Experimental Insights into the Origin, Geometry, and Evolution of Dip Domains and Transfer Zones in Extensional Provinces

Roy W. Schlische¹, Martha Oliver Withjack¹, and Amy Clifton^2
1 Rutgers University, Piscataway, NJ
² University of Iceland, 101 Reykjavík, Iceland

In many extensional provinces, large normal faults dip in the same direction, forming dip domains. Features named transfer faults, transfer zones, and accommodation zones (hereafter called transfer zones for brevity) separate adjacent dip domains. It is commonly assumed that transfer zones follow preexisting zones of weakness or that their orientation is systematically related to the extension direction. Experimental modeling provides insights into the origin, geometry, and evolution of dip domains and transfer zones and raises questions about the validity of the above assumptions.

In our scaled models, a homogeneous layer of wet clay overlies a rubber sheet that is stretched orthogonally or obliquely between two rigid plates. Dip domains and transfer zones develop in all models. These dip domains and transfer zones form spontaneously without any prescribed preexisting zones of weakness. The number of dip domains as well as the number and orientation of transfer zones are variable, even for identical models. Thus, the orientation of the transfer zones is not systematically related to the extension direction. We propose that dip domains develop because early-formed faults perturb the stress field, causing new nearby faults to dip in the same direction. As extension continues, faults from adjacent dip domains propagate toward each another. Because opposite-dipping faults ultimately interfere with each another in the zone of overlap, the faults stop propagating. Numerous smaller faults then form to accommodate the strain. The transfer zones result from the alignment of small faults and partially overlapping tips of faults from the adjacent dip domains.

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