Turbidite Channel-Levee and Lobe Evolution Around Active Salt-Related Folds
Lorna Strachan1, Martin Gee2, Rob Gawthorpe1, and Emmanuel Eseroghene Adiotomre1
1 University of Manchester, Manchester, United Kingdom
2 Universiti Brunei Darussalam, Tungku Link, Brunei
The evolution of a submarine channel-levee and lobe turbidite complexes around actively growing salt-related folds and faults has been investigated using shallow, sub-seafloor 3D seismic data from the Angolan continental margin. The data reveal complex slope topography dominated by anticline-syncline fold pairs related to salt movement, which formed synchronously with turbidite channel-levee and lobe complexes. A detailed study of the turbidite channel and lobe complexes, using voxel tracking, shows that they are highly sensitive sea floor morphology and evolve mainly by: 1] aggrading or incising in response to local gradient changes resulting from fold growth, 2] following local sea-floor slope and becoming locally deflected from the regional palaeoslope, and 3] developing depositional lobes in low gradient growth synclines. However, turbidite channels may also become 'fixed' where they are able to incise at the same, or higher, rate than relative fold uplift. In this situation, rather than becoming deflected they cut across the developing folds at a high angle. The relationship between channel sinuosity and gradient are quantified and basic flow parameters have been determined for the formative turbidity currents using deposit dimensions. An evolutionary model for the slope system has been developed reflecting changing palaeoslope topography driven by salt-related fold growth and the likely episodic, un-sustained nature of the formative turbidity currents.