The Response of Turbidite Slope Channels to Topography

Mike Mayall, Dave Hood, Keith Mills, Andrew Bowman, Roxanne Skeene, Lidia Lonergan, Stephen James, Tim Primmer, Louise Rogers
BP, Sunbury, United Kingdom

On many modern and ancient passive margin slope systems, complex and evolving sea floor topography is caused by active salt or shale diapirism and faulting. The slope topography significantly controls the distribution and nature of turbidite facies.
Turbidity currents and their deposits respond the topography in a wide variety of ways. When minimal topography is present, turbidite channels pass directly down the slope with only slight deflections. At the other end of the spectrum complex topography forming enclosed inter-slope basins causes ponding of sand on the slope.

Channel systems respond to evolving slope topography controlled by interplay of the erosional downcutting, rate of the topographic growth and timing of the development of the structure. When the erosion of the flows is strong enough and can overcome the rate of growth of the structure, channels can continue to incise across the growing structure. If the rate of growth of the structure is higher, the channel systems shift systematically sideways to avoid the rising topography. Earlier pre-existing, aerially limited structures causes the turbidite channels to take a sinuous course as they traverse the slope. Where early structures are more laterally extensive, channels may take extreme diversions, often kilometres along slope before continuing down the regional slope.

The geometry, internal stratigraphic architecture and the nature and distribution of the facies deposited within and around the channels is strongly controlled by the style of the sedimentation-topography interaction.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery