On the development of Holocene coastal barriers and beach systems (North Sea and Baltic Sea) - insights from OSL dating

Tony Reimann1, Sebastian Lindhorst2
1 Netherlands Centre for Luminescence dating, Faculty of Applied Sciences, Delft University of Technology
2 Institute for Geology and Palaeontology, University of Hamburg

V 6.4 in Quartäre Landschaftsentwicklung - ein Schlüssel zum Verständnis aktueller Georisiken

19.09.2012, 15:10-15:30, H8

Foredune ridges and swash bars are sensitive indicators of ancient shoreline positions and have thus significance for studies of Holocene coastal evolution. A basic requirement of a prograding beach or foredune plain is a positive sediment budged and furthermore a progressive vegetation cover to stabilise foredunes as well as the beach platform. A beach plain turn into an erosive mode for three main reasons: (i) a significant decrease in sediment supply, (ii) a significant relative sea-level, and (iii) regressive vegetation cover effectively reduces the quantity of sand being trapped at the beach. Hence, the development of Holocene coastal barriers and beach systems results from a complex interaction between variable environmental factors (e.g. sea-level, climate, geomorphology, land-use, coastal protection). The objective of this study is to correlate phases of prograding or erosive shorelines at the Baltic Sea and North Sea with past environmental changes. For this purpose, we re-analysed own data and other OSL chronologies of Holocene coastal sediment successions.

The chronologies of the investigated sedimentary archives indicate that under conditions of a fast sea-level rise (i.e. during the Littorina or Flandrian transgression) no established foredunes or swash-bars were formed. It is concluded that under conditions of an overall moderate sea-level rise (1.0-1.5 mm/yr) the setting of a beach system (progressive or erosive) is highly depending on other controlling parameters, in particular it depends on the relation of sediment supply, accommodation space and sediment trapping. The formation of foredunes and swash bars likely correlate with warmer, milder and calmer phases within the mid- to late-Holocene a stagnant or erosive beach plain correlate with well known phases of enhanced aeolian activity along the coasts of West and Northwest Europe in coherency with abrupt climate shifts to cooler and stormier conditions. Reasons for this observation will be discussed in the presentation.

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Letzte Änderung 25.07.2012