Have the southernmost Andes been curved since Late Cretaceous time? An analog test for the Patagonian Orocline

MATIAS C. GHIGLIONE; ERNESTO O. CRISTALLINI

GEOLOGY

Geological Society of America

Año: 2007 vol. 35 p. 13 - 16

0091-7613

The kinematic evolution of the enigmatic arc-shaped southernmostAndes of Patagonia and Tierra del Fuego has been a subject ofdebate for most of the past century. We compared the results fromanalog sandbox experiments with the tectonic evolution and actualconfi guration of the mountain chain in order to elucidate whetheroroclinal bending took place during the Tertiary, or if the southernmostAndes have been a curved orogen since at least Late Cretaceoustime. Experiments simulating oroclinal rotation producedstrong along-strike variations in shortening and failed to accountfor structural data compiled from the Fuegian Andes. Results fromexperiments simulating an L-shaped, concave-to-foreland indenterwere in agreement with the known Tertiary structural evolution ofthe southernmost Andes. The diachronicity of principal shorteningevents previously recognized in Patagonia and Tierra del Fuego couldonly be reproduced by moving the indenter in two successive orthogonaldirections: fi rst approximately northward to form the Fuegianfold-and-thrust belt, and then approximately eastward to propagatethrusting in the Patagonian Andes. This two-phase evolution is consistentwith a recorded change in the convergence direction of theFarallon-Nazca plate that occurred at ca. 27 Ma.