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

Abstract

This chapter is focused on the tectonic evolution of the North Patagonian Andes comprised between 38° and 40°S. Field recognition of main structures allowed establishing a structural control for the main sedimentary packages that coexisted with Andean development. These structures affect Miocene strata at the eastern deformational front, indicating a last stage of development, although cooling ages suggest a Mid to Late Cretaceous exhumation of the Paleozoic basement exposed at the westernmost sector. Synextensional deposits of late Oligocene age imply an interruption of Andean constructional mechanisms at these latitudes. Finally, seismic tomographies at these latitudes show an area of relatively low seismic velocities in the orogenic front area, separated from the arc front zone. Computed elastic thicknesses from gravity data show a good correlation with these areas with abnormal heat flow associated with retroarc stretching and magmatic emplacement in the last 5–2 Ma