TY - JOUR
T1 - Cretaceous to Cenozoic sequential kinematics in the forearc-arc transition
T2 - Effects of changing oblique plate convergence and the San Andreas system with implications for the La Paz fault (southern Baja California, Mexico)
AU - Mattern, Frank
AU - Venzor, J. Antonio Pérez
AU - Espinoza, Jesus Efraín Pérez
AU - Rochin, Joel Hirales
PY - 2010/1
Y1 - 2010/1
N2 - We studied metasediments and mylonitic arc granitoids from the forearc-arc transition of southern Baja California, Mexico. Thin section analyses and field evidence show that metamorphism of the forearc-arc transition is of the high T/P active margin type. The heat was provided by Cretaceous arc intrusions. Field observations and thin section analyses, including the time/temperature deformation path, demonstrate that the study area was first affected by dextral, ductile shearing followed by ductile, sinistral, possibly transpressive strike-slip parallel to the magmatic arc during the Cretaceous. Both intervals are related to changing oblique plate convergence and, thus, identified as trench-linked strike-slip effects. The geometric relationship between arc-dipping foliation, stretching lineation and shear sense indicates that the arc may have been pressed onto the rocks of the study area during sinistral shearing. The sinistral interval lasted up until regional cooling (Early Cenozoic?). Because the La Paz fault is closely associated with the forearc-arc transition, it must have the same Cretaceous to Early Cenozoic kinematic history. The northern segment of the La Paz fault is a modern, brittle, strike-slip fault interpreted as a dextral synthetic fault of the San Andreas system which opened the Gulf of California (Mar de Cortés/Golfo de California). We found no evidence for Miocene Basin and Range extension.
AB - We studied metasediments and mylonitic arc granitoids from the forearc-arc transition of southern Baja California, Mexico. Thin section analyses and field evidence show that metamorphism of the forearc-arc transition is of the high T/P active margin type. The heat was provided by Cretaceous arc intrusions. Field observations and thin section analyses, including the time/temperature deformation path, demonstrate that the study area was first affected by dextral, ductile shearing followed by ductile, sinistral, possibly transpressive strike-slip parallel to the magmatic arc during the Cretaceous. Both intervals are related to changing oblique plate convergence and, thus, identified as trench-linked strike-slip effects. The geometric relationship between arc-dipping foliation, stretching lineation and shear sense indicates that the arc may have been pressed onto the rocks of the study area during sinistral shearing. The sinistral interval lasted up until regional cooling (Early Cenozoic?). Because the La Paz fault is closely associated with the forearc-arc transition, it must have the same Cretaceous to Early Cenozoic kinematic history. The northern segment of the La Paz fault is a modern, brittle, strike-slip fault interpreted as a dextral synthetic fault of the San Andreas system which opened the Gulf of California (Mar de Cortés/Golfo de California). We found no evidence for Miocene Basin and Range extension.
KW - Kinematic analysis
KW - La Paz fault
KW - Mylonites
KW - Oblique plate convergence
KW - Trench-linked strike-slip
UR - http://www.scopus.com/inward/record.url?scp=77952875555&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=77952875555&partnerID=8YFLogxK
U2 - 10.1007/s00531-008-0384-2
DO - 10.1007/s00531-008-0384-2
M3 - Article
AN - SCOPUS:77952875555
SN - 1437-3254
VL - 99
SP - 83
EP - 99
JO - International Journal of Earth Sciences
JF - International Journal of Earth Sciences
IS - 1
ER -