--> Abstract: Analysis of Fault Segment Evolution in Oblique Asymmetric Rift Systems Using Analogue Models, by Elizabeth Baker and Ken McClay; #90078 (2008)

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Analysis of Fault Segment Evolution in Oblique Asymmetric Rift Systems Using Analogue Models

Elizabeth Baker and Ken McClay
Fault Dynamics Research Group, Royal Holloway University of London, Egham, United Kingdom

The analogue models presented incorporate advances in techniques including surface laser scanning, high resolution digital photography and fault analysis and 3D visualisations (using Traptester (Badleys Geoscience) and VoxelGeo (Paradigm)). These methods have allowed improvements in characterising 4D fault segment propagation and interactions. The scaled models simulate asymmetrical extension of the upper crust (dry sand) above a lower ductile crust (silicone polymer). Oblique rift extension is generated by varying the baseplate angles from 90° to 30° to the extension direction. The models are extended from one side (extending margin) to a maximum of 10 cm extension.

After 4 cm deformation, all extending margins display a broad zone with variable fault orientation (generally high angle strike to the extension direction), whereas the stationary margins forms a narrow zone with greater organisation and fewer faults. Central rift faults develop and link with neighbouring extending margin structures forming clusters of higher density short faults and relatively undeformed horst blocks. At the experiments end the stationary margin faults have remained organised, in contrast the faults on the extending margin have progressively decreased in activity resulting in migration of fault displacement towards the central rift structures. Central rift faults from orthogonal/ low angle rifts (> 60° trend) are hard linked to each other and baseplate aligned. Whereas higher angle oblique rifts (< 45° trend) form en echelon horst and graben features with fault linkage structures aligned with the baseplate.

With higher rift obliquity, faults have increasingly shorter segment lengths resulting in more complex fault interactions and linkages that have implications for sediment dispersal patterns and for trap formation as well as for fluid migration pathways during burial.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas