A review of Late Cretaceous to Quaternary palaeogeography of the southern Andes

FOLGUERA, A.; ORTS, D.L.; SPAGNUOLO, M.; ROJAS VERA, E.; LITVAK, V.; SAGRIPANTI, L.; RAMOS, M.E.; RAMOS, V.A.

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 vol. 103 p. 250 - 268

0024-4066

The southern Andes were created by two main cycles of shallow to flat subduction settings that were derived from steepening subduction zones starting in Late Cretaceous times. The first wave of contractional deformation and Andean uplift migrated through the continental interior as a result of two shallow subduction zones, one developed between 36 and 39°S and the other between 40 and 46°S, associated with the expansion of arc magmatism. In latest Cretaceous to Eocene times, its northernmost segment flattened, increasing the compression and uplift of mountains in the far foreland area, whereas, to the south, a steepening subduction zone provoked extensional collapse of vast sectors of the fold and thrust belt followed by within-plate magmatism. The whole area between 36 and 44°S retreated as a large steepening zone in late Oligocene times, inducing asthenosphere injection and the formation of large within-plate plateaux in the foreland zone, as well as narrow extensional basins induced by the incipient collapse of the fold and thrust belt hinterland zone. The late Miocene was characterized by the development of three shallow subduction zones that expanded differentially between 34°30′ and 50°S. These were again associated with arc expansions and lateral construction of the fold and thrust belt. Their evolution finished in Pliocene to Quaternary times with the eruption of within-plate plateaux and widespread extensional deformation that still governs important sectors of the present retroarc area. Finally, an incipient shallow subduction setting could have been developing between 35 and 39°S in the last 3 Ma associated with renewed Andean uplift at these latitudes. Cyclic shallow subduction in the southern Andes, and therefore repeated behaviour of constructional stages followed by collapsing ones associated with voluminous volcanism, could be the consequence of the cycle imposed by the docking of seismic ridges, one achieved in latest Cretaceous (?) to Eocene times and the other in late Miocene times. Other factors, such as the collision of highly serpentinized and therefore isostatically buoyant plateaux, associated with fracture oceanic zones, are also considered to trigger shallow subduction settings.