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Richards et al. 2004
Richards, D.R., Butler, R.F. and Sempere, T. (2004). Vertical-axis rotations determined from paleomagnetism of Mesozoic and Cenozoic strata of the Bolivian Andes. Journal of Geophysical Research 109: doi: 10.1029/2004JB002977. issn: 0148-0227.

Thermal demagnetization and principal component analysis allowed determination of characteristic remanent magnetization (ChRM) directions from 256 sites at 22 localities in Mesozoic and Cenozoic sedimentary strata of the Bolivian Altiplano and Eastern Cordillera. An inclination-only fold test of site-mean ChRM directions from Cenozoic units (principally the Santa Luc¿a Formation) indicates optimum unfolding at 97.1% unfolding, consistent with a primary origin for the ChRM. For Mesozoic strata, optimum unfolding occurred at 89.2%, perhaps indicating secondary remagnetization at some locations. For Cenozoic units, comparison of locality-mean directions with expected paleomagnetic directions indicates vertical-axis rotations from 33¿ counterclockwise to 24¿ clockwise. Euler pole analysis of along-strike variation in crustal shortening within the Subandean and Interandean zones indicates 18¿ clockwise rotation south of the axis of curvature of the Bolivian Andes and 6¿ counterclockwise rotation northwest of the axis during the past 10 m.y. Along-strike variation of shortening within the Eastern Cordillera indicates 8¿ clockwise rotation south of the axis and 8¿ counterclockwise rotation northwest of the axis from 35 to 10 Ma. These vertical-axis rotations produced by along-strike variations in crustal shortening during development of the Bolivian fold-thrust belt agree well with observed rotations determined from paleomagnetism of Cenozoic rocks in the Eastern Cordillera and in the Subandean and Interandean zones. However, local rotations are required to account for complex rotations in the Cochabamba Basin and within the Altiplano. The curvature of the Bolivian Andes has been progressively enhanced during Cenozoic fold-thrust belt deformation.

BACKGROUND DATA FILES

Abstract

Keywords
Geomagnetism and Paleomagnetism, Paleomagnetism applied to tectonics (regional, global), Tectonophysics, Continental contractional orogenic belts, Tectonophysics, Stresses—crust and lithosphere, Information Related to Geographic Region, South America, Information Related to Geologic Time, Cenozoic, tectonics, paleomagnetism, South America, Cenozoic, Bolivia
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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