Published 1995 as part of Memoir 62
Copyright © 1995 The American Association of Petroleum Geologists.   All Rights Reserved.

Structural data from the region of the bend in the Bolivian Andes at 17-19° S lat are integrated with paleogeographic data, paleomagnetic data, and data on the along-strike variation in crustal shortening. These data show that the bend in the mountain belt is due to a combination of (1) primary paleogeographic control on the eastern margin and within the mountain belt, (2) an inherited change in strike of the western margin, and (3) a variation in the amount of crustal shortening along strike, which leads to a synorogenic rotation of the western margin. The bend is not an orocline, but is rotational. The Cochabamba region is interpreted as an active, thin-skinned pull-apart basin, developed along tear faults that accommodate differential movement between thrust faults. Plunging folds, other tear faults, and arcuate fault traces suggest footwall morphology due to lateral variations in sedimentary thickness. These structures are interpreted as resulting from paleogeographic elements related to the structure of the Paleozoic basin. Previous models of the formation of the bend are summarized and considered in light of this synthesis. An implication is that the variation in shortening along strike may be accounted for by the paleogeography, that is, by the width of the basin in which décollement units were deposited, and may not require variations in slab dip or plate convergence.