4D Structural Evolution of the West Niger Delta Deepwater Fold and Thrust Belt

Basil Tulbah

Research output: ThesisMaster's Thesis

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The thesis investigates the evolution of fold and thrust structures that occur in
the deepwater fold and thrust belt of the Niger Delta. The aim of the research is
to construct a 4D evolutionary model for one of the folds at the toe of the Niger
Delta to in order to understand the geometries and kinematics of the thrustrelated-
folding in the toe thrust belt.
Detailed seismic interpretation of 2D and a 3D depth-converted dataset has
been used to study the fold structures and growth-stratal geometries. Two main
folds occur in the survey area: the Aghar and Bobo folds. The Aghar fold is the
main focus of this research. It is 34km long and 6km wide, NW-SE trending
fold that creates up to 400m of seabed relief. The fold is highly asymmetric with
a steep dipping ~61-72° forelimb and less-steep dipping ~20-40° backlimb.
The fold is associated with a SW vergent thrust that cuts the forelimb, but is
non-emergent at the seabed. The thrust connects at the decollement in the
bottom of the section, and creates a ~40° ramp towards the middle of the
section. The detachment is interpreted to be an overpressured shale sequence.
The detachment unit thickens under the thrust by ~380m by brittle thrusting
mechanisms. In the middle of the forelimb, a mud volcano sits within a scarp
face ~16km long. Syn-kinematic units in the hanging wall side show fanning
geometries, where as the forelimb growth strata show self similar growth. This
departs from classic fault-bend and fault-propagation folds, and is more likely
represented by shear fault related fold models.
A ~2000m thick Paleocene to Eocene (?) pre-kinematic section has been
preserved. The Oligocene to Present Day (?) syn-kinematic section has fanning
geometries that thin from ~2000m to absent at the rest of the Aghar fold.
Thinning of the syn kinematic units began in the middle of the Aghar fold, and
rapidly progressed laterally, linking up several thrusts along strike. The middle
section is characterized to have a fold accommodation thrust the formed in the
forelimb at a shallower compared to the main ramp. The northern and southern
parts of the fold have a listric fault geometry with a backthrust complex.
The Aghar fold developed as a result of the joining of three faulted detachment
folds along strike, where the middle fold developed during the late Lower-
Miocene, and the northern and southern segments developed later in the Mid-
Miocene. The associated faults linked laterally to form the Present Day fold in
the Mid-to Late-Miocene. This evolutionary model probably occurs throughout
the Niger Delta and other passive deltas. The model provides insights on
brittle detachment development and the evolution of fault related folds in the
deepwater fold and thrust belt.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Department of Earth Sciences
  • Fault Dynamics Research Group
  • McClay, Ken, Supervisor
  • Elders, Christopher, Supervisor
Thesis sponsors
Award date1 Jul 2011
Publication statusPublished - 8 Jun 2011


  • Niger Delta
  • Fold-and-thrust belts
  • Gulf of Guinea

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