Tectonic Evolution of the Northern Patagonian Andes (40°S)

Abstract

This chapter is focused on the tectonic evolution of the North PatagonianAndes comprised between 38° and 40°S. Field recognition of main structuresallowed establishing a structural control for the main sedimentary packages thatcoexisted with Andean development. These structures affect Miocene strata at theeastern deformational front, indicating a last stage of development, althoughcooling ages suggest a Mid to Late Cretaceous exhumation of the Paleozoicbasement exposed at the westernmost sector. Synextensional deposits of lateOligocene age imply an interruption of Andean constructional mechanisms at theselatitudes. Finally, seismic tomographies at these latitudes show an area of relativelylow seismic velocities in the orogenic front area, separated from the arc front zone.Computed elastic thicknesses from gravity data show a good correlation with theseareas with abnormal heat flow associated with retroarc stretching and magmaticemplacement in the last 5-2 Ma.