Rapid Quaternary subsidence in the northwestern German North Sea

Jashar Arfai,Dieter Franke,Jonas Kley,Lutz Reinhardt,Rüdiger Lutz,Christoph Gaedicke

doi:10.1038/s41598-018-29638-6

Jashar Arfai, Dieter Franke + Show 4 more

Open Access

https://doi.org/10.1038/s41598-018-29638-6

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Abstract

3D and 2D seismic data reveal the base-reflection of the Quaternary in the northwestern German North Sea locally at depths of more than 1000 m. This indicates extremely fast subsidence, with a rate of up to 480 m/Ma during the Quaternary, resulting in a NNW-SSE oriented sedimentary depocentre. Distinct iceberg scour marks, identified in 3D seismic data are used to calibrate quantitative subsidence analysis and to document shallow marine conditions during the Quaternary interglacials. Previously, a number of mechanisms have been proposed to explain the Quaternary subsidence. Here we show that compaction and load-induced subsidence alone explain about 75% of the observed Quaternary subsidence. However, a certain portion of the subsidence needs additional processes to be invoked. The extensive seismic dataset interpreted here makes it possible to exclude a phase of renewed tectonic activity as the origin of the subsidence anomaly. From the orientation and extent of the depocentre, lithosphere buckling and subsidence due to salt movement are considered unlikely. Possibly a post-glacial collapse after the retreat of glaciers in the North Sea Basin, local lower crustal flow, or dynamic topography or a combination of these processes contributed to the residual subsidence.

Highlights

Alongside the distinct offshore subsidence, onshore areas around the North Sea are subject to large-scale uplift[16,17,18,19,20,21]
In eastern Sweden, an isostatic uplift of about 310 m since the deglaciation of the last glacial maximum has been derived from Holocene shore displacement investigations by radiocarbon-dating[22]
It is suggested that the topography and landscape in northwestern England have almost entirely formed since the Middle Pliocene, accompanying ~800 m or more of uplift, while further to the south, total uplift since the Middle Pliocene has been estimated to be in the range of 150–200 m23,24

Summary

Introduction

Alongside the distinct offshore subsidence, onshore areas around the North Sea are subject to large-scale uplift[16,17,18,19,20,21]. It is suggested that the topography and landscape in northwestern England have almost entirely formed since the Middle Pliocene, accompanying ~800 m or more of uplift, while further to the south, total uplift since the Middle Pliocene has been estimated to be in the range of 150–200 m23,24 It is questionable if the uplift occurred during the Quaternary or before the Pleistocene[25,26]. The Quaternary sedimentary succession reaches a maximum thickness of more than 1000 m along a NNW-SSE trending basin axis in the central North Sea[33] (Fig. 1). Because most Quaternary sediments were deposited in a shallow-water environment[2,34], the southern part of the North Sea Basin must have locally experienced an extremely high rate of subsidence exceeding average Cenozoic rates by a factor of 10, as revealed by Cenozoic thickness maps[2,31,32]. The Quaternary North Sea Basin is characterized by three extensive glaciations, which covered large parts of the North Sea and adjacent land areas during the Pleistocene[35,36,37,38]

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