TY - JOUR
T1 - Along-strike upper-plate deformation in response to metamorphic core complex emplacement, SE Arizona
AU - Wagner, Frank H.(Trey)
AU - Johnson, Roy A.
N1 - Funding Information:
We thank Randy Richardson, Bill Dickinson, Charles Ferguson, Jon Spencer and Robert Krantz for helpful discussions and insights. Two anonymous reviews also helped us in making improvements to the paper. We are grateful to ConocoPhillips and ExxonMobil for releasing the seismic data used in this study to the University of Arizona. Seismic processing and interpretation software were provided by Landmark Graphics Corporation through the Landmark University Grant Program. Funding for this project was provided in part by the National Science Foundation from grants EAR-8804667 and EAR-8817241. Financial support for F. Wagner was provided in part by ConocoPhillips, BP, ChevronTexaco, the University of Arizona Galileo Circle and from the H. Wesley Peirce Memorial Scholarship.
PY - 2010/6
Y1 - 2010/6
N2 - Metamorphic core complexes represent concentrated zones of crustal extension; universally, the hanging walls of these systems are extensively fractured, attesting to the significant horizontal extension above the evolving detachment zone. Recent analysis of a large grid of 2-D seismic reflection lines within the Tucson Basin of southeastern Arizona has facilitated a nearly three-dimensional interpretation of subsurface features related to Cenozoic crustal extension. Within the northern Tucson Basin, the Catalina detachment fault dips 23-35° to the southwest from the western flank of the Catalina/Rincon Metamorphic Core Complex. In the southern portion of the basin, the NE-trending Santa Rita normal fault dips 15-20° to the northwest from the western flank of the Santa Rita Mountains and is cut by the Catalina detachment beneath the central Tucson Basin. The orientation of the Santa Rita fault is problematical in that its orientation is nearly perpendicular to extension directions in the region, while geologic and seismic reflection evidence indicates that the Catalina detachment and Santa Rita fault were active synchronously. One possible explanation is that the Santa Rita fault is accommodating along-strike upper-plate deformation in response to core complex emplacement. To test this, we employed a finite-element modeling approach. A two-dimensional model consisting of a homogenous elastic material undergoing uniform extension is used to study changes in stresses and displacements in proximity to a zone of weakness representing a detachment fault in the upper crust. Away from the detachment fault, primary principal stresses are oriented parallel to the regional extension direction as expected. Near the detachment, extension in the system produces a rotation of the primary principal stresses of nearly 60° with respect to the regional stress field around the end of the fault. Additionally, the model predicts mechanical failure of the upper-plate of the detachment system to the south of the Catalina core complex. This model supports our interpretation that the orientation and early displacement noted on the Santa Rita fault is the result of a perturbation in the regional stress field caused by the Catalina detachment and the associated brittle failure of the upper-plate from the extreme crustal extension associated with core complex emplacement.
AB - Metamorphic core complexes represent concentrated zones of crustal extension; universally, the hanging walls of these systems are extensively fractured, attesting to the significant horizontal extension above the evolving detachment zone. Recent analysis of a large grid of 2-D seismic reflection lines within the Tucson Basin of southeastern Arizona has facilitated a nearly three-dimensional interpretation of subsurface features related to Cenozoic crustal extension. Within the northern Tucson Basin, the Catalina detachment fault dips 23-35° to the southwest from the western flank of the Catalina/Rincon Metamorphic Core Complex. In the southern portion of the basin, the NE-trending Santa Rita normal fault dips 15-20° to the northwest from the western flank of the Santa Rita Mountains and is cut by the Catalina detachment beneath the central Tucson Basin. The orientation of the Santa Rita fault is problematical in that its orientation is nearly perpendicular to extension directions in the region, while geologic and seismic reflection evidence indicates that the Catalina detachment and Santa Rita fault were active synchronously. One possible explanation is that the Santa Rita fault is accommodating along-strike upper-plate deformation in response to core complex emplacement. To test this, we employed a finite-element modeling approach. A two-dimensional model consisting of a homogenous elastic material undergoing uniform extension is used to study changes in stresses and displacements in proximity to a zone of weakness representing a detachment fault in the upper crust. Away from the detachment fault, primary principal stresses are oriented parallel to the regional extension direction as expected. Near the detachment, extension in the system produces a rotation of the primary principal stresses of nearly 60° with respect to the regional stress field around the end of the fault. Additionally, the model predicts mechanical failure of the upper-plate of the detachment system to the south of the Catalina core complex. This model supports our interpretation that the orientation and early displacement noted on the Santa Rita fault is the result of a perturbation in the regional stress field caused by the Catalina detachment and the associated brittle failure of the upper-plate from the extreme crustal extension associated with core complex emplacement.
KW - Catalina-Rincon metamorphic core complex
KW - Detachment fault
KW - Finite-element modeling
KW - Metamorphic core complex
KW - Santa Rita fault
KW - Stress rotation
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U2 - 10.1016/j.tecto.2009.07.017
DO - 10.1016/j.tecto.2009.07.017
M3 - Article
AN - SCOPUS:77953809310
VL - 488
SP - 162
EP - 173
JO - Tectonophysics
JF - Tectonophysics
SN - 0040-1951
IS - 1-4
ER -