Fault and fault-rock characteristics associated with Cenozoic extension and core-complex evolution in the Catalina-Rincon region, southeastern Arizona

Abstract

Cenozoic extensional deformation in southern Arizona included (1) a Neogene phase of Basin and Range deformation recorded by high-angle normal faults and (2)an earlier phase of detachment faulting and brittle-ductile crustal shearing associated with tectonic denudation of metamorphic core complexes. In the Catalina-Rincon region, exposed fault zones produced at different crustal depths during successive extensional episodes display differing fault geometries and types of fault rocks formed during progressive crustal extension. Detachment faults are associated with both mylonites produced by ductile shear and cataclasites produced by brittle shear. Younger faults formed at shallower depths are associated with less intense cataclastic deformation and with brittle fracturing that includes transtensile phenomena at the shallowest crustal levels represented. Qualitative measures of net displacement along individual fault zones are provided by (1) the nature of contrasts among successively overprinted fabrics and internal structures in the footwall and (2) the degree of contrast between fabrics and structures of footwall and hanging-wall rocks. Footwalls of the oldest structures display varied brittle overprints of ductile fabrics and are juxtaposed across gouge zones along detachment surfaces with stratal successions cut by multiple brittle shear surfaces. Footwalls † of younger structures formed at shallower depths display multiple generations of cataclastic features, including brecciation of variable intensity and cataclasite dikes, but are juxtaposed against hanging-wall strata that are only moderately deformed by subsidiary faults. The shallowest fault zones lack either structural overprints in their footwalls or any significant contrasts between footwall and hanging-wall deformation. Exposures of mid-crustal rocks within the core complexes reflect successive exhumation and uplift of fault footwalls during sequential episodes of deformation. The present high elevation of mylonitic rocks in the Catalina-Rincon metamorphic core complex reflects dip slip and isostatic footwall flexure during Basin and Range deformation as well as tectonic denudation during detachment faulting. Net uplift of core rocks resulted from multiple phases of deformation.

Active tectonics in the Sierra Nevada (Betic Cordillera, SE Spain): Insights from geomorphic indexes and drainage pattern analysis

“…2) has been considered as an orogenic dome or core-complex structure (Davis, 1980;Davis et al, 2004), having been exhumed since the Late Miocene in an extensional tectonic regime involving, in a first stage, both low-angle normal faulting and vertical ductile thinning (Galindo-Zaldívar et al, 1989;Martínez-Martínez et al, 2004). The Pliocene-Quaternary tectonic evolution is responsible for the formation of a large-scale open antiformal ridge coincident with the whole extent of the Sierra Nevada and coeval normal faulting (Fig.…”

Crustal versus mantle core complexes

“…faults, breccias, gashes…). These different types of fault rocks and their geometrical relations that characterize the detachment zones and their functioning have been first identified in the BRP and their origin understood thanks to some exceptional exposures like in southern Arizona (Davis, 1987;Davis et al, 2004).…”

Multistage Cenozoic extension of the Albion–Raft River–Grouse Creek metamorphic core complex: Geochronologic and stratigraphic constraints

“…1A), where they are typically intruded by synextensional plutons and bound by detachment faults associated with zones of very high ductile extensional strains (e.g., Coney, 1980;Wernicke, 1981;Armstrong, 1982;Miller and Gans, 1989). Regions fl anking metamorphic core complexes typically expose supracrustal rocks, including Cenozoic volcanic and sedimentary sequences that record the fi nal exhumation of the complexes (e.g., Eberly and Stanley, 1978;Dickinson, 1991;Davis et al, 2004;Miller and Gans, 1989;Miller et al, 1999;Colgan and Metcalf, 2006;Colgan and Henry, 2009).…”