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-SEstriking 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.

The Salina del Fraile pull-apart basin, northwest Argentina

“…Such flower structure development is a common characteristic in the formation of strikeslip fault systems and does not require restraining oversteps or transpressional strain (e.g. Dooley & McClay 1996).…”

Aftershocks of the 2010 Mw 7.2 El Mayor‐Cucapah earthquake reveal complex faulting in the Yuha Desert, California

“…Previous studies suggest that complex surface faulting may become simpler at depth as faults coalesce onto prominent structures, so-called flower structures [Weldon II et al, 2002;Bozkurt and Koçyiôit, 1996;Wei et al, 2011]. Active flower structures have been observed along major well-developed strike-slip fault systems such as the southern San Andreas fault [Weldon II et al, 2002], along other major strike-slip fault systems in Southern California [Harding, 1985[Harding, , 1988Dooley and McClay, 1996], and along the North Anatolian fault [Bozkurt and Koçyiôit, 1996]. Conversely, it has also been shown that highly active, immature strike-slip fault systems may consist of parallel throughgoing fault strands, with secondary splays at varying orientations [Rybicki, 1973;Segall and Pollard, 1980;Reasenberg and Ellsworth, 1982].…”

Two-stage formation of Death Valley

“…Like the Black Mountains sections, these sediments show little evidence of syndepositional tec tonism, yet are now highly deformed, with almost vertical dips in places (Beratan et al, 1999). This deformation is associated with the Southern Death Valley strike-slip fault (Dooley and McClay, 1996) and gives a qualitative indication of the large amount of post-1.7 Ma motion there has been on this fault.…”