INTERNAL DEFORMATION AND COMPACTION OF THE MAKRAN ACCRETIONARY WEDGE

The Makran accretionary wedge is one of the largest on Earth. A 7-km t hick column of sands and quartzolithic turbidites are incorporated int o this wedge in a series of deformed thrust sheets. We present the res ults of prestack depth migration and focusing error analysis (migratio n velocity analysis) performed on a profile across the Makran wedge. T he depth section shows the deformation style of the accreted sediments , and the migration velocities allow us to estimate porosity variation s in the sediments. The thrust sheets show evidence of fault propagati on folding, with a long wavelength of deformation (approximate to 12 k m) and secondary thrusting in the kink bands of the folds, such that t he central part of each thrust sheet is elevated to form an additional ridge. This deformation style and the 15 degrees steep surface slope of the first ridge suggest a high degree of consolidation. Porosities were calculated from the seismic migration velocities and the ratio of fluid pressure to lithostatic pressure lambda was estimated for 5 loc ations along the profile. Rather than being undercompacted and overpre ssured as in most accretionary wedges, the sedimentary input is normal ly compacted (exponential porosity decay) throughout almost the whole wedge. However, a slight increase in porosity and lambda at depth, wit h respect to the normal compaction curve indicates, that the turbiditi c sequence might be overpressured landward of the deformation front.