--> Abstract: Slope Instability and Its Impact upon the Fringe of a Deep-Water Sheet-Sand System: The Aptian Britannia Sandstone Formation, North Sea, by Simon P. Barker, Peter D. W. Haughton, William M. McCaffrey, Stuart G. Archer, and Bill Hakes; #90039 (2005)

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Slope Instability and Its Impact upon the Fringe of a Deep-Water Sheet-Sand System: The Aptian Britannia Sandstone Formation, North Sea

Simon P. Barker1, Peter D. W. Haughton1, William M. McCaffrey2, Stuart G. Archer3, and Bill Hakes4
1 University College Dublin, Dublin, Ireland
2 University of Leeds, Leeds, United Kingdom
3 University of Aberdeen, Aberdeen, United Kingdom
4 Britannia Operator Ltd, Aberdeen, United Kingdom

The lower Cretaceous Britannia Sandstone Formation is located close to the centre of the North Sea Triple Junction, UKCS. The upper part of the system comprises a series of thick (c. 3.8 to 16.5 m) extensively dewatered sandstone sheets that thin and pinch-out against a palaeoslope formed by the Fladen Ground Spur to the north. The sheets are here interpreted as the deposits of unusually large-volume, axially-dispersing turbidity currents, close to their run-out limit, which was 25-35 km southeast of the Britannia field. The fringes of the sheet sand system were locally unstable such that periods of failure alternated with periods of sand deposition. The remobilisation created an irregular base-of-slope topography with local relief estimated to exceed 15 m in some instances. Turbidity currents that subsequently flowed into the basin produced deposits that healed the failure-generated seafloor topography, markedly thickening into local deeps and thinning onto the palaeohighs.

Understanding of the processes of remobilisation and topographic healing gives important insights into the mechanisms of flow emplacement and thus the textural and facies variations within the deposit. This is important, as the Britannia succession has become a type section for the recognition of slurry flow facies, which predominate within the sheet sandstones along the northern fringes of the system. Many examples of internal bed fabrics represent the overprinting of original depositional slurry facies by the processes of syn- to post-depositional remobilisation. Thus the spectrum of slurry facies includes both depositional and post-depositional components, which vary systematically along transects normal to palaeoflow.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005