Bulletin Article

We use three-dimensional seismic reflection data and new map-based structural restoration methods to define the displacement history and characteristics of a series of tear faults in the deep-water Niger Delta. Deformation in the deep-water Niger Delta is focused mostly within two fold-and-thrust belts that accommodate downdip shortening produced by updip extension on the continental shelf. This shortening is accommodated by a series of thrust sheets that are locally cut by strike-slip faults. Through seismic mapping and interpretation, we resolve these strike-slip faults to be tear faults that share a common detachment level with the thrust faults. Acting in conjunction, these structures have accommodated a north –south gradient in westward-directed shortening. We apply a map-based restoration technique implemented in Gocad to restore an upper stratigraphic horizon of the late Oligocene and use this analysis to calculate slip profiles along the strike-slip faults. The slip magnitudes and directions change abruptly along the lengths of the tear faults as they interact with numerous thrust sheets. The discontinuous nature of these slip profiles reflects the manner in which they have accommodated differential movement between the footwall and hanging-wall blocks of the thrust sheets. In cases for which the relationship between a strike-slip fault and multiple thrust faults is unclear, the recognition of this type of slip profile may distinguish thin-skinned tear faults from more conventional deep-seated, throughgoing strike-slip faults.
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We present a method of using fault displacement-distance profiles to distinguish fault-bend, shear fault-bend, and fault-propagation folds, and use these insights to guide balanced and retrodeformable interpretations of these structures. We first describe the displacement profiles associated with different end-member fault-related folding models, then provide examples of structures that are consistent with these model-based predictions. Natural examples are imaged in high-resolution two- and three dimensional seismic reflection data sets from the Niger Delta, Sichuan Basin, Sierras Pampeanas, and Cascadia to record variations in displacement with distance updip along faults (termed displacement-distance profiles). Fault-bend folds exhibit constant displacement along fault segments and changes in displacement associated with bends in faults, shear fault-bend folds demonstrate an increase in displacement through the shearing interval, and fault-propagation folds exhibit decreasing displacement toward the fault tip. More complex structures are then investigated using this method, demonstrating that displacement-distance profiles can be used to provide insight into structures that involve multiple fault-related folding processes or have changed kinematic behavior over time. These interpretations are supported by comparison with the kinematics inferred from the geometry of growth strata overlying these structures. Collectively, these analyses illustrate that the displacement-distance approach can provide valuable insights into the styles of fault-related folding.

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Explorer Article


Discoveries were comparatively sparse, but they persisted steadily throughout the year. Here are some of the more significant discoveries of the past year.

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A review of major oil and gas discoveries of 2013 shows a down year in terms of quantity—but that’s not the whole story.

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Explorer Emphasis


Oil should be a blessing. It creates jobs and puts food on the table for millions of people. It fuels the power that drives industrial growth and development to move countries beyond oil and gas into a sustainable future. That is how the first female president of NAPE views the hydrocarbons she has been working to discover since beginning her career 24 years ago.

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AAPG President Randi Martinsen and Africa Region President Dave Blanchard were scheduled to address the 32nd annual NAPE international conference and exhibition this past fall, but the trips were cancelled due to the Ebola virus outbreak in West Africa. Read the excerpts of the messages read by meeting officials on their behalf.

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Twenty years ago a formal message written on AAPG letterhead announced the beginning of a long relationship. Since the formalities of that early communication, two association leaders experienced an affiliation that has been mutually beneficial.

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Explorer Making a Difference

AAPG’s Publication Pipeline Committee recently had a small celebration to mark a very big accomplishment: Just a few weeks ago, the group officially topped the 100-ton mark of books, periodicals and other information that have been shipped around the world.
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Explorer Regions and Sections

Quiz time: When was the Nene Field, a 1.2 billion barrel field on the shelf in 90 feet of water, discovered?
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Since establishment of AAPG Africa in 2000, the Region’s leadership teams over the years have shown strong commitment and passion toward the Association achieving its goals for the region. Their dedicated efforts have resulted in not only an increased awareness of AAPG, but also steady growth of the Region’s membership, from 450 in 1999 to over 3,060 in June 2014.

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Short Course

Lagos Nigeria 22 February, 2016 24 February, 2016 21922
Lagos, Nigeria
22-24 February 2016
Sequence stratigraphy provides a framework for the integration of geological, geophysical, biostratigraphic and engineering data, with the aim of predicting the distribution of reservoir, source rock and seal lithologies. It gives the geoscientist a powerful predictive tool for regional basin analysis, shelf-to-basin correlation, and characterization of reservoir heterogeneity. This course will examine the underlying geological principles, processes and terminology related to sequence stratigraphic interpretation. The strength of this course is the application of these basic principles to subsurface datasets in a series of well-founded exercises.
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