Roy W. Schlische¹, Martha Oliver Withjack¹

(1) Rutgers University, Piscataway, NJ

ABSTRACT: Styles of Secondary Faulting and Folding Associated with Oblique Deformation

We used scaled experimental models to investigate two styles of oblique deformation. In the models, a cover sequence composed of wet clay overlies either a basement-involved, oblique-slip normal fault or a detached, oblique-slip normal fault. We also compared our results with published results from experiments with a cover sequence composed of dry sand.

The modeling results demonstrate that three styles of deformation can develop within the cover sequence above an oblique-slip normal fault. With partitioned deformation, dip-slip and strike-slip faults strike subparallel to the strike of the master fault. With focused deformation, oblique-slip faults strike subparallel to the strike of the master fault. With distributed deformation, an extensional forced fold develops above and parallel to the master fault. Numerous secondary normal faults cut the forced fold and strike obliquely to the master-fault strike. Distributed deformation gives way to focused or partitioned deformation as the displacement on the master fault increases, as the depth within the cover sequence increases, and as the thickness of the cover sequence decreases. With a basement-involved fault, the regional level of beds within the cover sequence changes across the master fault. With a detached fault, the regional level drops locally within an asymmetric graben above the master fault. Other notable modeling results include: 1) A single episode of oblique-slip faulting can produce two distinct fault populations with somewhat different trends and ages. 2) Fault patterns vary significantly with depth. Secondary faults become less oblique to the master-fault trend with increasing depth in the cover sequence.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado