A morphometric analysis of tunnel valleys in the eastern North Sea based on 3D seismic data

Abstract

O. R. 2007. A morphometric analysis of tunnel valleys in the eastern North Sea based on 3D seismic data.ABSTRACT: A 1250 km 2 3D seismic volume is used to provide a detailed spatial and geometrical analysis of fifteen Pleistocene tunnel valleys in the Danish North Sea. All the valleys are buried; they are up to 39 km long, 3-4 km wide and up to 350 m deep. The valleys are part of a vast tunnel valley province covering an area of some 0.5 million km 2 of the formerly glaciated lowland areas of North West Europe. The valleys consist of non-branching, non-anastomosing troughs; they exhibit strongly undulating bottom profiles with numerous sub-basins and thresholds, and are characterised by adverse end slopes. Cross-cutting relationships and theoretical considerations suggest the occurrence of seven major episodes of valley incision attributed to ice marginal oscillations within a few glacials. Calculations considering the valley end gradients and theoretical ice-surface profiles suggest that the valleys were formed by pressurised subglacial meltwater erosion. Given a range of theoretical ice-surface profiles, the adverse end slopes are well beyond the supercooling threshold, which suggests that the water was not in thermal equilibrium with the basal ice and that flow was concentrated in substantial conduits with sufficient mass and flux to maintain water temperature well above the freezing point.

Morphological properties of tunnel valleys of the southern sector of the Laurentide Ice Sheet and implications for their formation

“…This is similar to tunnel valley widths (500-5000 m) reported in Europe and elsewhere in North America (e.g. Brennand and Shaw, 1994;Huuse and Lykke-Andersen, 2000;Jørgensen and Sandersen, 2006;Kristensen et al, 2007).…”

“…However, unlike elsewhere in the world few buried tunnel valleys have been reported along the southern margin of the Laurentide Ice Sheet, and most of the completely buried tunnel valley networks in Europe relate to pre-Weichselian ice advances (e.g. Jørgensen and Sandersen, 2006;Kristensen et al, 2007Kristensen et al, , 2008Stewart and Lonergan, 2011), so we suppose this problem to be minimal. Moreover, unless there is a systematic bias predisposing burial in some locations over others then the mapped pattern and distribution of tunnel valleys is likely to be informative.…”

Distribution, geometry, age and origin of overdeepened valleys and basins in the Alps and their foreland

“…The channels are up to 500 m deep, in some cases more then 150 km long (cf. Ehlers et al 1984;Huuse and Lykke-Andersen 2000;Stackebrandt 2009), and show to some extent cross-cutting relationships (Kristensen et al 2007). Palynostratigraphy indicates that the oldest phase of tunnel valley formation occurred prior to the Holsteinian (Fig.…”

Glaciogenic reservoirs and hydrocarbon systems: an introduction

“…Spectacular glacioterrestrial and glaciomarine successions occur across northern Europe, from the north European plains of Poland, Germany, Denmark, the Netherlands and eastern England (Ehlers et al 2011), and along the Atlantic continental margin (Dowdeswell et al 2002;Ottesen et al 2008Ottesen et al , 2012 through to the North Sea, where these glacial sequences are superbly imaged on highresolution 3D seismic data (e.g. Praeg 2003; Rise et al 2004;Graham et al 2010;Kristensen et al 2007;Buckley 2012). These seismic data facilitate the mapping of regional-scale, glaciogenic unconformities offshore , while the spectacular outcrops of well-preserved and welldated Pleistocene sediments onshore, in areas such as in western Denmark (e.g.…”