Seafloor expression and shallow structure of a fold-and-thrust system, Isfjorden, west Spitsbergen

Abstract

A detailed map of the structure of the west Spitsbergen fold-and-thrust belt in the Isfjorden area, Spitsbergen, is presented. The map was constructed from a dense grid of two-dimensional multichannel reflection seismic and bathymetric data. Joint interpretation of two data sets allowed a comparison of tectonic structures detected along the uppermost parts of the seismic sections and those reflected in the morphology of the seafloor. Three major, predominantly north-west–south-east striking faults were identified. The westernmost fault (T1) is a hinterland-directed (most likely out of sequence) thrust, while the central and easternmost faults (T2 and T3) are foreland-directed (in-sequence thrusts). The thrusts divide Isfjorden into three subareas. Subarea 1 is bounded by thrust faults T1 and T2 and comprises Tertiary rocks surrounded by Jurassic–Cretaceous strata. The structural signature of Subarea 1 is that of a system of hinterland- and foreland-directed thrust faults, resulting in a seafloor relief characterized by parallel ridges and troughs. Subarea 2 is limited by thrust faults T2 and T3 and shows Jurassic–Cretaceous outcrops on the seafloor. Subarea 3 is situated east of the main thrust fault T3 and mainly involves outcrops of Triassic–Jurassic rocks. Together, Subareas 2 and 3 are dominated by foreland-directed, north-west–south-east and NNW–SSE-striking thrusts that are hardly detectable in bathymetric data.

• Svalbard
• Isfjorden
• west Spitsbergen fold-and-thrust belt
• seismic interpretation
• seafloor morphology
• shallow structures

Acknowledgements

We are grateful to the Norwegian Petroleum Directorate (NPD) for financial support. In particular, we thank Harald Brekke (NPD) for his assistance. We also would like to thank Statoil, participants of the Svalex expeditions, the crew of the RV Håkon Mosby and engineers from the Department of Earth Science at the University of Bergen (UB) for supplying geophysical data. Furthermore, we thank the Russian marine geological prospecting company Sevmorgeo for help with seismic data processing. We acknowledge the help of Ole Meyer and Bent Ole Ruud (UB) in analysing seismic and navigational data, Haflidi Haflidason and Berit Oline Blihovde Hjelstuen (UB) for contributing bathymetric data and Brian Robins for language editing.