Flemish transgression
Flanders transgression is the ambiguous, inconsistently used term for a rise in sea level in the Holocene . In a broader sense, it stands for the global postglacial sea level rise in the entire Holocene (the Holocene was formerly called " Flandrian " in the English-speaking world ) and in a narrower sense for the older two phases of this Holocene sea level rise, which lasted until approx. 1000 BC. And is also known as the Calais transgression , as well as for the stratigraphic interval of the during this phase in the southern North Sea regiondeposited sediments. The term "Flemish Transgression" is therefore often avoided, at least in recent German-language literature.
Global warming about 12,000 years ago ushered in the end of the Vistula glaciation and the beginning of the Holocene. The melting of the continental ice sheets in North America and Europe as a result of the higher temperatures led to a rise in global ( eustatic ) sea levels, which also affected the North Sea region.
At the end of the Vistula Ice Age, the global sea level was more than 50 meters below today's level and large parts of today's southern North Sea were mainland. On the basis of palynostratigraphic and radiometric ( 14 C ) dating of marine Holocene sediments in the southern North Sea region, it was possible to prove that the sea level of the North Sea was between approx. 7750 BC. BC and 6000 BC Rose rapidly from 45 m below sea level to 15 m below sea level (mean high water), which corresponds to an annual increase of 1.7 cm. Around 6000 BC The coastline had advanced to the northern edge of today's West and East Frisian Islands.
Subsequently, the pace of sea level rise decreased and the today's coastal landscape of the North Sea with its extensive Wadden Sea was created : First of all, the rise in sea level raised the groundwater level in the former coastal landscape (" Palaeogeest "), which caused it to become wet, which in turn led to the accumulation of Peat led. The continued rise in sea then resulted in the deposition of powerful fine grained terrigenous, organikreicher Watt sediments ( clay ) which overlie the basal Torfhorizont. So-called floating peat horizons , which are connected to the up to 25 m thick Holocene wadden sediment sequence (they “swim” in the wadden sediments), represent phases of stagnation or a slight drop in sea level, during which the coastline could briefly advance seaward. The second of these 7 proven regressive phases took place between 1500 BC. BC and 1000 BC And is represented by one of the most striking and widespread peat horizons in the Holocene of the southern North Sea region, the so-called Upper Peat . It forms the end of the Flanders Transgression in the narrower sense, with the sea level at this point in time at around 2 m below sea level (mean flood). The subsequent, also slow sea level rise of the recent Holocene (from approx. 1000 BC), which takes place in cyclical bursts, is also known as the Dunkirk transgression .
Individual evidence
- ↑ R. Paepe, J. Sommé, N. Cunat, C. Baeteman: Flandrian, a formation or just a name? In: Newsletter on Stratigraphy. Vol. 5, No. 1, 1976, pp. 18–30 ( PDF 8.8 MB)
- ↑ a b c d Karl-Ernst Behre: A new sea level curve for the southern North Sea. Transgressions and regressions in the last 10,000 years. In: Problems of coastal research in the southern North Sea area. Vol. 28, 2003, pp. 9–63 ( PDF 15.4 MB)
- ↑ a b c d Karl-Ernst Behre: A new Holocene sea-level curve for the southern North Sea. In: Boreas. Vol. 36, No. 1, 2007, pp. 82-102, doi : 10.1111 / j.1502-3885.2007.tb01183.x
- ↑ a b c Friederike Bungenstock: The Holocene sea level rise south of the East Frisian island of Langeoog, southern North Sea - high-frequency sea level movements during the last 6000 years. Dissertation to obtain the doctoral degree (Dr. rer. Nat.) Of the mathematical and natural science faculty of the Rheinische Friedrich-Wilhelms-Universität Bonn. 2005, online