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Geo-Marine Letters

, Volume 38, Issue 5, pp 417–428 | Cite as

Enigmatic holocene sand ridges: complex meandering to anastomosing bedforms in the North Sea (German Seabight)

  • Vikram Unnithan
  • Angelo Pio Rossi
Original

Abstract

An intricate field of NNW-SSE trending sand ridges was discovered for the first time in 2010 and mapped in detail over the past 6 years during multiple campaigns in the vicinity of the islands of Helgoland and Dune in the German Seabight. The tramline-shaped, elongate, linear and meandering sand ridges are up to 1 km in length, over 10 m in height and spaced 10–50 m apart. The ridges exhibit complex anastomosing patterns, converging and disappearing to the south of the study area and diverging, becoming more subdued and disappearing further to the north. Seismic profiling, surface samples and multibeam data show that the ridges are stationary, while the sediment wave fields to the north and west are migrating westwards. Based on our mapping results, the most likely hypothesis for the development and maintenance of these enigmatic structures is a combination of tidal currents, tides and sediment influx. Whether these structures are associated with the Mesozoic subcrop or are glaciofluvial in origin and have been modified by the last glacial-interglacial intervals or are sedimentary structure linked to Holocene sea level rise in the southern North Sea is a matter of debate. Further studies, including numerical modelling of these sand ridges structures, would provide clues to past sedimentary and hydrodynamic conditions and future changes in the highly dynamic and complex tidal environment of the southern North Sea.

Keywords

Sand ridges German Seabight Enigmatic Meandering Multibeam Holocene 

Notes

Acknowledgements

The authors gratefully acknowledge the help and support of the Alfred Wegener Institute, Bremerhaven, Germany and in particular to Jelle Bijma for supporting, organising and coordinating the Oceanographic Student Excursions for the last 10 years. The captain and crew of the RV Heincke are thanked for their understanding and patience. Without them, and the countless undergraduate and graduate students who participated and helped acquire data during these excursions, this manuscript would not have been possible. In particular Rosa Crespo, who worked on the multibeam backscatter data as part of her MSc thesis. Finally, many thanks are due to two anonymous reviewers whose comments and suggestions significantly improved this manuscript.

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Jacobs University Bremen gGmbHBremenGermany

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