Seismic stratigraphic analysis of the Cenozoic sediments in the NW Faroe Shetland Basin – Implications for inherited structural control of sediment distribution
Introduction
Hydrocarbon exploration of Faroe Islands continental shelf started around 1994. Since then dense 2D and 3D seismic grids have been acquired covering the Faroese part of the Faroe-Shetland Basin and most of the Faroe Platform. In some areas the 2D seismic grid is dense, and the southernmost part of the Faroe-Shetland Basin is covered by 3D seismic data sets. 8 exploration wells have been drilled in the Faroe-Shetland Basin all located close to the UK border (Fig. 1).
Most of the previous studies regarding the post-basalt section in the Faroe-Shetland Basin are focussed on the south-eastern part of the basin. This article is concerned with the development of the Faroese part of the Faroe-Shetland Basin area through Cenozoic time with focus on the location of depocentres and sediment influx direction as the results of interplay between uplift, subsidence, inversion and reactivation of older structures by compression. Results from seismic interpretation of Early Eocene-Recent succession in Faroese sector of the Faroe-Shetland Basin are presented. Five seismic units of regional stratigraphic importance are identified within the study area and tied where possible to stratigraphic information from boreholes. For all five units the seismic character is described and structure and isopach maps are presented. The distribution of the individual Cenozoic units is compared with the location of Palaeozoic and Mesozoic structural elements (as outlined by Ritchie et al., 2011). From this comparison it appears that the location and outline of Cenozoic depocentres is guided by the pre-existing, Palaeozoic and Mesozoic structural elements.
Section snippets
Regional geological setting
The Faroe-Shetland Basin is a NE–SW trending basin located between the Shetland Islands and Faroe Islands. It developed as the result of several rift phases in Late Palaeozoic and Mesozoic times with the dominant basin forming faults being of NE–SW to N–S orientation (Doré et al., 1999; Roberts et al., 1999). This resulted in thinning of the crust to about 15 km along the axis of the Faroe-Shetland Basin (Bott, 1984; Hughes et al., 1998) and it has been suggested that the crust below the
Data
This study is based on interpretation of 2D (∼25,000 line km) and 3D (∼8000 km2) reflection seismic surveys acquired since 1994 in the Faroese part of the Faroe-Shetland Basin (Fig. 2). The dominant frequency and corresponding vertical resolution in the seismic data of the investigated post-basalt deposition is ranging from c. 47–86 Hz and 6.5–12 m (quarter-wavelength), respectively. The seismic data have been interpreted using the principles of seismic sequence stratigraphic analysis. Although
Sequence stratigraphy of the Eocene-recent succession of Faroe-Shetland Basin
The Eocene-Recent, post-basalt strata covers the Faroese part of the Faroe-Shetland Basin but thin out towards Munkagrunnur Ridge to the SW, Faroe Platform to the NW and Fugloy Ridge to the N (Figs. 1 and 4). Figure 3 summarize the stratigraphy of the Faroe-Shetland Basin, and illustrates correlation of stratigraphic units and surfaces used in this paper (Fig. 3, Column 4) with those used in previous studies (Andersen et al., 2000, 2002; Davies and Cartwright, 2002; Sørensen, 2003; Stoker
Discussion
The main sediment input directions into the Faroese part of the Faroe-Shetland Basin has shifted significantly through time, with Eocene being dominated by south to south-westerly sourced input while Oligocene to Recent mainly has a north to westerly source input (Figure 3, Figure 14, Figure 15, Figure 16). The various source input directions through Cenozoic time governed the locations of the depocentres (Fig. 16) from being in the centre of the basin in Eocene time to move farther towards the
Conclusion
During Cenozoic time a shift in sediment influx directions and location of depocentre take place in the Faroese part of Faroe-Shetland Basin which elucidate the tectonic development of the area.
Acknowledgements
The authors want to acknowledge Faroese Earth and Energy Directorate (Jarðfeingi), the Faroese Research Council, Statoil and ENI for funding this work which is a part of a PhD project. We also want to thank Martyn Stoker for pointing out that horizon T2d, which in the literature is believed to have a mid Mid Eocene age instead has an early Mid Eocene age and two anonymous referees for constructive review of the paper.
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