HR: 15:30h
AN: GP23A-07    [Abstracts]
TI: Vertical-Axis Rotations Within the Peruvian Altiplano
AU: * Roperch, P
EM: pierrick.roperch@ird.fr
AF: IRD UR154-LMTG & Géosciences Rennes, Campus de Beaulieu, Rennes, 35042, France
AU: Carlotto, V
EM: vcarlotto@ingemmet.gob.pe
AF: INGEMMET, Av. Canadá 1470, Lima, Peru
AB: During the last two decades, numerous paleomagnetic studies have reported tectonic rotations in the Central Andes but only few data are available for a key tectonic region like the southern Peruvian Altiplano. Clockwise rotations (> 25°) are recorded in Mesozoic to Early Paleogene rocks along the forearc of northern Chile (23-28°S) [Arriagada et al., 2006, Tectonics, doi:10.1029/2005TC001923]. Within the forearc of southern Peru, counterclockwise rotations recorded by flat lying red-beds (Moquegua Formation) increase from south to north from about -30° to more than -45° and rotations decrease with time from late Eocene to late Oligocene - early Miocene time [Roperch et al., 2006, Tectonics, doi:10.1029/2005TC001882]. Rotations in the forearc seems concomitant with deformation localized in the Eastern Cordillera. We speculate that the rotations within the forearc are related to shortening to the east of the Altiplano leading to the first stage of oroclinal bending. If this model is correct, rotations within the Altiplano should have similar magnitude than those of the forearc. We have undertaken a new paleomagnetic sampling (490 samples) along a transect from Nazca (8 sites in the early Miocene Nazca ignimbrites and 7 sites in Oligocene volcanics near Puquio, Western Altiplano) to Abancay (8 sites in Paleocene - Eocene red beds and dikes, Central Altiplano) and Cusco (20 sites in Eocene - Oligocene red beds, Eastern Altiplano). We will present the new results and discuss the spatial and temporal distribution of the tectonic rotations within the Andes of southern Peru.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 8000 STRUCTURAL GEOLOGY
DE: 8108 Continental tectonics: compressional
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Joint Assembly