A review of Late Cretaceous to Quaternary paleogeography of the Southern Andes. Patagonia Special Issue

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

Biological Journal of Linnean Society

Wiley

Año: 2011 p. 250 - 268

1095-8312

The Southern Andes were created by two main cycles of shallow to flat subduction settings that derived in steepening subduction zones starting in Late Cretaceous times. The first wave of contractional deformation and Andean uplift migrated through the continental interior due to two shallow subduction zones, one developed between 36º and 39ºS and the other between 40º and 46ºS, associated with expansion of arc magmatism. In Latest Cretaceous to Eocene times, its northernmost segment flattened increasing compression and uplifting 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 36º and 44ºS retreated as a large steepening zone in Late Oligocene times inducing asthenosphere injection and formation of large within plate plateaus in the foreland zone, as well as narrow extensional basins induced by the incipient collapse of the fold and thrust belt hinterland zone. Late Miocene is characterized by the development of three shallow subduction zones that expanded differentially between 34º30´and 50ºS. 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 irruption of within-plate plateaus and widespread extensional deformation that still governs important sectors of the present retroarc area. Finally, an incipient shallow subduction setting could be developing between 35º and 39ºS in the last 3 Ma associated with renewed Andean uplift at these latitudes. Cyclic shallow subduction in the Southern Andes and therefore repeated behavior 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 collision of highly serpentinized and therefore isostatically buoyant plateaus associated with fracture oceanic zones are also considered to trigger shallow subduction settings.