Internal deformation and compaction of the Makran accretionary wedge
β Scribed by J. Fruehn; R. S. White; T. A. Minshull
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 509 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0954-4879
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β¦ Synopsis
The Makran accretionary wedge is one of the largest on Earth. A 7βkmβthick column of sands and quartzolithic turbidites are incorporated into this wedge in a series of deformed thrust sheets. We present the results of prestack depth migration and focusingβerror analysis (migration velocity analysis) performed on a profile across the Makran wedge. The depth section shows the deformation style of the accreted sediments, and the migration velocities allow us to estimate porosity variations in the sediments. The thrust sheets show evidence of faultβpropagation folding, with a long wavelength of deformation (ββ12 km) and secondary thrusting in the kink bands of the folds, such that the central part of each thrust sheet is elevated to form an additional ridge. This deformation style and the 15Β° 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 Ξ» was estimated for 5 locations along the profile. Rather than being undercompacted and overpressured as in most accretionary wedges, the sedimentary input is normally compacted (exponential porosity decay) throughout almost the whole wedge. However, a slight increase in porosity and Ξ» at depth, with respect to the normal compaction curve indicates, that the turbiditic sequence might be overpressured landward of the deformation front.
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