Roperch Pierrich auteur aut IRD Carlotto V. auteur aut IRD Ruffet G. auteur aut IRD Fornari Michel auteur aut IRD text journalArticle eng text/pdf born digital access We report new paleomagnetic results from 55 out of 76 sites sampled at different localities along a transect from Nazca to Cuzco where the general structures of the Peruvian Andes are strongly offset across the Abancay deflection. Nine new Ar-39/Ar-40 ages better constrain the timing of volcanism along the western edge of the Western Cordillera at the latitude of Nazca. A mean paleomagnetic result from 22 sites in the lower Miocene volcanics does not show significant rotation (R = -2.3 degrees +/- 7.7 degrees) of the western margin of the Central Andean Plateau since the early Miocene. Within the Western Cordillera we sampled three structural blocks bounded to the north by the Abancay fault system. In the westernmost block, a large counterclockwise rotation (R = -65.0 degrees +/- 11.1 degrees) is found in Mesozoic limestones and Paleocene-Eocene red beds. Magnitude of rotation decreases toward the east from (R = -35.6 degrees +/- 12.8 degrees) in the central block to (R = -4.5 degrees +/- 8.4 degrees) south of the town of Cuzco. The anisotropy of magnetic susceptibility (AMS) recorded by the red beds sediments is the consequence of compaction and tectonic strain during the early stages of deformation. We show that the magnetic lineations were also rotated counterclockwise as the remanent magnetizations. The present study confirms results from the Peruvian fore arc, showing that rotations are not older than circa 40 Ma and likely not younger than circa 20 Ma. The spatial variation in the amount of counterclockwise rotation suggests a large component of shear along the Abancay deflection concomitant with a broad late Eocene-Oligocene oroclinal deformation in southern Peru. specialized 064 30 TC2010 [23 ] 2011 0278-7407 https://www.documentation.ird.fr/hor/PAR00007529 10.1029/2010tc002725 0278-7407 [F B010097280] https://www.documentation.ird.fr/hor/PAR00007529 https://www.documentation.ird.fr/intranet/publi/2026-06/010097280.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2011-05-31 2026-06-02 PAR00007529 fre