Geological coastal map of Lower Saxony 1: 25 000 — Relief of the Holocene Base

Today’s coastal area with its landscape features, the islands, wadding and marshes, is geologically a very young structure that has only emerged in the last 8500 years under the influence of a sea level rise of about 25 m. The originally existing geest landscape, formed in the Ice Age, was flooded, partially redesigned and covered in varying thicknesses by holocene coastal deposits. These are mostly clay-sluffy, sometimes sandy cotton and brackish water sediments, which are loaded into the coastal area by the sea and rivers, or peat which have been accumulated in coastal bogs. In the area of the islands, this up to 35 m thick sediment body is superimposed by dunes that reach up to 25 m in height. The Geological Coast Map of Lower Saxony 1: 25 000 presents the holocene landscapes and coastal deposits in two maps covering the following topics: — Relief of the Holocene Base — Profile types of the coastal holocene. The relief of the Holocene base is depicted in the form of a NN-related depth line plan, where the individual isolines mark depth levels of 1 m, while area colors summarise depth ranges of 2 m each. Map sections for which no statements can be made regarding the relief of the holocene base are characterised by light blue surface color. If a map sheet includes geest areas, these are displayed without surface color. In much of the coastal area, the Holocene base area corresponds to the former land surface formed in the Ice Age. In some places, however, this original relief was overstated by the holocene sea flooding and the associated erosion processes. Exposed parts of the original geest landscape were extensively removed under the influence of sea passage and surf, former valley systems were expanded by tidal currents, deepened and partly transformed into inland erosion channels. As sea level rise progressed, the original landscape forms and the areas redesigned in the Holocene were equally covered by young coastal deposits. Due to these conditions, the holocene base surface forms a geotechnically important interface between viable glacial moraine, meltwater and river deposits in the lying and repositionable holocene soft or loose deposits in the slope end.