The control of pre-existing extensional structures in the evolution of the southern sector of the Aconcagua fold and thrust belt.

GIAMBIAGI, L., ALVAREZ, P., GODOY, E. Y RAMOS, V.

TECTONOPHYSICS

Elsevier

Año: 2003 vol. 369 p. 1 - 19

0040-1951

The Aconcagua fold and thrust belt, located in the Andean mountains at 32º30´ to 34° s.l., has been described as a classic model of a thin-skinned thrust belt. However, new structural data from its southern sector have shown that it has a complex structural framework reflected in multiple Mesozoic extensional phases, overprinted by structural inversion, as well as thin- and thick-skinned tectonics. Two major superimposed extensional structural styles have been identified for the Mesozoic, characterized by distinctly oriented stress fields. A key role in the evolution of this part of the fold and thrust belt was played by a Late Triassic to Early Jurassic depocentre and by Late Jurassic block-faulting. Shortening was accommodated by a combination of inversion of pre-existing normal faults, development of footwall short-cuts and both thin and thick-skinned thrusting. Synrift and postrift sedimentary rocks were uplifted by reactivation of normal faults, with further shortening along newly formed thin-skinned thrust faults. The geometry of thin-skinned fault systems is controlled by the architecture of the rift basin, competent footwalls forming barriers to the lateral propagation of detachments.