Abstract
ABSTRACTOffshore stratigraphic records from the North Sea contain information to reconstruct palaeo‐ice‐sheet extent and understand sedimentary processes and landscape response to Pleistocene glacial–interglacial cycles. We document three major Middle to Late Pleistocene stratigraphic packages over a 401‐km2 area (Norfolk Vanguard/Boreas Offshore Wind Farm), offshore East Anglia, UK, through the integration of 2D seismic, borehole and cone penetration test data. The lowermost unit is predominantly fluviatile [Yarmouth Roads Formation, Marine Isotope Stage (MIS) 19–13], including three northward‐draining valleys. The middle unit (Swarte Bank Formation) records the southernmost extent of tunnel valley‐fills in this area of the North Sea, providing evidence for subglacial conditions most likely during the Anglian stage (MIS 12) glaciation. The Yarmouth Roads and Swarte Bank deposits are truncated and overlain by low‐energy estuarine silts and clays (Brown Bank Formation; MIS 5d–4). Smaller scale features, including dune‐scale bedforms, and abrupt changes in cone penetration test parameters, provide evidence for episodic changes in relative sea level within MIS 5. The landscape evolution recorded in deposits of ~MIS 19–5 are strongly related to glacial–interglacial cycles, although a distinctive aspect of this low‐relief ice‐marginal setting are opposing sediment transport directions under contrasting sedimentary process regimes.
Highlights
Throughout the Pleistocene, shallow continental shelves were periodically exposed and submerged in response to repeated glacial–interglacial cycles, respectively (Shennan et al, 2000; Bridgland, 2002; Busschers et al, 2007; Smith et al, 2011; Hijma et al, 2012)
This study aims to document a geologically constrained Middle to Late Pleistocene sedimentary sequence in the Vanguard wind farm zone offshore East Anglia, UK, using a densely spaced grid of 2D seismic reflection data, borehole
The Middle to Late Pleistocene sequence in the survey areas has been subdivided into four seismic units (L1–4) based on seismically mappable erosional surfaces/contacts (S1–4) that separate distinct seismic facies associations (Fig. 4)
Summary
Throughout the Pleistocene, shallow continental shelves were periodically exposed and submerged in response to repeated glacial–interglacial cycles, respectively (Shennan et al, 2000; Bridgland, 2002; Busschers et al, 2007; Smith et al, 2011; Hijma et al, 2012). Studies have highlighted periods of North Sea glaciation resulting in mapped ice‐sheet limits (Praeg, 1996; Scourse et al, 1998; Beets et al, 2005; Carr et al, 2006; Davies et al, 2011; Murton and Murton, 2012; Cotterill et al, 2017; Emery et al, 2019b), developed palaeogeographical maps (Funnell, 1996; Fitch et al, 2005; Hijma et al, 2012; Bicket and Tizzard, 2015) and reconstructed the evolution of north‐west European drainage networks (Gibbard, 1988; Bridgland and D'Olier, 1995; Peeters et al, 2015). In low‐relief continental shelf settings this assumption needs to be treated with caution This is true in ice‐marginal settings where major and abrupt change in sediment transport direction can occur, which complicates estimates of sediment flux and provenance studies. With sufficiently high‐resolution 3D data over large areas, sediment transport pathways can be mapped through time, leading to more meaningful palaeogeographical reconstructions, in low‐relief landscapes that have been subject to a complex changes in climate and base level over relatively short periods
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