Southern Andean geometry and related tectonic evolution as the result of the different subducted slab shallow configurations experimented in the last 100 My

FOLGUERA, A.; ROJAS VERA, E.; ORTS, D.L.; SPAGNUOLO, M.; TOBAL, J.; RAMOS, M.E.; RAMOS V.A.

Oviedo

Congreso; VIII Congreso Geológico de España; 2012

Sociedad Geológica de España

The southern Andes have been built through the stacking of crustal sheets in discrete periods during the last 100 My. The first important shortening took place in Late Cretaceous at the time of eastward arc expansions potentially linked to three areas of subducted slab shallowings of 200 and 800 km wide respectively. These shallowings have progressed to two smaller flat slabs in Eocene times, where rather anhydrous subducted slabs generated a discontinuous arc emplaced in the foreland area. Discrete segments of the former Late Cretaceous slab shallowings would have fallen down at this time producing early slab steepening settings. Then Late Oligocene times coincide with the final steepening of the broad Late Cretaceous to Eocene shallow subduction zone with the emplacement of voluminous volcanic plateaux in central Patagonia and extensional basins in the hinterland zone. Lately a long quiescence period was interrupted by the development of three Miocene shallow subduction settings more than 400 km long each, evidenced by arc expansions and associated with Andean uplift. Most of these areas were extensionally reactivated in the last 5 My at the time of retraction and steepening of formerly shallow subduction zones, being associated with voluminous mantle derived materials.