Coupling 3D
Numerical Modelling of Contractional
Structures, Sedimentation and River Network Evolution: The Stratigraphic
and Geomorphic Expressions of Fault-Related Fold
Bernal P, Asdrúbal J.1, Stuart Hardy2, Robert
Gawthorpe3 (1) PDVSA-Intevep,
Both drainage systems and syntectonic sedimentation responds to the interplay between
stratigraphic and tectonic processes in
three-dimensions. Current numerical techniques generally employ two-dimensional
cross-sections or non-lateral propagating 3-D structures to investigate syntectonic sedimentation in contractional
settings. In this study, the modelling of syntectonic sedimentation and river network evolution in
three-dimensional contractional structures is
achieved through use of a partial differential equation in a forward numerical
approach. Structural deformation in the transport direction is described by
fault-related folding and the rate of lateral growth is controlled by a scaling
relationship between fault width and maximum displacement.
Modelling results highlight the
differences between situations with lateral, including different fault scaling
laws, and non-lateral fold growth and suggest these can be recognised
by analysis of pre- and syn-tectonic strata and
drainage network geometries. Furthermore, analysis of two-dimensional
cross-sections can generally lead to equivocal and often erroneous
interpretation of deformation style. Low sedimentation compared to tectonic
rates and accommodation promotes offlap and onlap configurations as well as time transgressive
unconformities. In high accommodation scenarios, growth triangles within syntectonic sediments do not arise. In addition, modelling suggests that natural structure form when: (1)
the evolution of the fault is nonself- similar, or
(2) the fault grows as a result of thrust faulting events with similar
displacements along strike that are terminated abruptly at the fault tips. The
numerical models compare well to outcrop and subsurface data from natural
thrust systems and can be used as templates to aid interpretation of structural
geometry and kinematic evolution.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California