Tunnel valleys of the central and northern North Sea (56°N to 62°N): Distribution and characteristics

Abstract

The analysis of buried tunnel valleys in the North Sea can provide information about the past configuration and dynamics of the Scandinavian and British ice sheets and the processes by which sediment and meltwater were transported at the ice-sheet base. However, little is presently known about the distribution and characteristics of tunnel valleys in the Norwegian sector of the North Sea. Here we use an extensive database of 3D seismic and high-resolution magnetic data to map more than 2200 tunnel valleys in the Norwegian and British sectors of the North Sea between 56°N and 62°N. With the exception of the deep Norwegian Channel, in which evidence for tunnel valleys is absent, the geological setting of the North Sea is interpreted to have been conducive to tunnel-valley formation and preservation because of its poorly consolidated substrate and shallow water depths. The highest density of tunnel valleys is located in the central part of the North Sea where Quaternary sediments are thickest. The extreme length of some of the tunnel valleys, which are up to 155 km long, supports theories that tunnel valleys form in stages rather than catastrophically. Detailed analysis of the orientation of tunnel valleys and their relative age relationships within four representative subareas shows that tunnel-valley orientation varies significantly across the central and northern North Sea and between different generations of valleys. This suggests that the pattern of subglacial meltwater drainage in the central and northern North Sea was different between each deglacial event in which tunnel valleys were formed, which is in contrast to the southerly meltwater drainage route that is indicated by the generally north-south orientation of tunnel valleys in the southern North Sea.

GIS dataset: geomorphological record of terrestrial-terminating ice streams, southern sector of the Baltic Ice Stream Complex, last Scandinavian Ice Sheet, Poland

“…They often exceed 20 km in length, which is high (cf. Ottesen et al, 2020). However, their typical width below 2 km is conformant with counterparts of the Scandinavian Ice Sheet (cf.…”

“…Tunnel valleys are formed subglacially due to meltwater erosion either as a result of outburst floods or by a gradual or steady-state mechanism (Ó Cofaigh, 1996;Livingstone and Clark, 2016). The subglacial water flow is driven by gradients in hydraulic potential (function of the bed and ice elevation) (Shreve, 1972), resulting in orientations typically parallel to the glacier flow (Kehew et al, 2012).…”

Ice sheet and palaeoclimate controls on drainage network evolution: an example from Dogger Bank, North Sea

“…They broadly follow the protocol described by Ivanovic et al (2016), opting for a melt-uniform freshwater scenario that conserves water across the deglaciation in accordance with the prescribed ice sheets. Two sets of simulations were analysed; one uses the global ICE-6G_C ice sheet reconstruction (Peltier et al, 2015) performed at 1000year intervals from 26 to 21 ka and 500-year intervals from 21 to 0 ka (the same simulations are described in more detail by Morris et al (2018) in their Supplementary Materials and Methods), and the other uses the GLAC-1D global ice-sheet reconstruction (Briggs et al, 2014;Ivanovic et al, 2016;Tarasov et al, 2012Tarasov et al, , 2014Tarasov and Peltier, 2002) at 500-year intervals from 26 ka to present that are otherwise identical to the ICE-6G_C set. From these simulations, we extracted 50-year climate means for annual precipitation, total annual evaporation, and annual temperature for the 0.5 • × 0.5 • model grid square centred at 55 • N, 3.75 • E, which covers Dogger Bank.…”

Architecture of tunnel valleys in the southeastern North Sea: new insights from high‐resolution seismic imaging

“…Numerous studies have demonstrated the high abundance of tunnel valleys in the North Sea (Fig. 1a, Praeg, 2003; Kluiving et al ., 2003; Lonergan et al ., 2006; Kristensen et al ., 2007; Lutz et al ., 2009; van der Vegt et al ., 2012; Stewart et al ., 2013; Dove et al ., 2017; Prins and Andresen, 2019; Ottesen et al ., 2020). Few studies, however, have conducted research in the southeastern German North Sea sector between Helgoland and the Eider Valley (Lutz et al ., 2009; Winsemann et al ., 2020).…”