemblage) and other features typical of tsunami influence and identical in age with the SST, dated to ca. 8.15 ka cal BP. The event layer was deposited at or maximum ca. 1–1.5 m below the local contemporary relative sea level and several tens of kilometers inland from the coastline within the palaeo-Eider estuarine system beyond the reach of storm surges. Tsunami facies and geochronological data correspond well with SST signatures identified on the nearby island of Rømø. SST candidate deposits identified at Garding represent the southernmost indications of this event in the southeastern North Sea. They give evidence, for the first time, of high-energy tsunami landfall along the German North Sea coast and tsunami impact related to the Storegga slide. SST deposits seem to have been subsequently reworked and redeposited over centuries until the site was affected by the Holocene marine transgression around 7 ka cal BP (7.3–6.5 ka cal BP). Moreover, the transgression initiated energetically and ecologically stable shallow marine conditions within an Eider-related tidal channel, lasting several millennia. It is suggested that the SST was not essentially weakened across the shallow continental shelf of the North Sea, but rather caused tsunami run-up of several meters (Rømø Island) or largely intruded estuarine systems tens of kilometers inland (North Frisia, this study). We, therefore, assume that the southern North Sea coast was generally affected by the SST but sedimentary signals have not yet been identified or have been misinterpreted. Our findings suggest that the German North Sea coast is not protected from tsunami events, as assumed so far, but that tsunamis are also a phenomenon in this region.
The Quaternary of the northwestern part of Germany is characterized by several glacial periods, interglacials, glacial fluvial outwash, and glacio-lacustrine basins. The result is a complicated sedimentary fabric that varies from sediments of almost fluid consistency (ooze) over concrete-like tills to crystalline boulders, and this creates severe problems for tunnel construction. Aquifers too cause many problems. These geotechnical problems have forced construction engineers to develop new procedures and methods. The Hamburg-Elbe tunnel, situated on the west side of the city, was built on one of the most distinctive sites for an underwater tunnel. During its construction, many new techniques whose use depended on the variable geology were tested and applied. Detailed geological data were acquired during the excavation of the construction sites, which added substantially to our knowledge of glacial stratigraphy and glacial tectonics. The information thus acquired will be taken into consideration in future tunnel construction.
Abstract. The deposits near the surface of the Permian and Quarternary in the western part of the “Lieth lime quarry” have been intensively periglacially modified. Three ice-wedge pseudomorphs, which run approximately parallel, are 0.5 m wide and reach a depth of more than 3 meters. These features are of particular importance to periglacial science due to their setting in Zechstein-ashes and -limestones, their unusual size and their spatial relationship to several similarly large structures. Their development can be explained by geological factors. The fine-grained calcarious rocks, within which the wedges are developed, offer good conditions for intensive frost action, in a similar fashion to the exposed Zechstein rocks with their shallow overburden of quaternary material. An unusually large mechanical strength of the surrounding ashes compared with sedimentary rocks elsewhere in northern Germany favoured the emergence of larger structures. Spatial relationships, similar dimensions and orientation of the three large ice wedge pseudomorphs point to a connection with salt-tectonic structures. The structure of the latter had a considerable impact on the overall geometry of the ice wedges. Field relationships between structure, thickness, soil type and colour of individual fill units suggests two different phases of formation: A one-sided opening and backfilling appears to have taken place within two structures. The likely age of the reported structures possibly pre-dates the Weichselian glaciation.
Abstract. Während der Sanierung eines Raffineriegeländes in Wedel / Holstein wurden im Jahre 2008 auffällige Strukturen beobachtet. Die in Aufsicht polygonal verzweigten, rinnenartigen Strukturen sind in einen bindigen und kalkreichen, saalezeitlichen Till der Niendorf-Formation eingeschnitten und im Querschnitt symmetrisch halbkreisförmig ausgebildet. Die polygenetisch entstandenen Strukturen sind mit kalkhaltigen, schluffigen Sanden gefüllt, die als umgelagerter Till mit aus den hangenden Sanden vermischtem Material bzw. äolischen Komponenten interpretiert werden können. Die Breite der Strukturen beträgt ca. 0,3 bis 1,5 m, die Tiefe bis zu ca. 0,8 m. Bis zu mehr als 10 m lange Risse, als schmale Bänder rötlich gefärbter Sande ausgebildet, sind oft zentral in den o. g. rinnenartigen Strukturen positioniert. Die rötliche Färbung ist auf anthropogene Verunreinigung zurückzuführen. Diese Bänder reichen bis auf die Sohle der rinnenartigen Formen. An der Unterseite der Rinnenstrukturen setzen häufig glazitektonisch angelegte Klüfte an, die bis zu wenige Zentimeter breit sind und über mehrere Meter Tiefe bis an die Sohle der Auskofferung zu verfolgen waren. Die Genese der Strukturen, die einen möglichen Zusammenhang der rinnenartigen Strukturen mit dem glazitektonischen Kluftnetz bzw. den vermuteten paläohydrogeologischen Verhältnissen einschließt, wird diskutiert.
