Facies and development of a holocene barrier spit (southern Sylt/German North Sea)

Abstract

The aim of this ongoing study is the detection and interpretation of shallow subsurface on the German North Sea islands Sylt and Amrum using geophysical and sedimentological data. The main focus of the investigation lies on the reconstruction of the geological development of the southern barrier spit of Sylt, and the northern part of Amrum during the Holocene. The sedimentary structure and architecture of these island spit systems were investigated through an integrated approach using ground-penetrating radar (GPR) and sedimentological analyses of shallow sediment cores. Maximum penetration depths to 350 ns TWT which correspond to approximate depths of 15 m were reached. GPR surveys were orientated in 2D and 3D survey geometries with individual profile lengths between 30 m and 5 km. The topographic data of the GPR transects were collected by using a differential GPS. Different standard processing steps were chosen to increase the signal-to-noise ratio and to improve resolution. Until now, a total of 38 km GPR transects have been collected on the islands of Sylt and Amrum. To link GPR results with sedimentological data, 7 vibracores that reach a depth of 8 m below the surface were drilled at selected positions along the radar profiles. The combination of cores and high-resolution GPR data allows a detailed facies analysis and provides new insights into the complicated sedimentary architecture of the barrier island of Sylt and Amrum. Sedimentary architecture and internal structure of variety coastal elements has led to the definition and interpretation of different coastal environments as well as leads to new theories about the development of both barrier island spits.

Holozäne Landschaftsentwicklung an der Westküste der Nordseeinsel Amrum

“…Radarfazies Die Radarfazies Rf-AL-A1 umfasst einfallende kontinuierliche bis moderat kontinuierliche Reflektoren von mittlerer bis starker Amplitude (vgl. auch Tillmann & Wunderlich 2011a, 2011b, 2013. Die einzelnen Reflektoren sind zueinander parallel bis subparallel orientiert und besitzen ein steiles bis mittleres Einfallen (10°-30°) in unterschiedliche Richtungen.…”

“…Die Radarfazies Rf-AL-A3 wurde an keiner Stelle direkt durch Bohrungen durchteuft. Die Reflektoreigenschaften und Reflexionsgeometrien sowie der Vergleich ähnlicher Reflexionsmuster (Tillmann & Wunderlich 2011a, 2011b, 2013 lassen jedoch eine sandige Sedimentfazies vermuten.…”