Abstract
According to a basic model, the formation of the coastal barriers in the southwestern Baltic can be divided into four evolutionary stages which are characterized by different rates of sea-level rise and varying relations between sediment supply and accommodation space. This model is tested using the example of a strandplain of the island Usedom, along with a local sea-level curve that reflects even smaller fluctuations of the water table and a detailed chronostratigraphy based on OSL measurements that allows the correlation of the morphodynamics with specific climatic phases. The resulting evolution scheme generally confirms the basic model but the timing of the stages depends on the inherited relief and has to be adjusted locally. A comparison with barriers from the W and SW Baltic region shows that the development during the past 5000 years was controlled by climate fluctuations which caused minor variations of the rather stable sea level and consequential changes in sediment supply, accommodation space and foredune deposition. Progradation decline can mainly be related to cool and windy climate phases which centered around 4.2, 2.8, 1.1, and 0.3 ka b2k, while increasing progradation correlated with warmer climate around 3.5, 2.0, and 0.9 ka b2k. The climate warming and the increasing sea-level rise in the recent past, however, led to shrinking progradation rates and may indicate a critical point beyond which the main progradation trend of the past turns into erosion.
Highlights
Along the coasts, climate-driven sea level and wind-field variations cause altering sediment supply, transport direction and accommodation space, and largely determine, together with the inherited morphology, the sediment budget of a particular coastal section (Beets and van der Spek, 2000)
The SW Baltic coast consists of cliff-faced Pleistocene headlands and Holocene sandy bay-mouth or lagoon-blocking barriers in between
Janke (1971) found that the transgressive dunes were deposited during the Little Ice Age (LIA), which is in accordance with our data we found an earlier beginning of the sedimentation
Summary
Climate-driven sea level and wind-field variations cause altering sediment supply, transport direction and accommodation space, and largely determine, together with the inherited morphology, the sediment budget of a particular coastal section (Beets and van der Spek, 2000). While a negative budget implies erosion and shoreline retreat, a positive budget causes net sediment deposition and is a precondition for the evolution of a coastal barrier. This paper exemplifies the barrier formation along the almost tideless, wave dominated, low to medium energy coast of the Baltic Sea of NE Germany. Due to the elongation of such spits and their coalescence barriers are formed which connect adjacent uplands and truncate lagoons from the sea. Ongoing net sediment accumulation causes the barrier shorelines to become progradational, forming strandplains with landforms such as beach ridges, dunes, inlets and wind-flats. The SW Baltic coast consists of cliff-faced Pleistocene headlands and Holocene sandy bay-mouth or lagoon-blocking barriers (terminology sensu Otvos, 2012) in between
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