Tunnel valley infill and genesis revealed by high-resolution 3-D seismic data

• Main Authors: Kirkham, JD, Hogan, KA, Larter, RD, Self, E, Games, K, Huuse, M, Stewart, MA, Ottesen, D, Arnold, NS, Dowdeswell, JA
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Society of America 2021
• Subjects: 37 Earth Sciences; 3709 Physical Geography and Environmental Geoscience; 3705 Geology; 13 Climate Action; Norway; Ice Sheet
• Online Access: https://www.repository.cam.ac.uk/handle/1810/327768; https://doi.org/10.17863/CAM.75223

<jats:title>Abstract</jats:title><jats:p>Landforms produced beneath former ice sheets offer insights into inaccessible subglacial processes and present analogues for how current ice masses may evolve in a warming climate. Large subglacial channels cut by meltwater erosion (tunnel valleys [TVs]) have the potential to provide valuable empirical constraints for numerical ice-sheet models concerning realistic melt rates, water routing, and the interplay between basal hydrology and ice dynamics. However, the information gleaned from these features has thus far been limited by an inability to adequately resolve their internal structures. We use high-resolution three-dimensional (HR3-D) seismic data (6.25 m bin size, ∼4 m vertical resolution) to analyze the infill of buried TVs in the North Sea. The HR3-D seismic data represent a step-change in our ability to investigate the mechanisms and rates at which TVs are formed and filled. Over 40% of the TVs examined contain buried glacial landforms including eskers, crevasse-squeeze ridges, glacitectonic structures, and kettle holes. As most of these landforms had not previously been detected using conventional 3-D seismic reflection methods, the mechanisms that formed them are currently absent from models of TV genesis. The ability to observe such intricate internal structures opens the possibility of using TVs to reconstruct the hydrological regimes of former mid-latitude ice sheets as analogues for contemporary ones.</jats:p> We thank bp, Harbour Energy, Equinor Energy AS, Lundin Energy Norway AS, Petoro AS, Aker BP ASA, Total E&P Norge AS and PGS for permission to publish images from the HR3D seismic data and the CNS MegaSurveyPlus. IHS and Schlumberger provided academic seismic interpretation software licenses. J.D.K. is supported by NERC grant NE/L002507/1.