Publication: Alpine paleostress reconstruction and active faulting
in western Iberia
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Publication Date
2010-05-07
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Abstract
The study of intraplate tectonics is crucial for understanding the deformation within plates, far from active plate
boundaries and associated stress transmission to the plate interiors. This paper examines the tectonic evolution
of the Variscan basement at the western margin of the Cenozoic Duero basin. Located east of the Vilariça
Fault System in NW Iberia, this intraplate zone is a relatively flat but elevated area with an intense NNE-SSW
trending fault system and associated moderate seismicity. Although the area has played an important role in
the Duero basin configuration, its Alpine to present-day tectonic evolution has not been well constrained.
In order to characterize the successive paleostress fields, 1428 pairs of fault-striae were measured at 56 sites
and two focal mechanisms were used. Stress inversion methods have been applied to analyze paleostress
regimes. Results show the existence of three dominant maximum horizontal stress (Shmax) trends: N-S,
NE-SW and E-W. Relative and absolute dating of the activated faults for each Shmax shows that the clearly
predominant N-S paleostress field in the zone has been active since the Oligocene up to the present day; while
a NE-SW stress field is found to have been active during the Cretaceous and an older E-W paleostress field
was active in the earlier Alpine cycle (Late Triassic).