--> Abstract: Salt Tectonic Controls on the Development of Normal Fault Systems: Insights from the Paradox Basin and Southern North Sea, by Nick Banbury and John Underhill; #90039 (2005)

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Salt Tectonic Controls on the Development of Normal Fault Systems: Insights from the Paradox Basin and Southern North Sea

Nick Banbury and John Underhill
University of Edinburgh, Edinburgh, United Kingdom

Contemporary models of normal fault growth and fault array development have been shown to be very effective in explaining the structural styles found in many classic rift settings. Observations of fault systems in numerous salt basins, however, reveal that faults developed in supra-salt sequences frequently show significant variability from established models.

Analysis of basin-scale, supra-salt normal faults in the Paradox Basin (Colorado Plateau) and Silverpit Basin (Southern North Sea) demonstrate the fundamental control that salt mobility has on the development of the fault systems. Fault systems in both basins have experienced extensive amounts of salt upwelling below the fault system during the faulting process and diapiric structures locally penetrate fault planes and behave as slip surfaces. Where this occurs, the style of displacement changes from dip-slip displacement with a significant vertical throw component, to heave-dominated horizontal stretching lubricated by upwelling salt. Relative amounts of footwall uplift and hanging wall subsidence vary significantly from faults in salt-free settings and whilst hanging wall subsidence can be small, footwall uplift appears to be significantly enhanced by salt mobility during faulting in these examples.

We conclude that in salt influenced structural settings, established concepts of the displacement-length scaling relationships of normal faults derived from observations of classic, salt-free rift basins begin to break down. Similarly the relationships between hanging wall subsidence and footwall uplift during faulting and therefore the development of fault controlled depocentres in salt influenced settings also show significant variability from established models.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005