HR: 08:15h
AN: T41F-02    [Abstracts]
TI: Thrust zone architecture and evolution in deep water sediments revealed by seismic reflection data
AU: * Butler, R
EM: butler@earth.leeds.ac.uk
AF: University of Leeds, Institute of Geophysics and Tectonics, Leeds, LS29JT, United Kingdom
AU: Paton, D
EM: d.a.paton@leeds.ac.uk
AF: University of Leeds, Institute of Geophysics and Tectonics, Leeds, LS29JT, United Kingdom
AU: Mortimer, E
EM: e.j.mortimer@leeds.ac.uk
AF: University of Leeds, Institute of Geophysics and Tectonics, Leeds, LS29JT, United Kingdom
AB: Commercial seismic reflection data from offshore west and SW Africa provide high resolution imagery of thrust zones. These structures have formed at the compressional toe-of-slope parts of 100s km –scale gravitational deformation systems. Two systems are contrasted; the Cretaceous gravity slide system of the Orange basin slope, and part of the active deep water thrust belt of the Niger delta (courtesy of data provided by CGG Veritas). The Orange examples involve c. 500ms TWT (c. 1 km) of sediment while the Niger examples involve about 2 km of pre-tectonic and a further 2 km of syntectonic sediment. In both examples seismic data reveal thrust ramp geometries (in 3D in the Niger case study). In the Orange examples thrust zones are narrow, with stratal reflectors retaining their amplitude up to their terminations. This indicates little heterogeneous distributed strain and the adjacent folding simply relates to fault geometry. In contrast, the Niger examples show trishear fault geometries with significant amplitude degradation into the thrusts. The thrust zones show soft relays along strike with polarity reversals. Although both case studies are formed in multilayer turbitide sand and mud systems, they differ in the extent of syn-deformation deposition. The Orange system was (locally) sediment starved so thrusts emerged onto the palaeo-seabed. The Niger system was continuously swamped by sedimentation. In these situations the thrust zones steepen upwards and do not activate upper thrust flats. Deposition exerted a profound control on fault and fold evolution, controlling thrust localization behavior in these sedimentary multilayers.
DE: 0905 Continental structures (8109, 8110)
DE: 3002 Continental shelf and slope processes (4219)
DE: 8005 Folds and folding
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting