Timing and kinematics of deformation in the Cronese Hills, California, and implications for Mesozoic structure of the southwestern Cordillera

Regional and temporal variability of melts during a Cordilleran magma pulse: Age and chemical evolution of the Jurassic arc, eastern Mojave Desert, California

“…This deformation age bracket is consistent with the >148 Ma age for deformation suggested by Schermer et al (2001) and in a broader regional sense is consistent with the 169 to 154 Ma timing for deformation correlated with regional intra-arc thrusting in the East Sierran thrust system (Walker et al, 1990;Dunne and Walker, 2004).…”

“…In the northern east Mojave, the Fort Irwin sequence is composed of foliated diorite, quartz monzodiorite and granite that intruded along and outboard of the North American craton edge (Schermer et al, 2001). Compositionally similar foliated metaplutonic rocks with Middle Jurassic or older ages are exposed (1) to the south at Alvord Mountain and in the Cronese Hills Walker et al, 1990); (2) in the Granite Mountains, where Howard et al (1987;Young et al, 1992) described a foliated plutonic suite, intruded by relatively little-deformed diorite, quartz monzonite and granite; (3) in the Clipper Mountains, where Howard et al (1995;Gerber et al, 1995) described the Goldhammer pluton emplaced synchronous with intra-arc thrusting.…”

“…Contractile structures developed locally in concert with magmatism and may record a regional arc-fringing to intra-arc thrust belt reflecting arc-parallel contraction at relatively deeper structural levels (Walker et al, 1990;Dunne et al, 1998;Walker et al, 2002;Dunne and Walker, 2004).…”

“…In the specific case of the Jurassic arc, the timing of magmatism relative to intra-arc shortening and/or extension remains uncertain, as is the relationship between the arc and continental interior stratigraphic records, especially eolian sand sheets (Busby-Spera, 1988;Walker et al, 1990;Dunne et al, 1998;Dunne and Walker, 2004;Haxel and Miller, 2007). The exposed parts of the Jurassic arc in the Mojave Desert (Figure 1) record evidence of both extensional and contractile deformation that was broadly synchronous with magmatism, but it is unclear if this evidence indicates alternation of deformational style with time or with position in the arc infrastructure (Walker et al, 2002;Busby et al, 2002).…”

Structure and evolution of the East Sierran thrust system, east central California

“…Rock units and contractional structures strikingly similar to those associated with the Layton Well thrust fault crop out in the Granite Mountains [Davis and Burchfiel, 1973]. Farther southwest, contractional faults and related structures of Middle Jurassic age inferred to be correlative with the ESTS become more steeply dipping and strike northeast, as in the Cronese Hills [Walker et al, 1990] and, more speculatively, at Iron Mountain southwest of Barstow [Boettcher and Walker, 1993]. If these correlations are valid, then the locational controls for the ESTS must have changed, because these exposures of the ESTS trend SW obliquely across the arc.…”