Strike-slip deformation in the Confidence Hills, southern Death Valley fault zone, eastern California, USA

Abstract

The Confidence Hills form a well exposed, composite, positive flower structure developed in Pliocene to Recent lacustrine and alluvial fan sediments. The structure has developed along the current trace of the southern Death Valley dextral strike-slip fault zone. California, USA. NW–SE-striking fault zones bound the Confidence Hills. In 3D, these fault segments are inferred to link at depth to a common basal fault system. The flower structure is formed by doubly plunging anticlines that roughly parallel the bounding fault segments. Fold development was aided by: (a) the presence of a basal salt deposit and numerous detachment horizons within the sedimentary pile and (b) buttressing and uplift along and against the bounding oblique-slip reverse faults. Structural and palaeomagnetic evidence indicates that the anticlines developed with axial surfaces parallel and sub-parallel to the trace of both fault zones. Folding appears to have initially developed adjacent to and above the southeastern fault segment and then propagated outwards and to the northwest. The latest displacements along the current southern Death Valley fault zone are probably only in the orders of hundreds of metres and as young as 0.9 Ma to Recent. This young fault zone is highly segmented along the length of the floor of southern Death Valley: the high proportion of oblique-slip faulting consistent with the strike-slip zone being immature. The Confidence Hills structure displays close geometric similarities with other natural examples of positive flower structures and to the features found in scaled. analogue sandbox experiments of strike-slip faulting.