Three-dimensional analyses of syndepositional faults and synkinematic sediments, Niger Delta, Nigeria
Final Report Abstract
Detailed structural and stratigraphic analyses of a 3D seismic volume of the shallow offshore Niger Delta document a considerable lateral variability in the style of syn-sedimentary normal faults and associated syn-kinematic strata within one tightly defined deltaic depocenter. This variability is due to the co-existence of tectonically stable, unfaulted areas, regions with significant landward subsidence that are segmented by medium- to large-scale normal faults, and terrain located above a major listric bounding fault that experienced major subsidence on both landward and seaward sides of a kilometerscale rollover anticline. Isopach maps document that least sediment accumulated on the stable, unfaulted terrain, more in the areas affected by medium- to large-scale faults, and most on both sides of the major deltaic rollover. The study area further exhibits a significant temporal variation in faulting during the studied interval that is expressed by the initiation, growth, decline and cessation of individual faults or fault segments. Maximum changes in stratal displacement and fault-length development are documented to occur primarily during the early growth phase of the studied faults. Once mature, most faults maintain their active length and displacement pattern with little variation unless linking with neighboring faults into extensive, multi-segment fault systems. The studied part of the Niger Delta is particular in that it exhibits at times a contemporaneous progression and backstepping of growth faults bounding one deltaic depocenter. This structural configuration is interpreted to reflect fault movement feeding back into sedimentary processes in form of a loop of cause-and-effect, monitoring on a local scale a deviation of the gross correlation between sediment loading and fault activity. It can be quantitatively documented that although on a large scale an apparent correlation with sediment loading exists, local-scale growth faulting remains an individual process that may act, irrespective of the regional sedimentary trend, out-of-sequence. The resultant development of local depositional sinks in a rather unexpected position of the system can produce sedimentary patterns that might oppose regional trends; this observation elucidates that sedimentary facies predictions based on system-wide, generalized depositional models are likely to overlook a significant part of the sedimentary detail stored in deltas.
Publications
- 2010. Analysis of gravity-driven growth faults and syn-kinematic deposition, Niger Delta, Nigeria. 4th French Congress on Stratigraphy, Abstract volume, p. 94-95
Fazlikhani, H. & Back, S.
- 2010. Deltaic growth faults and associated growth strata in the western Niger Delta, Nigeria. In: Tomás, S., Szurlies, M. & Mutti, M. (eds.), Sediment 2010. Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, v. 72, p. 32
Fazlikhani, H. & Back, S.
- 2010. Gravity-driven faulting and synkinematic deposition in deltas; a case study from the western Niger Delta, Nigeria. In: Hoppe, A., Röhling, H. & Schüth, C. (eds.), GeoDarmstadt 2010. Schriftenreihe der Deutschen Gesellschaft für Geowissenschaften, v. 68, p. 165
Fazlikhani, H. & Back, S.
