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| Titel |
Stress patterns of the Plio-Quaternary brittle deformation along the Calama-Olacapato-El Toro Fault, Central Andes |
| VerfasserIn |
F. Lanza, A. Tibaldi, G. P. Waite, C. Corazzato, F. Bonali, A. Nardin |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058422
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| Zusammenfassung |
| Understanding the geometry and kinematics of the major structures of an orogen is essential
to elucidate its style of deformation, as well as its tectonic evolution. We describe the
temporal and spatial changes in the state of stress of the trans-orogen area of the
Calama-Olacapato-El Toro (COT) Fault Zone in the Central Andes, at about 24Ë S within the
northern portion of the Puna Plateau between the Argentina-Chile border. The importance of
the COT derives principally from the Quaternary-Holocene activity recognized on some
segments, which may shed new light on its possible control on Quaternary volcanism and on
the seismic hazard assessment of the area. Field geological surveys along with kinematic
analysis and numerical inversion of ~ 280 new fault–slip measurements have revealed that
this portion of the COT consists mainly of NW-SE striking faults, which have been
reactivated under three different kinematic regimes: 1) a Miocene transpressional phase with
the maximum principal stress (Ïă1) chiefly trending NW-SE; 2) an extensional phase that
started by 9 Ma, with a horizontal NW-SE-trending minimum principal stress (Ïă3) –
permutations between Ïă2 and Ïă3 axes have been recognized at three sites – and 3)
a left-lateral strike-slip phase with an ~ ENE-WSW Ïă1 and a ~ NNW-SSE Ïă3
dating to the late Pliocene-Quaternary. Spatially, in the Quaternary, the left-lateral
component decreases toward the westernmost tip of the COT, where it transitions
to extension; this produced to a N-S horst and graben structure. Hence, even if
trascurrence is still active in the eastern portion of the COT, as focal mechanisms of
crustal earthquakes indicate, our study demonstrates that extension is becoming the
predominant structural style of deformation, at least in the western region. These major
temporal and spatial changes in the tectonic regimes are attributed in part to changes in
the magnitude of the boundary forces due to subduction processes. The overall
perpendicular-orogen extension might be the result of vertical stress larger than
both the horizontal stresses induced by gravitational effect of a thickened crust. |
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