Seismic reflection evidence for detachment polarity beneath a major accommodation zone, west-central Arizona

Abstract

Interpretation of reflection seismic data across a major accommodation zone in west-central Arizona shows that a uniform polarity detachment fault can extend beneath opposing polarity tilt-block domains. A dip line, which roughly parallels the extension direction, shows that the White Tank detachment fault extends beneath both the southwest-tilted Whipple-Camelback and northeast-tilted Vulture domains.Top-to-the-northeast mid-Tertiary displacement along this detachment fault was responsible for formation of the White Tank metamorphic core complex. A second profile, which is a strike line approximately perpendicular to the extension direction, intersects the dip line near the core complex in the southwest-tilted domain. Basement reflectivity on both profiles extends from the White Tank detachment or mylonitic front down to the base of the crust. Relations between the basement reflectivity, core complex, and upper-plate tilt blocks suggest that the White Tank detachment fault is the dominant detachment in the area. The accommodation zone that separates the opposing tilt-block domains consists of a crystalline-cored rollover anticline that formed above the White Tank detachment fault as two oppositely tilted half grabens developed above inwardly dipping, upper-plate listric normal faults. Southwestdipping normal faults associated with the northeast-tilted domain appear to sole directly into either the through-going northeast-dipping White Tank detachment or a minor southwest-dipping low-angle normal fault. This minor southwest-dipping lowangle normal fault either soles into the White Tank detachment or offsets it by no more than 3 km. This suggests that faults associated with the northeast-tilted Vulture domain are essentially antithetic faults in the upper plate of the White Tank detachment. This arrangement shows that a major detachment fault associated with a more regional tilt-block domain can extend beneath a sizable domain of opposite polarity. It also shows that the tilt direction of fault blocks is not always a good indicator of the dip of the dominant underlying detachment fault.

Orthogonal folding of extensional detachments: Structure and origin of the Sierra Nevada elongated dome (Betics, SE Spain)

“…Other authors have concluded, in contrast, that the formation of domal and basinal detachment faults is the result of the interference between two independent processes. Folds with hinges trending perpendicular to the direction of extension have been interpreted as having been formed by (1) reverse drag caused by movement over a structurally deeper detachment [ Spencer , 1984; Bartley and Wernicke , 1984; Gans et al , 1985; Davis and Lister , 1988; Brady et al , 2000]; (2) the formation of antithetic shear zones in the lower plate [ Reynolds and Lister , 1990; Kruger et al , 1998]; (3) movement along a flat‐ramp fault surface, producing fault bend folding [ John , 1987]; and (4) isostatic rebound due to tectonic denudation [ Rehrig and Reynolds , 1980; Spencer , 1984; Buck , 1988; Wernicke and Axen , 1988] inducing ductile flow in the lower [ Block and Royden , 1990] or in the middle crust [ Wernicke , 1992; Axen et al , 1995]. In the latter model, it has been proposed that folds trending perpendicular to the direction of extension developed through a “rolling hinge” mechanism in which rotation migrates through the footwall as it is progressively unroofed [ Buck , 1988; Hamilton , 1987; Wernicke and Axen , 1988; Bartley et al , 1990; Axen and Wernicke , 1991; Spencer and Reynolds , 1991; Wdowinski and Axen , 1992; Manning and Bartley , 1994; Axen et al , 1995; Lee , 1995; Axen and Bartley , 1997; Lavier et al , 1999].…”

A reconstruction of late Miocene to Recent transtension in the southwestern United States and northwesternmost Mexico

“…• Beikman, Haxel, and Miller (1995) • Dokka, Ross, and Lu (1998) • Dokka (1989) • Gray, Miller, Peterson, May, Tosdal, and Kahle (1985) • Grubensky, Haxel, and Demsey (1995) • Grubensky, Haxel, and Kock (1993) • Jennings (1977) • Kruger, Faulds, Reynolds, andOkaya (1998) • Mattick, Olmstead, andZohdy (1973) Richard (1992aRichard ( , 1992bRichard ( , 1992c • Sherrod and Tosdal (1991) • Spencer and Reynolds (1991) • Stewart (1998) • Walker, Black, Berry, Davis, Andrew, and Mitsdarfer (2002) • Wells and Hillhouse (1989) Depth to Basement • Oppenheimer and Sumner (1980) Terrane Boundaries • Anderson and Silver (1981) • Bowring and Karlstrom (1990) • Chamberlain and Bowring (1990) • Gray, Miller, Grubensky, Tosdal, Haxel, Peterson, May, andSilver (1987) • Silver (1964) • Silver (1968) • Wooden, Miller, and Howard (1988) • Wooden and Miller (1990) • Unpublished mapping and reconnaissance by John A. Dembosky Jr., Thomas H. Anderson, Jonathan A. Nourse, Erin Stahl, and Leon T. Silver…”

“…In areas where published information is unavailable or insuffi cient to constrain restoration, basin geometries (Kruger et al, 1998), combined with consideration of regional geologic strain markers (such as boundaries between provinces of Proterozoic rocks and terranes), seismic interpretation (Eberly and Stanley, 1978), and depth to basement studies (Oppenheimer and Sumner, 1980), are utilized. Closure of north-trending basins in the study area is based on the following assumptions:…”